101
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Hara SA, Kim BJ, Kuo JTW, Lee CD, Meng E, Pikov V. Long-term stability of intracortical recordings using perforated and arrayed Parylene sheath electrodes. J Neural Eng 2016; 13:066020. [DOI: 10.1088/1741-2560/13/6/066020] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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102
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Li Y, Deng J, Zhou J, Li X. Elastic and viscoelastic mechanical properties of brain tissues on the implanting trajectory of sub-thalamic nucleus stimulation. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2016; 27:163. [PMID: 27646405 DOI: 10.1007/s10856-016-5775-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 09/02/2016] [Indexed: 06/06/2023]
Abstract
Corresponding to pre-puncture and post-puncture insertion, elastic and viscoelastic mechanical properties of brain tissues on the implanting trajectory of sub-thalamic nucleus stimulation are investigated, respectively. Elastic mechanical properties in pre-puncture are investigated through pre-puncture needle insertion experiments using whole porcine brains. A linear polynomial and a second order polynomial are fitted to the average insertion force in pre-puncture. The Young's modulus in pre-puncture is calculated from the slope of the two fittings. Viscoelastic mechanical properties of brain tissues in post-puncture insertion are investigated through indentation stress relaxation tests for six interested regions along a planned trajectory. A linear viscoelastic model with a Prony series approximation is fitted to the average load trace of each region using Boltzmann hereditary integral. Shear relaxation moduli of each region are calculated using the parameters of the Prony series approximation. The results show that, in pre-puncture insertion, needle force almost increases linearly with needle displacement. Both fitting lines can perfectly fit the average insertion force. The Young's moduli calculated from the slope of the two fittings are worthy of trust to model linearly or nonlinearly instantaneous elastic responses of brain tissues, respectively. In post-puncture insertion, both region and time significantly affect the viscoelastic behaviors. Six tested regions can be classified into three categories in stiffness. Shear relaxation moduli decay dramatically in short time scales but equilibrium is never truly achieved. The regional and temporal viscoelastic mechanical properties in post-puncture insertion are valuable for guiding probe insertion into each region on the implanting trajectory.
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Affiliation(s)
- Yan Li
- Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, Department of Mechanical Engineering, Shandong University, Jinan, 250061, PR China
| | - Jianxin Deng
- Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, Department of Mechanical Engineering, Shandong University, Jinan, 250061, PR China.
| | - Jun Zhou
- Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, Department of Mechanical Engineering, Shandong University, Jinan, 250061, PR China.
| | - Xueen Li
- Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, 250012, PR China
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103
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Eles JR, Vazquez AL, Snyder NR, Lagenaur C, Murphy MC, Kozai TDY, Cui XT. Neuroadhesive L1 coating attenuates acute microglial attachment to neural electrodes as revealed by live two-photon microscopy. Biomaterials 2016; 113:279-292. [PMID: 27837661 DOI: 10.1016/j.biomaterials.2016.10.054] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 10/26/2016] [Accepted: 10/30/2016] [Indexed: 12/15/2022]
Abstract
Implantable neural electrode technologies for chronic neural recordings can restore functional control to paralysis and limb loss victims through brain-machine interfaces. These probes, however, have high failure rates partly due to the biological responses to the probe which generate an inflammatory scar and subsequent neuronal cell death. L1 is a neuronal specific cell adhesion molecule and has been shown to minimize glial scar formation and promote electrode-neuron integration when covalently attached to the surface of neural probes. In this work, the acute microglial response to L1-coated neural probes was evaluated in vivo by implanting coated devices into the cortex of mice with fluorescently labeled microglia, and tracking microglial dynamics with multi-photon microscopy for the ensuing 6 h in order to understand L1's cellular mechanisms of action. Microglia became activated immediately after implantation, extending processes towards both L1-coated and uncoated control probes at similar velocities. After the processes made contact with the probes, microglial processes expanded to cover 47.7% of the control probes' surfaces. For L1-coated probes, however, there was a statistically significant 83% reduction in microglial surface coverage. This effect was sustained through the experiment. At 6 h post-implant, the radius of microglia activation was reduced for the L1 probes by 20%, shifting from 130.0 to 103.5 μm with the coating. Microglia as far as 270 μm from the implant site displayed significantly lower morphological characteristics of activation for the L1 group. These results suggest that the L1 surface treatment works in an acute setting by microglial mediated mechanisms.
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Affiliation(s)
- James R Eles
- Bioengineering, University of Pittsburgh, United States; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, United States
| | - Alberto L Vazquez
- Bioengineering, University of Pittsburgh, United States; Radiology, University of Pittsburgh, United States; Neurobiology, University of Pittsburgh, United States
| | - Noah R Snyder
- Bioengineering, University of Pittsburgh, United States; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, United States
| | - Carl Lagenaur
- Neurobiology, University of Pittsburgh, United States
| | | | - Takashi D Y Kozai
- Bioengineering, University of Pittsburgh, United States; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, United States; McGowan Institute for Regenerative Medicine, University of Pittsburgh, United States; NeuroTech Center of the University of Pittsburgh Brain Institute, United States.
| | - X Tracy Cui
- Bioengineering, University of Pittsburgh, United States; Center for the Neural Basis of Cognition, University of Pittsburgh and Carnegie Mellon University, United States; McGowan Institute for Regenerative Medicine, University of Pittsburgh, United States.
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104
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Sohal HS, Clowry GJ, Jackson A, O’Neill A, Baker SN. Mechanical Flexibility Reduces the Foreign Body Response to Long-Term Implanted Microelectrodes in Rabbit Cortex. PLoS One 2016; 11:e0165606. [PMID: 27788240 PMCID: PMC5082854 DOI: 10.1371/journal.pone.0165606] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 10/15/2016] [Indexed: 02/04/2023] Open
Abstract
Micromotion between the brain and implanted electrodes is a major contributor to the failure of invasive microelectrodes. Movements of the electrode tip cause recording instabilities while spike amplitudes decline over the weeks/months post-implantation due to glial cell activation caused by sustained mechanical trauma. We compared the glial response over a 26-96 week period following implantation in the rabbit cortex of microwires and a novel flexible electrode. Horizontal sections were used to obtain a depth profile of the radial distribution of microglia, astrocytes and neurofilament. We found that the flexible electrode was associated with decreased gliosis compared to the microwires over these long indwelling periods. This was in part due to a decrease in overall microgliosis and enhanced neuronal density around the flexible probe, especially at longer periods of implantation.
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Affiliation(s)
- Harbaljit S. Sohal
- Center for Bioelectronic Medicine, Feinstein Institute for Medical Research, Manhassett, NY, 11030, United States of America
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, NE2 4HH, United Kingdom
| | - Gavin J. Clowry
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, NE2 4HH, United Kingdom
| | - Andrew Jackson
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, NE2 4HH, United Kingdom
| | - Anthony O’Neill
- School of Electrical and Electronic Engineering, Newcastle University, Newcastle Upon Tyne, NE1 7RU, United Kingdom
| | - Stuart N. Baker
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, NE2 4HH, United Kingdom
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105
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Khilwani R, Gilgunn PJ, Kozai TDY, Ong XC, Korkmaz E, Gunalan PK, Cui XT, Fedder GK, Ozdoganlar OB. Ultra-miniature ultra-compliant neural probes with dissolvable delivery needles: design, fabrication and characterization. Biomed Microdevices 2016; 18:97. [DOI: 10.1007/s10544-016-0125-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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106
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Moatsou D, Weder C. Mechanically Adaptive Nanocomposites Inspired by Sea Cucumbers. BIO-INSPIRED POLYMERS 2016. [DOI: 10.1039/9781782626664-00402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Sea cucumbers own the fascinating capability to rapidly and reversibly change the stiffness of their dermis. This mechanical morphing is achieved through a distinctive architecture of the tissue, which is composed of a viscoelastic matrix that is reinforced with rigid collagen microfibrils. Neurosecretory proteins regulate the interactions among the latter, and thereby control the overall mechanical properties of the material. This architecture and functionality have been mimicked by researchers in artificial nanocomposites that feature similar, albeit significantly simplified, structure and mechanical morphing ability. The general design of such stimulus–responsive, mechanically adaptive materials involves a low-modulus polymer matrix and rigid, high-aspect ratio filler particles, which are arranged to form percolating networks within the polymer matrix. Stress transfer is controlled by switching the interactions among the nanofibers and/or between the nanofibers and the matrix polymer via an external stimulus. In first embodiments, water was employed to moderate hydrogen-bonding interactions in such nanocomposites, while more recent examples have been designed to respond to more specific stimuli, such as a change of the pH, or irradiation with ultraviolet light. This chapter provides an overview of the general design principles and materials embodiments of such sea-cucumber inspired materials.
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Affiliation(s)
- Dafni Moatsou
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Christoph Weder
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
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107
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Flexible, Penetrating Brain Probes Enabled by Advances in Polymer Microfabrication. MICROMACHINES 2016; 7:mi7100180. [PMID: 30404353 PMCID: PMC6190320 DOI: 10.3390/mi7100180] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 09/19/2016] [Indexed: 12/13/2022]
Abstract
The acquisition of high-fidelity, long-term neural recordings in vivo is critically important to advance neuroscience and brain⁻machine interfaces. For decades, rigid materials such as metal microwires and micromachined silicon shanks were used as invasive electrophysiological interfaces to neurons, providing either single or multiple electrode recording sites. Extensive research has revealed that such rigid interfaces suffer from gradual recording quality degradation, in part stemming from tissue damage and the ensuing immune response arising from mechanical mismatch between the probe and brain. The development of "soft" neural probes constructed from polymer shanks has been enabled by advancements in microfabrication; this alternative has the potential to mitigate mismatch-related side effects and thus improve the quality of recordings. This review examines soft neural probe materials and their associated microfabrication techniques, the resulting soft neural probes, and their implementation including custom implantation and electrical packaging strategies. The use of soft materials necessitates careful consideration of surgical placement, often requiring the use of additional surgical shuttles or biodegradable coatings that impart temporary stiffness. Investigation of surgical implantation mechanics and histological evidence to support the use of soft probes will be presented. The review concludes with a critical discussion of the remaining technical challenges and future outlook.
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108
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Neural Probes for Chronic Applications. MICROMACHINES 2016; 7:mi7100179. [PMID: 30404352 PMCID: PMC6190051 DOI: 10.3390/mi7100179] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 09/12/2016] [Accepted: 09/26/2016] [Indexed: 12/11/2022]
Abstract
Developed over approximately half a century, neural probe technology is now a mature technology in terms of its fabrication technology and serves as a practical alternative to the traditional microwires for extracellular recording. Through extensive exploration of fabrication methods, structural shapes, materials, and stimulation functionalities, neural probes are now denser, more functional and reliable. Thus, applications of neural probes are not limited to extracellular recording, brain-machine interface, and deep brain stimulation, but also include a wide range of new applications such as brain mapping, restoration of neuronal functions, and investigation of brain disorders. However, the biggest limitation of the current neural probe technology is chronic reliability; neural probes that record with high fidelity in acute settings often fail to function reliably in chronic settings. While chronic viability is imperative for both clinical uses and animal experiments, achieving one is a major technological challenge due to the chronic foreign body response to the implant. Thus, this review aims to outline the factors that potentially affect chronic recording in chronological order of implantation, summarize the methods proposed to minimize each factor, and provide a performance comparison of the neural probes developed for chronic applications.
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109
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Feicht SE, Khair AS. A mathematical model for electrical impedance spectroscopy of zwitterionic hydrogels. SOFT MATTER 2016; 12:7028-7037. [PMID: 27464763 DOI: 10.1039/c6sm01445c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report a mathematical model for ion transport and electrical impedance in zwitterionic hydrogels, which possess acidic and basic functional groups that carry a net charge at a pH not equal to the isoelectric point. Such hydrogels can act as an electro-mechanical interface between a relatively hard biosensor and soft tissue in the body. For this application, the electrical impedance of the hydrogel must be characterized to ensure that ion transport to the biosensor is not significantly hindered. The electrical impedance is the ratio of the applied voltage to the measured current. We consider a simple model system, wherein an oscillating voltage is applied across a hydrogel immersed in electrolyte and sandwiched between parallel, blocking electrodes. We employ the Poisson-Nernst-Planck (PNP) equations coupled with acid-base dissociation reactions for the charge on the hydrogel backbone to model the ionic transport across the hydrogel. The electrical impedance is calculated from the numerical solution to the PNP equations and subsequently analyzed via an equivalent circuit model to extract the hydrogel capacitance, resistance, and the capacitance of electrical double layers at the electrode-hydrogel interface. For example, we predict that an increase in pH from the isoelectric point, pH = 6.4 for a model PCBMA hydrogel, to pH = 8 reduces the resistance of the hydrogel by ∼40% and increases the double layer capacitance by ∼250% at an electrolyte concentration of 0.1 mM. The significant impact of charged hydrogel functional groups to the impedance is damped at higher electrolyte concentration.
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Affiliation(s)
- Sarah E Feicht
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
| | - Aditya S Khair
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
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110
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Reit R, Abitz H, Reddy N, Parker S, Wei A, Aragon N, Ho M, Weittenhiller A, Kang T, Ecker M, Voit WE. Thiol-epoxy/maleimide ternary networks as softening substrates for flexible electronics. J Mater Chem B 2016; 4:5367-5374. [PMID: 32263460 DOI: 10.1039/c6tb01082b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Softening microelectrode arrays, or flexible bioelectronic systems which can dynamically change modulus under the application of an external stimulus such as heat or electromagnetic radiation, have been of significant interest in the literature within the previous decade. Through their ability to actively soften in vivo, these devices have shown the capacity to attenuate the neuronal damage associated with insertion of rigid microelectrode arrays into soft tissue. Thiol-click substrates specifically have shown particularly impressive results for fabricating devices requiring small-scale, high-performance electronics for neural recording. However, previous attempts to engineer increasingly lower-modulus substrates for these devices have failed due to the fundamental chemistries' (the thioether linkage) flexibility. This failure has led to substrates without sufficient mechanical rigidity for penetrating soft tissue at physiological temperatures, or sufficient softening capacity to reduce the mechanical mismatch between soft tissue and implantable device. In this work, a ternary thiol-epoxy/maleimide network is investigated as a potential substrate materials space in which the degree of softening can be modulated without sacrificing the mechanical rigidity at physiological temperatures. Using these networks as platforms for the microfabrication of electrode arrays, example implantable intracortical microelectrode arrays are fabricated on both thiol-epoxy and thiol-epoxy/maleimide networks to demonstrate the insertion capacity of microelectrode arrays on the ternary polymer networks.
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Affiliation(s)
- Radu Reit
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX 75030, USA.
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111
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Computational Assessment of Neural Probe and Brain Tissue Interface under Transient Motion. BIOSENSORS-BASEL 2016; 6:27. [PMID: 27322338 PMCID: PMC4931487 DOI: 10.3390/bios6020027] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 01/25/2023]
Abstract
The functional longevity of a neural probe is dependent upon its ability to minimize injury risk during the insertion and recording period in vivo, which could be related to motion-related strain between the probe and surrounding tissue. A series of finite element analyses was conducted to study the extent of the strain induced within the brain in an area around a neural probe. This study focuses on the transient behavior of neural probe and brain tissue interface with a viscoelastic model. Different stages of the interface from initial insertion of neural probe to full bonding of the probe by astro-glial sheath formation are simulated utilizing analytical tools to investigate the effects of relative motion between the neural probe and the brain while friction coefficients and kinematic frequencies are varied. The analyses can provide an in-depth look at the quantitative benefits behind using soft materials for neural probes.
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112
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Engineering and commercialization of human-device interfaces, from bone to brain. Biomaterials 2016; 95:35-46. [PMID: 27108404 DOI: 10.1016/j.biomaterials.2016.03.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 03/16/2016] [Accepted: 03/28/2016] [Indexed: 12/16/2022]
Abstract
Cutting edge developments in engineering of tissues, implants and devices allow for guidance and control of specific physiological structure-function relationships. Yet the engineering of functionally appropriate human-device interfaces represents an intractable challenge in the field. This leading opinion review outlines a set of current approaches as well as hurdles to design of interfaces that modulate transfer of information, i.a. forces, electrical potentials, chemical gradients and haptotactic paths, between endogenous and engineered body parts or tissues. The compendium is designed to bridge across currently separated disciplines by highlighting specific commonalities between seemingly disparate systems, e.g. musculoskeletal and nervous systems. We focus on specific examples from our own laboratories, demonstrating that the seemingly disparate musculoskeletal and nervous systems share common paradigms which can be harnessed to inspire innovative interface design solutions. Functional barrier interfaces that control molecular and biophysical traffic between tissue compartments of joints are addressed in an example of the knee. Furthermore, we describe the engineering of gradients for interfaces between endogenous and engineered tissues as well as between electrodes that physically and electrochemically couple the nervous and musculoskeletal systems. Finally, to promote translation of newly developed technologies into products, protocols, and treatments that benefit the patients who need them most, regulatory and technical challenges and opportunities are addressed on hand from an example of an implant cum delivery device that can be used to heal soft and hard tissues, from brain to bone.
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113
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Pisanello F, Sileo L, De Vittorio M. Micro- and Nanotechnologies for Optical Neural Interfaces. Front Neurosci 2016; 10:70. [PMID: 27013939 PMCID: PMC4781845 DOI: 10.3389/fnins.2016.00070] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 02/15/2016] [Indexed: 12/11/2022] Open
Abstract
In last decade, the possibility to optically interface with the mammalian brain in vivo has allowed unprecedented investigation of functional connectivity of neural circuitry. Together with new genetic and molecular techniques to optically trigger and monitor neural activity, a new generation of optical neural interfaces is being developed, mainly thanks to the exploitation of both bottom-up and top-down nanofabrication approaches. This review highlights the role of nanotechnologies for optical neural interfaces, with particular emphasis on new devices and methodologies for optogenetic control of neural activity and unconventional methods for detection and triggering of action potentials using optically-active colloidal nanoparticles.
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Affiliation(s)
- Ferruccio Pisanello
- Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia Lecce, Italy
| | - Leonardo Sileo
- Dipartimento di Ingegneria dell'Innovazione, Università del Salento Lecce, Italy
| | - Massimo De Vittorio
- Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia Lecce, Italy
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114
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Modeling the Insertion Mechanics of Flexible Neural Probes Coated with Sacrificial Polymers for Optimizing Probe Design. SENSORS 2016; 16:s16030330. [PMID: 26959021 PMCID: PMC4813905 DOI: 10.3390/s16030330] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 02/18/2016] [Accepted: 02/29/2016] [Indexed: 01/20/2023]
Abstract
Single-unit recording neural probes have significant advantages towards improving signal-to-noise ratio and specificity for signal acquisition in brain-to-computer interface devices. Long-term effectiveness is unfortunately limited by the chronic injury response, which has been linked to the mechanical mismatch between rigid probes and compliant brain tissue. Small, flexible microelectrodes may overcome this limitation, but insertion of these probes without buckling requires supporting elements such as a stiff coating with a biodegradable polymer. For these coated probes, there is a design trade-off between the potential for successful insertion into brain tissue and the degree of trauma generated by the insertion. The objective of this study was to develop and validate a finite element model (FEM) to simulate insertion of coated neural probes of varying dimensions and material properties into brain tissue. Simulations were performed to predict the buckling and insertion forces during insertion of coated probes into a tissue phantom with material properties of brain. The simulations were validated with parallel experimental studies where probes were inserted into agarose tissue phantom, ex vivo chick embryonic brain tissue, and ex vivo rat brain tissue. Experiments were performed with uncoated copper wire and both uncoated and coated SU-8 photoresist and Parylene C probes. Model predictions were found to strongly agree with experimental results (<10% error). The ratio of the predicted buckling force-to-predicted insertion force, where a value greater than one would ideally be expected to result in successful insertion, was plotted against the actual success rate from experiments. A sigmoidal relationship was observed, with a ratio of 1.35 corresponding to equal probability of insertion and failure, and a ratio of 3.5 corresponding to a 100% success rate. This ratio was dubbed the “safety factor”, as it indicated the degree to which the coating should be over-designed to ensure successful insertion. Probability color maps were generated to visually compare the influence of design parameters. Statistical metrics derived from the color maps and multi-variable regression analysis confirmed that coating thickness and probe length were the most important features in influencing insertion potential. The model also revealed the effects of manufacturing flaws on insertion potential.
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115
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Nguyen JK, Jorfi M, Buchanan KL, Park DJ, Foster EJ, Tyler DJ, Rowan SJ, Weder C, Capadona JR. Influence of resveratrol release on the tissue response to mechanically adaptive cortical implants. Acta Biomater 2016; 29:81-93. [PMID: 26553391 PMCID: PMC4727752 DOI: 10.1016/j.actbio.2015.11.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/05/2015] [Accepted: 11/02/2015] [Indexed: 01/10/2023]
Abstract
The stability and longevity of recordings obtained from intracortical microelectrodes continues to remain an area of concern for neural interfacing applications. The limited longevity of microelectrode performance has been associated with the integrity of the blood brain barrier (BBB) and the neuroinflammatory response to the microelectrode. Here, we report the investigation of an additive approach that targets both mechanical and chemical factors believed to contribute to chronic BBB instability and the neuroinflammatory response associated with implanted intracortical microelectrodes. The implants investigated were based on a mechanically adaptive, compliant nanocomposite (NC), which reduces the tissue response and tissue strain. This material was doped with various concentrations of the antioxidant resveratrol with the objective of local and rapid delivery. In vitro analysis of resveratrol release, antioxidant activity, and cytotoxicity suggested that a resveratrol content of 0.01% was optimal for in vivo assessment. Thus, probes made from the neat NC reference and probes containing resveratrol (NC Res) were implanted into the cortical tissue of rats for up to sixteen weeks. Histochemical analysis suggested that at three days post-implantation, neither materials nor therapeutic approaches (independently or in combination) could alter the initial wound healing response. However, at two weeks post-implantation, the NC Res implant showed a reduction in activated microglia/macrophages and improvement in neuron density at the tissue-implant interface when compared to the neat NC reference. However, sixteen weeks post-implantation, when the antioxidant was exhausted, NC Res and the neat NC reference exhibited similar tissue responses. The data show that NC Res provides short-term, short-lived benefits due to the antioxidant release, and a long-term reduction in neuroinflammation on account of is mechanical adaptive, compliant nature. Together, these results demonstrate that local delivery of resveratrol can provide an additive advantage by providing a consistent reduction in the tissue response.
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Affiliation(s)
- Jessica K Nguyen
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr. Drive, Wickenden Bldg, Cleveland, OH 44106, USA; Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd, 151 W/APT, Cleveland, OH 44106-1702, USA
| | - Mehdi Jorfi
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland
| | - Kelly L Buchanan
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr. Drive, Wickenden Bldg, Cleveland, OH 44106, USA; Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd, 151 W/APT, Cleveland, OH 44106-1702, USA
| | - Daniel J Park
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr. Drive, Wickenden Bldg, Cleveland, OH 44106, USA
| | - E Johan Foster
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland; Virginia Tech, Department of Materials Science & Engineering & Macromolecules and Interfaces Institute, 445 Old Turner Street, 213 Holden Hall, Blacksburg, VA 24061, USA
| | - Dustin J Tyler
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr. Drive, Wickenden Bldg, Cleveland, OH 44106, USA; Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd, 151 W/APT, Cleveland, OH 44106-1702, USA
| | - Stuart J Rowan
- Department of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert Road, Kent Hale Smith Bldg, Cleveland, OH 44106-7202, USA
| | - Christoph Weder
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland
| | - Jeffrey R Capadona
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr. Drive, Wickenden Bldg, Cleveland, OH 44106, USA; Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd, 151 W/APT, Cleveland, OH 44106-1702, USA.
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116
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Reit R, Zamorano D, Parker S, Simon D, Lund B, Voit W, Ware TH. Hydrolytically Stable Thiol-ene Networks for Flexible Bioelectronics. ACS APPLIED MATERIALS & INTERFACES 2015; 7:28673-28681. [PMID: 26650346 DOI: 10.1021/acsami.5b10593] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Hydrolytically stable, tunable modulus polymer networks are demonstrated to survive harsh alkaline environments and offer promise for use in long-term implantable bioelectronic medicines known as electroceuticals. Today's polymer networks (such as polyimides or polysiloxanes) succeed in providing either stiff or soft substrates for bioelectronics devices; however, the capability to significantly tune the modulus of such materials is lacking. Within the space of materials with easily modified elastic moduli, thiol-ene copolymers are a subset of materials that offer a promising solution to build next generation flexible bioelectronics but have typically been susceptible to hydrolytic degradation chronically. In this inquiry, we demonstrate a materials space capable of tuning the substrate modulus and explore the mechanical behavior of such networks. Furthermore, we fabricate an array of microelectrodes that can withstand accelerated aging environments shown to destroy conventional flexible bioelectronics.
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Affiliation(s)
- Radu Reit
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Daniel Zamorano
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Shelbi Parker
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Dustin Simon
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Benjamin Lund
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Walter Voit
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
| | - Taylor H Ware
- Department of Bioengineering, ‡Department of Chemistry, §Department of Materials Science and Engineering, and ∥Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Mailstop RL 10, Richardson, Texas 75080, United States
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Arreaga-Salas DE, Avendaño-Bolívar A, Simon D, Reit R, Garcia-Sandoval A, Rennaker RL, Voit W. Integration of High-Charge-Injection-Capacity Electrodes onto Polymer Softening Neural Interfaces. ACS APPLIED MATERIALS & INTERFACES 2015; 7:26614-23. [PMID: 26575084 DOI: 10.1021/acsami.5b08139] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Softening neural interfaces are implanted stiff to enable precise insertion, and they soften in physiological conditions to minimize modulus mismatch with tissue. In this work, a high-charge-injection-capacity iridium electrode fabrication process is detailed. For the first time, this process enables integration of iridium electrodes onto softening substrates using photolithography to define all features in the device. Importantly, no electroplated layers are utilized, leading to a highly scalable method for consistent device fabrication. The iridium electrode is metallically bonded to the gold conductor layer, which is covalently bonded to the softening substrate via sulfur-based click chemistry. The resulting shape-memory polymer neural interfaces can deliver more than 2 billion symmetric biphasic pulses (100 μs/phase), with a charge of 200 μC/cm(2) and geometric surface area (GSA) of 300 μm(2). A transfer-by-polymerization method is used in combination with standard semiconductor processing techniques to fabricate functional neural probes onto a thiol-ene-based, thin film substrate. Electrical stability is tested under simulated physiological conditions in an accelerated electrical aging paradigm with periodic measurement of electrochemical impedance spectra (EIS) and charge storage capacity (CSC) at various intervals. Electrochemical characterization and both optical and scanning electron microscopy suggest significant breakdown of the 600 nm-thick parylene-C insulation, although no delamination of the conductors or of the final electrode interface was observed. Minor cracking at the edges of the thin film iridium electrodes was occasionally observed. The resulting devices will provide electrical recording and stimulation of the nervous system to better understand neural wiring and timing, to target treatments for debilitating diseases, and to give neuroscientists spatially selective and specific tools to interact with the body. This approach has uses for cochlear implants, nerve cuff electrodes, penetrating cortical probes, spinal stimulators, blanket electrodes for the gut, stomach, and visceral organs and a host of other custom nerve-interfacing devices.
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Affiliation(s)
- David E Arreaga-Salas
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Adrian Avendaño-Bolívar
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Dustin Simon
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Radu Reit
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Aldo Garcia-Sandoval
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Robert L Rennaker
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
| | - Walter Voit
- Department of Materials Science and Engineering, ‡Department of Bioengineering, and §Department of Mechanical Engineering, The University of Texas at Dallas , 800 West Campbell Road, Richardson, Texas 75080-3021, United States
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Abstract
Optogenetics is an exciting new technology that allows targetable fast control and readout of specific neural populations in complex brain circuits. With the rapid development of light-sensitive microbial opsins, substantial gains in understanding the causal relationships between neural activity and behavior in both healthy and diseased brains have been achieved during the last decade. However, the intricate and complex interactions between different neural populations in mammalian brains require novel, implantable, neural interfaces that are capable of manipulating and probing targeted neurons at multiple sites and with high spatiotemporal resolution. Advanced microtechnology has offered the highest potential to meet these demands of optogenetic applications. In this paper, we review a variety of miniaturized optogenetic neural implants developed in recent years, based on different light sources, including lasers, laser diodes, and light-emitting diodes. We then summarize the specifications of these microimplants and their related microfabrication approaches and discuss the major challenges of current techniques and the vision for the future of the field.
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Affiliation(s)
- B Fan
- Electrical and Computer Engineering Department, Michigan State University, East Lansing, MI 48824, USA.
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119
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Ejserholm F, Stegmayr J, Bauer P, Johansson F, Wallman L, Bengtsson M, Oredsson S. Biocompatibility of a polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+) for neural implants. Biomater Res 2015; 19:19. [PMID: 26396744 PMCID: PMC4578262 DOI: 10.1186/s40824-015-0041-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 09/04/2015] [Indexed: 11/10/2022] Open
Abstract
Background The flexibility of implantable neural probes has increased during the last 10 years, starting with stiff materials such as silicone to more flexible materials like polyimide. We have developed a novel polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+, consisting of a thiol, two allyls, an epoxy resin and two initiators), which is up to 100 times more flexible than polyimide. Since a flexible neural probe should be more biocompatible than a stiff probe, an OSTE+ probe should be more biocompatible than one composed of a more rigid material. We have investigated the toxicity of OSTE+ as well as of OSTE+ that had been incubated in water for a week (OSTE+H2O) using MTT assays with mouse L929 fibroblasts. We found that OSTE+ showed cytotoxicity, but OSTE+H2O did not. Extracts were analyzed using LC-MS and GC-MS in order to identify leaked chemicals. Results Most constituents were found in extracts of OSTE+, whereas only initiators were found in OSTE+H2O extracts. The detected levels of each chemical found in the LC-MS and the GC-MS analysis were below the toxicity level when compared to MTT assays of all the individual chemicals, except for one of the initiators that had an IC50 value close to the detected levels. Conclusion Our notion is that the toxicity of OSTE+ was caused by one of the initiators, by impurities in the constituents or by synergistic effects of low doses of leaked chemicals. However, our conclusion is that if OSTE+ is incubated for one week in water, OSTE+ is not cytotoxic and suitable for further in vivo studies.
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Affiliation(s)
- Fredrik Ejserholm
- Department of Biomedical Engineering, Lund University, Box 118, Lund, 221 00 Sweden ; NeuroNano Research Centre, Lund University, Medicon Village, Scheelevägen 8, Lund, 223 81 Sweden
| | - John Stegmayr
- Department of Laboratory Medicine, Lund University, Box 118, Lund, 221 00 Sweden ; Department of Biology, Lund University, Box 118, Lund, 221 00 Sweden
| | - Patrik Bauer
- Department of Biology, Lund University, Box 118, Lund, 221 00 Sweden
| | - Fredrik Johansson
- NeuroNano Research Centre, Lund University, Medicon Village, Scheelevägen 8, Lund, 223 81 Sweden ; Department of Biology, Lund University, Box 118, Lund, 221 00 Sweden
| | - Lars Wallman
- Department of Biomedical Engineering, Lund University, Box 118, Lund, 221 00 Sweden ; NeuroNano Research Centre, Lund University, Medicon Village, Scheelevägen 8, Lund, 223 81 Sweden
| | - Martin Bengtsson
- Department of Biomedical Engineering, Lund University, Box 118, Lund, 221 00 Sweden ; NeuroNano Research Centre, Lund University, Medicon Village, Scheelevägen 8, Lund, 223 81 Sweden
| | - Stina Oredsson
- Department of Biology, Lund University, Box 118, Lund, 221 00 Sweden
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120
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Jeong JW, McCall JG, Shin G, Zhang Y, Al-Hasani R, Kim M, Li S, Sim JY, Jang KI, Shi Y, Hong DY, Liu Y, Schmitz GP, Xia L, He Z, Gamble P, Ray WZ, Huang Y, Bruchas MR, Rogers JA. Wireless Optofluidic Systems for Programmable In Vivo Pharmacology and Optogenetics. Cell 2015; 162:662-74. [PMID: 26189679 PMCID: PMC4525768 DOI: 10.1016/j.cell.2015.06.058] [Citation(s) in RCA: 280] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 05/21/2015] [Accepted: 06/02/2015] [Indexed: 12/12/2022]
Abstract
In vivo pharmacology and optogenetics hold tremendous promise for dissection of neural circuits, cellular signaling, and manipulating neurophysiological systems in awake, behaving animals. Existing neural interface technologies, such as metal cannulas connected to external drug supplies for pharmacological infusions and tethered fiber optics for optogenetics, are not ideal for minimally invasive, untethered studies on freely behaving animals. Here, we introduce wireless optofluidic neural probes that combine ultrathin, soft microfluidic drug delivery with cellular-scale inorganic light-emitting diode (μ-ILED) arrays. These probes are orders of magnitude smaller than cannulas and allow wireless, programmed spatiotemporal control of fluid delivery and photostimulation. We demonstrate these devices in freely moving animals to modify gene expression, deliver peptide ligands, and provide concurrent photostimulation with antagonist drug delivery to manipulate mesoaccumbens reward-related behavior. The minimally invasive operation of these probes forecasts utility in other organ systems and species, with potential for broad application in biomedical science, engineering, and medicine.
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Affiliation(s)
- Jae-Woong Jeong
- Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, CO 80309, USA; Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Jordan G McCall
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA; Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Gunchul Shin
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yihui Zhang
- Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA; Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China
| | - Ream Al-Hasani
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA; Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Minku Kim
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Shuo Li
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Joo Yong Sim
- Bio-Medical IT Convergence Research Department, Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea
| | - Kyung-In Jang
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yan Shi
- Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA; State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Daniel Y Hong
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yuhao Liu
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Gavin P Schmitz
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Li Xia
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA
| | - Zhubin He
- Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA; School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Paul Gamble
- Department of Neurosurgery, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Wilson Z Ray
- Department of Neurosurgery, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yonggang Huang
- Departments of Civil and Environmental Engineering and Mechanical Engineering, Center for Engineering and Health, Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA
| | - Michael R Bruchas
- Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA; Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA.
| | - John A Rogers
- Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA; Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA; Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
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121
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Guex AA, Vachicouras N, Hight AE, Brown MC, Lee DJ, Lacour SP. Conducting polymer electrodes for auditory brainstem implants. J Mater Chem B 2015; 3:5021-5027. [PMID: 26207184 PMCID: PMC4507441 DOI: 10.1039/c5tb00099h] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The auditory brainstem implant (ABI) restores hearing in patients with damaged auditory nerves. One of the main ideas to improve the efficacy of ABIs is to increase spatial specificity of stimulation, in order to minimize extra-auditory side-effects and to maximize the tonotopy of stimulation. This study reports on the development of a microfabricated conformable electrode array with small (100 μm diameter) electrode sites. The latter are coated with a conducting polymer, PEDOT:PSS, to offer high charge injection properties and to safely stimulate the auditory system with small stimulation sites. We report on the design and fabrication of the polymer implant, and characterize the coatings in physiological conditions in vitro and under mechanical deformation. We characterize the coating electrochemically and during bending tests. We present a proof of principle experiment where the auditory system is efficiently activated by the flexible polymeric interface in a rat model. These results demonstrate the potential of using conducting polymer coatings on small electrode sites for electrochemically safe and efficient stimulation of the central auditory system.
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Affiliation(s)
- Amélie A. Guex
- Center for Neuroprosthetics, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
| | - Nicolas Vachicouras
- Center for Neuroprosthetics, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
| | - Ariel E. Hight
- Eaton-Peabody Laboratories and Department of Otolaryngology - Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
| | - M. Christian Brown
- Eaton-Peabody Laboratories and Department of Otolaryngology - Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
| | - Daniel J. Lee
- Eaton-Peabody Laboratories and Department of Otolaryngology - Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
| | - Stéphanie P. Lacour
- Center for Neuroprosthetics, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
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122
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Abstract
For implantable sensors to become a more viable option for continuous glucose monitoring strategies, they must be able to persist in vivo for periods longer than the 3- to 7-day window that is the current industry standard. Recent studies have attributed such limited performance to tissue reactions resulting from implantation. While in vivo biocompatibility studies have provided much in the way of understanding histology surrounding an implanted sensor, little is known about how each constituent of the foreign body response affects sensor function. Due to the ordered composition and geometry of implant-associated tissue reactions, their effects on sensor function may be computationally modeled and analyzed in a way that would be prohibitive using in vivo studies. This review both explains how physiologically accurate computational models of implant-associated tissue reaction can be designed and shows how they have been utilized thus far. Going forward, these in silico models of implanted sensor behavior may soon complement in vivo studies to provide valuable information for improved sensor designs.
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Affiliation(s)
- Matthew T Novak
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
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123
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Shen W, Karumbaiah L, Liu X, Saxena T, Chen S, Patkar R, Bellamkonda RV, Allen MG. Extracellular matrix-based intracortical microelectrodes: Toward a microfabricated neural interface based on natural materials. MICROSYSTEMS & NANOENGINEERING 2015; 1:15010. [PMID: 30498620 PMCID: PMC6258041 DOI: 10.1038/micronano.2015.10] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 05/10/2015] [Accepted: 05/15/2015] [Indexed: 05/16/2023]
Abstract
Extracellular matrix (ECM)-based implantable neural electrodes (NEs) were achieved using a microfabrication strategy on natural-substrate-based organic materials. The ECM-based design minimized the introduction of non-natural products into the brain. Further, it rendered the implants sufficiently rigid for penetration into the target brain region and allowed them subsequently to soften to match the elastic modulus of brain tissue upon exposure to physiological conditions, thereby reducing inflammatory strain fields in the tissue. Preliminary studies suggested that ECM-NEs produce a reduced inflammatory response compared with inorganic rigid and flexible approaches. In vivo intracortical recordings from the rat motor cortex illustrate one mode of use for these ECM-NEs.
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Affiliation(s)
- Wen Shen
- Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Krishna P. Singh Center for Nanotechnology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lohitash Karumbaiah
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory School of Medicine, Atlanta, GA 30332, USA
| | - Xi Liu
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Tarun Saxena
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory School of Medicine, Atlanta, GA 30332, USA
| | - Shuodan Chen
- Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Radhika Patkar
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory School of Medicine, Atlanta, GA 30332, USA
| | - Ravi V. Bellamkonda
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory School of Medicine, Atlanta, GA 30332, USA
| | - Mark G. Allen
- Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Krishna P. Singh Center for Nanotechnology, University of Pennsylvania, Philadelphia, PA 19104, USA
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124
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Kolarcik CL, Luebben SD, Sapp SA, Hanner J, Snyder N, Kozai TDY, Chang E, Nabity JA, Nabity ST, Lagenaur CF, Cui XT. Elastomeric and soft conducting microwires for implantable neural interfaces. SOFT MATTER 2015; 11:4847-61. [PMID: 25993261 PMCID: PMC4466039 DOI: 10.1039/c5sm00174a] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young's modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young's modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications.
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Affiliation(s)
- Christi L Kolarcik
- Department of Bioengineering, University of Pittsburgh, 5057 Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA, USA.
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125
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Lee JY, Khaing ZZ, Siegel JJ, Schmidt CE. Surface modification of neural electrodes with pyrrole-hyaluronic acid conjugate to attenuate reactive astrogliosis in vivo. RSC Adv 2015; 5:39228-39231. [PMID: 35528963 PMCID: PMC9075707 DOI: 10.1039/c5ra03294f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023] Open
Abstract
Surface of neural probes were electrochemically modified with a non-cell adhesive and biocompatible conjugate, pyrrole-hyaluronic acid (PyHA), to reduce reactive astrogliosis. Poly(PyHA)-modified wire electrodes were implanted into rat motor cortices for three weeks and were found to markedly reduce the expression of glial fibrillary acidic protein compared to uncoated electrodes.
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Affiliation(s)
- J Y Lee
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
- School of Materials Science and Engineering, Gwangju Institute of Science and Engineering, Gwangju, South Korea
| | - Z Z Khaing
- Department of Biomedical Engineering, The University of Florida at Gainesville, Gainesville, FL, USA
| | - J J Siegel
- Center for Learning and Memory, The University of Texas at Austin, Austin, TX, USA
| | - C E Schmidt
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX, USA
- Department of Biomedical Engineering, The University of Florida at Gainesville, Gainesville, FL, USA
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126
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Sridharan A, Nguyen JK, Capadona JR, Muthuswamy J. Compliant intracortical implants reduce strains and strain rates in brain tissue in vivo. J Neural Eng 2015; 12:036002. [PMID: 25834105 DOI: 10.1088/1741-2560/12/3/036002] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The objective of this research is to characterize the mechanical interactions of (1) soft, compliant and (2) non-compliant implants with the surrounding brain tissue in a rodent brain. Understanding such interactions will enable the engineering of novel materials that will improve stability and reliability of brain implants. APPROACH Acute force measurements were made using a load cell in n = 3 live rats, each with 4 craniotomies. Using an indentation method, brain tissue was tested for changes in force using established protocols. A total of 4 non-compliant, bare silicon microshanks, 3 non-compliant polyvinyl acetate (PVAc)-coated silicon microshanks, and 6 compliant, nanocomposite microshanks were tested. Stress values were calculated by dividing the force by surface area and strain was estimated using a linear stress-strain relationship. Micromotion effects from breathing and vascular pulsatility on tissue stress were estimated from a 5 s interval of steady-state measurements. Viscoelastic properties were estimated using a second-order Prony series expansion of stress-displacement curves for each shank. MAIN RESULTS The distribution of strain values imposed on brain tissue for both compliant nanocomposite microshanks and PVAc-coated, non-compliant silicon microshanks were significantly lower compared to non-compliant bare silicon shanks. Interestingly, step-indentation experiments also showed that compliant, nanocomposite materials significantly decreased stress relaxation rates in the brain tissue at the interface (p < 0.05) compared to non-compliant silicon and PVAc-coated silicon materials. Furthermore, both PVAc-coated non-compliant silicon and compliant nanocomposite shanks showed significantly reduced (by 4-5 fold) stresses due to tissue micromotion at the interface. SIGNIFICANCE The results of this study showed that soft, adaptive materials reduce strains and strain rates and micromotion induced stresses in the surrounding brain tissue. Understanding the material behavior at the site of tissue contact will help to improve neural implant design.
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Affiliation(s)
- Arati Sridharan
- School of Biological & Health Systems Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287, USA
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127
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Kozai TDY, Jaquins-Gerstl AS, Vazquez AL, Michael AC, Cui XT. Brain tissue responses to neural implants impact signal sensitivity and intervention strategies. ACS Chem Neurosci 2015; 6:48-67. [PMID: 25546652 PMCID: PMC4304489 DOI: 10.1021/cn500256e] [Citation(s) in RCA: 359] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
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Implantable biosensors are valuable
scientific tools for basic
neuroscience research and clinical applications. Neurotechnologies
provide direct readouts of neurological signal and neurochemical processes.
These tools are generally most valuable when performance capacities
extend over months and years to facilitate the study of memory, plasticity,
and behavior or to monitor patients’ conditions. These needs
have generated a variety of device designs from microelectrodes for
fast scan cyclic voltammetry (FSCV) and electrophysiology to microdialysis
probes for sampling and detecting various neurochemicals. Regardless
of the technology used, the breaching of the blood–brain barrier
(BBB) to insert devices triggers a cascade of biochemical pathways
resulting in complex molecular and cellular responses to implanted
devices. Molecular and cellular changes in the microenvironment surrounding
an implant include the introduction of mechanical strain, activation
of glial cells, loss of perfusion, secondary metabolic injury, and
neuronal degeneration. Changes to the tissue microenvironment surrounding
the device can dramatically impact electrochemical and electrophysiological
signal sensitivity and stability over time. This review summarizes
the magnitude, variability, and time course of the dynamic molecular
and cellular level neural tissue responses induced by state-of-the-art
implantable devices. Studies show that insertion injuries and foreign
body response can impact signal quality across all implanted central
nervous system (CNS) sensors to varying degrees over both acute (seconds
to minutes) and chronic periods (weeks to months). Understanding the
underlying biological processes behind the brain tissue response to
the devices at the cellular and molecular level leads to a variety
of intervention strategies for improving signal sensitivity and longevity.
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Affiliation(s)
- Takashi D. Y. Kozai
- Department
of Bioengineering, ‡Center for the Neural Basis of Cognition, §McGowan Institute
for Regenerative Medicine, ∥Department of Chemistry, and ⊥Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Andrea S. Jaquins-Gerstl
- Department
of Bioengineering, ‡Center for the Neural Basis of Cognition, §McGowan Institute
for Regenerative Medicine, ∥Department of Chemistry, and ⊥Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Alberto L. Vazquez
- Department
of Bioengineering, ‡Center for the Neural Basis of Cognition, §McGowan Institute
for Regenerative Medicine, ∥Department of Chemistry, and ⊥Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Adrian C. Michael
- Department
of Bioengineering, ‡Center for the Neural Basis of Cognition, §McGowan Institute
for Regenerative Medicine, ∥Department of Chemistry, and ⊥Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - X. Tracy Cui
- Department
of Bioengineering, ‡Center for the Neural Basis of Cognition, §McGowan Institute
for Regenerative Medicine, ∥Department of Chemistry, and ⊥Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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128
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Kozai TDY, Vazquez AL. Photoelectric artefact from optogenetics and imaging on microelectrodes and bioelectronics: New Challenges and Opportunities. J Mater Chem B 2015; 3:4965-4978. [PMID: 26167283 DOI: 10.1039/c5tb00108k] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Bioelectronics, electronic technologies that interface with biological systems, are experiencing rapid growth in terms of technology development and applications, especially in neuroscience and neuroprosthetic research. The parallel growth with optogenetics and in vivo multi-photon microscopy has also begun to generate great enthusiasm for simultaneous applications with bioelectronic technologies. However, emerging research showing artefact contaminated data highlight the need for understanding the fundamental physical principles that critically impact experimental results and complicate their interpretation. This review covers four major topics: 1) material dependent properties of the photoelectric effect (conductor, semiconductor, organic, photoelectric work function (band gap)); 2) optic dependent properties of the photoelectric effect (single photon, multiphoton, entangled biphoton, intensity, wavelength, coherence); 3) strategies and limitations for avoiding/minimizing photoelectric effects; and 4) advantages of and applications for light-based bioelectronics (photo-bioelectronics).
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Affiliation(s)
- Takashi D Y Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA. ; McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. ; Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Alberto L Vazquez
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA. ; McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA. ; Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA 15260, USA. ; Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15260, USA
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129
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Jorfi M, Skousen JL, Weder C, Capadona JR. Progress towards biocompatible intracortical microelectrodes for neural interfacing applications. J Neural Eng 2014; 12:011001. [PMID: 25460808 DOI: 10.1088/1741-2560/12/1/011001] [Citation(s) in RCA: 218] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To ensure long-term consistent neural recordings, next-generation intracortical microelectrodes are being developed with an increased emphasis on reducing the neuro-inflammatory response. The increased emphasis stems from the improved understanding of the multifaceted role that inflammation may play in disrupting both biologic and abiologic components of the overall neural interface circuit. To combat neuro-inflammation and improve recording quality, the field is actively progressing from traditional inorganic materials towards approaches that either minimizes the microelectrode footprint or that incorporate compliant materials, bioactive molecules, conducting polymers or nanomaterials. However, the immune-privileged cortical tissue introduces an added complexity compared to other biomedical applications that remains to be fully understood. This review provides a comprehensive reflection on the current understanding of the key failure modes that may impact intracortical microelectrode performance. In addition, a detailed overview of the current status of various materials-based approaches that have gained interest for neural interfacing applications is presented, and key challenges that remain to be overcome are discussed. Finally, we present our vision on the future directions of materials-based treatments to improve intracortical microelectrodes for neural interfacing.
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Affiliation(s)
- Mehdi Jorfi
- Adolphe Merkle Institute, University of Fribourg, Rte de l'Ancienne Papeterie, CH-1723 Marly, Switzerland
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130
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Sommakia S, Lee HC, Gaire J, Otto KJ. Materials approaches for modulating neural tissue responses to implanted microelectrodes through mechanical and biochemical means. CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE 2014; 18:319-328. [PMID: 25530703 PMCID: PMC4267064 DOI: 10.1016/j.cossms.2014.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Implantable intracortical microelectrodes face an uphill struggle for widespread clinical use. Their potential for treating a wide range of traumatic and degenerative neural disease is hampered by their unreliability in chronic settings. A major factor in this decline in chronic performance is a reactive response of brain tissue, which aims to isolate the implanted device from the rest of the healthy tissue. In this review we present a discussion of materials approaches aimed at modulating the reactive tissue response through mechanical and biochemical means. Benefits and challenges associated with these approaches are analyzed, and the importance of multimodal solutions tested in emerging animal models are presented.
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Affiliation(s)
- Salah Sommakia
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
| | - Heui C. Lee
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
| | - Janak Gaire
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1791
| | - Kevin J. Otto
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-1791
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1791
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131
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Kozai TD, Gugel Z, Li X, Gilgunn PJ, Khilwani R, Ozdoganlar OB, Fedder GK, Weber DJ, Cui XT. Chronic tissue response to carboxymethyl cellulose based dissolvable insertion needle for ultra-small neural probes. Biomaterials 2014; 35:9255-68. [DOI: 10.1016/j.biomaterials.2014.07.039] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 07/21/2014] [Indexed: 12/16/2022]
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132
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Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording. Biomaterials 2014; 37:25-39. [PMID: 25453935 DOI: 10.1016/j.biomaterials.2014.10.040] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 10/02/2014] [Indexed: 12/20/2022]
Abstract
Penetrating intracortical electrode arrays that record brain activity longitudinally are powerful tools for basic neuroscience research and emerging clinical applications. However, regardless of the technology used, signals recorded by these electrodes degrade over time. The failure mechanisms of these electrodes are understood to be a complex combination of the biological reactive tissue response and material failure of the device over time. While mechanical mismatch between the brain tissue and implanted neural electrodes have been studied as a source of chronic inflammation and performance degradation, the electrode failure caused by mechanical mismatch between different material properties and different structural components within a device have remained poorly characterized. Using Finite Element Model (FEM) we simulate the mechanical strain on a planar silicon electrode. The results presented here demonstrate that mechanical mismatch between iridium and silicon leads to concentrated strain along the border of the two materials. This strain is further focused on small protrusions such as the electrical traces in planar silicon electrodes. These findings are confirmed with chronic in vivo data (133-189 days) in mice by correlating a combination of single-unit electrophysiology, evoked multi-unit recordings, electrochemical impedance spectroscopy, and scanning electron microscopy from traces and electrode sites with our modeling data. Several modes of mechanical failure of chronically implanted planar silicon electrodes are found that result in degradation and/or loss of recording. These findings highlight the importance of strains and material properties of various subcomponents within an electrode array.
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133
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Gabran SRI, Salam MT, Dian J, El-Hayek Y, Perez Velazquez JL, Genov R, Carlen PL, Salama MMA, Mansour RR. 3-D Flexible Nano-Textured High-Density Microelectrode Arrays for High-Performance Neuro-Monitoring and Neuro-Stimulation. IEEE Trans Neural Syst Rehabil Eng 2014; 22:1072-82. [DOI: 10.1109/tnsre.2014.2322077] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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134
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Kozai TDY, Li X, Bodily LM, Caparosa EM, Zenonos GA, Carlisle DL, Friedlander RM, Cui XT. Effects of caspase-1 knockout on chronic neural recording quality and longevity: insight into cellular and molecular mechanisms of the reactive tissue response. Biomaterials 2014; 35:9620-34. [PMID: 25176060 DOI: 10.1016/j.biomaterials.2014.08.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 08/01/2014] [Indexed: 12/17/2022]
Abstract
Chronic implantation of microelectrodes into the cortex has been shown to lead to inflammatory gliosis and neuronal loss in the microenvironment immediately surrounding the probe, a hypothesized cause of neural recording failure. Caspase-1 (aka Interleukin 1β converting enzyme) is known to play a key role in both inflammation and programmed cell death, particularly in stroke and neurodegenerative diseases. Caspase-1 knockout (KO) mice are resistant to apoptosis and these mice have preserved neurologic function by reducing ischemia-induced brain injury in stroke models. Local ischemic injury can occur following neural probe insertion and thus in this study we investigated the hypothesis that caspase-1 KO mice would have less ischemic injury surrounding the neural probe. In this study, caspase-1 KO mice were implanted with chronic single shank 3 mm Michigan probes into V1m cortex. Electrophysiology recording showed significantly improved single-unit recording performance (yield and signal to noise ratio) of caspase-1 KO mice compared to wild type C57B6 (WT) mice over the course of up to 6 months for the majority of the depth. The higher yield is supported by the improved neuronal survival in the caspase-1 KO mice. Impedance fluctuates over time but appears to be steadier in the caspase-1 KO especially at longer time points, suggesting milder glia scarring. These findings show that caspase-1 is a promising target for pharmacologic interventions.
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Affiliation(s)
- Takashi D Y Kozai
- Bioengineering, University of Pittsburgh, USA; Center for Neural Basis of Cognition, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, USA.
| | - Xia Li
- Bioengineering, University of Pittsburgh, USA
| | - Lance M Bodily
- Neuroapoptosis Laboratory, Department of Neurological Surgery, University of Pittsburgh, USA
| | - Ellen M Caparosa
- Neuroapoptosis Laboratory, Department of Neurological Surgery, University of Pittsburgh, USA
| | - Georgios A Zenonos
- Neuroapoptosis Laboratory, Department of Neurological Surgery, University of Pittsburgh, USA
| | - Diane L Carlisle
- Neuroapoptosis Laboratory, Department of Neurological Surgery, University of Pittsburgh, USA
| | - Robert M Friedlander
- Neuroapoptosis Laboratory, Department of Neurological Surgery, University of Pittsburgh, USA
| | - X Tracy Cui
- Bioengineering, University of Pittsburgh, USA; Center for Neural Basis of Cognition, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, USA.
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135
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Kang M, Jung S, Zhang H, Kang T, Kang H, Yoo Y, Hong JP, Ahn JP, Kwak J, Jeon D, Kotov NA, Kim B. Subcellular neural probes from single-crystal gold nanowires. ACS NANO 2014; 8:8182-9. [PMID: 25112683 PMCID: PMC4535705 DOI: 10.1021/nn5024522] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/25/2014] [Indexed: 05/19/2023]
Abstract
Size reduction of neural electrodes is essential for improving the functionality of neuroprosthetic devices, developing potent therapies for neurological and neurodegenerative diseases, and long-term brain–computer interfaces. Typical neural electrodes are micromanufactured devices with dimensions ranging from tens to hundreds of micrometers. Their further miniaturization is necessary to reduce local tissue damage and chronic immunological reactions of the brain. Here we report the neural electrode with subcellular dimensions based on single-crystalline gold nanowires (NWs) with a diameter of ∼100 nm. Unique mechanical and electrical properties of defect-free gold NWs enabled their implantation and recording of single neuron-activities in a live mouse brain despite a ∼50× reduction of the size compared to the closest analogues. Reduction of electrode dimensions enabled recording of neural activity with improved spatial resolution and differentiation of brain activity in response to different social situations for mice. The successful localization of the epileptic seizure center was also achieved using a multielectrode probe as a demonstration of the diagnostics potential of NW electrodes. This study demonstrated the realism of single-neuron recording using subcellular-sized electrodes that may be considered a pivotal point for use in diverse studies of chronic brain diseases.
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Affiliation(s)
- Mijeong Kang
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
| | - Seungmoon Jung
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
| | - Huanan Zhang
- Department of Chemical Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Taejoon Kang
- BioNanotechnology Research Center and BioNano Health Guard Research Center, KRIBB, Daejeon 305-806, Korea
| | - Hosuk Kang
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
| | - Youngdong Yoo
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
| | - Jin-Pyo Hong
- Department of Psychiatry, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea
| | | | - Juhyoun Kwak
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
| | - Daejong Jeon
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
- Address correspondence to (D. Jeon); (N. A. Kotov); (B. Kim)
| | - Nicholas A. Kotov
- Department of Chemical Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Address correspondence to (D. Jeon); (N. A. Kotov); (B. Kim)
| | - Bongsoo Kim
- Department of Chemistry and Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea
- Address correspondence to (D. Jeon); (N. A. Kotov); (B. Kim)
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136
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Nguyen JK, Park DJ, Skousen JL, Hess-Dunning AE, Tyler DJ, Rowan SJ, Weder C, Capadona JR. Mechanically-compliant intracortical implants reduce the neuroinflammatory response. J Neural Eng 2014; 11:056014. [PMID: 25125443 DOI: 10.1088/1741-2560/11/5/056014] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE The mechanisms underlying intracortical microelectrode encapsulation and failure are not well understood. A leading hypothesis implicates the role of the mechanical mismatch between rigid implant materials and the much softer brain tissue. Previous work has established the benefits of compliant materials on reducing early neuroinflammatory events. However, recent studies established late onset of a disease-like neurodegenerative state. APPROACH In this study, we implanted mechanically-adaptive materials, which are initially rigid but become compliant after implantation, to investigate the long-term chronic neuroinflammatory response to compliant intracortical microelectrodes. MAIN RESULTS Three days after implantation, during the acute healing phase of the response, the tissue response to the compliant implants was statistically similar to that of chemically matched stiff implants with much higher rigidity. However, at two, eight, and sixteen weeks post-implantation in the rat cortex, the compliant implants demonstrated a significantly reduced neuroinflammatory response when compared to stiff reference materials. Chronically implanted compliant materials also exhibited a more stable blood-brain barrier than the stiff reference materials. SIGNIFICANCE Overall, the data show strikingly that mechanically-compliant intracortical implants can reduce the neuroinflammatory response in comparison to stiffer systems.
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Affiliation(s)
- Jessica K Nguyen
- Department of Biomedical Engineering, Case Western Reserve University, 2071 Martin Luther King Jr Drive, Wickenden Bldg, Cleveland, OH 44106, USA. Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd, 151W/APT, Cleveland, OH 44106-1702, USA
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137
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Reeder J, Kaltenbrunner M, Ware T, Arreaga-Salas D, Avendano-Bolivar A, Yokota T, Inoue Y, Sekino M, Voit W, Sekitani T, Someya T. Mechanically adaptive organic transistors for implantable electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:4967-4973. [PMID: 24733490 DOI: 10.1002/adma.201400420] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 02/19/2014] [Indexed: 06/03/2023]
Abstract
A unique form of adaptive electronics is demonstrated, which change their mechanical properties from rigid and planar to soft and compliant, in order to enable soft and conformal wrapping around 3D objects, including biological tissue. These devices feature excellent mechanical robustness and maintain initial electrical properties even after changing shape and stiffness.
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Affiliation(s)
- Jonathan Reeder
- Electrical and Electronic Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan; Department of Materials Science and Engineering, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, Texas, 75080-3021, USA
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138
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Large enhancement in neurite outgrowth on a cell membrane-mimicking conducting polymer. Nat Commun 2014; 5:4523. [DOI: 10.1038/ncomms5523] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 06/25/2014] [Indexed: 01/24/2023] Open
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139
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A comparison of polymer substrates for photolithographic processing of flexible bioelectronics. Biomed Microdevices 2014; 15:925-39. [PMID: 23852172 DOI: 10.1007/s10544-013-9782-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Flexible bioelectronics encompass a new generation of sensing devices, in which controlled interactions with tissue enhance understanding of biological processes in vivo. However, the fabrication of such thin film electronics with photolithographic processes remains a challenge for many biocompatible polymers. Recently, two shape memory polymer (SMP) systems, based on acrylate and thiol-ene/acrylate networks, were designed as substrates for softening neural interfaces with glass transitions above body temperature (37 °C) such that the materials are stiff for insertion into soft tissue and soften through low moisture absorption in physiological conditions. These two substrates, acrylate and thiol-ene/acrylate SMPs, are compared to polyethylene naphthalate, polycarbonate, polyimide, and polydimethylsiloxane, which have been widely used in flexible electronics research and industry. These six substrates are compared via dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and swelling studies. The integrity of gold and chromium/gold thin films on SMP substrates are evaluated with optical profilometry and electrical measurements as a function of processing temperature above, below and through the glass transition temperature. The effects of crosslink density, adhesion and cure stress are shown to play a critical role in the stability of these thin film materials, and a guide for the future design of responsive polymeric materials suitable for neural interfaces is proposed. Finally, neural interfaces fabricated on thiol-ene/acrylate substrates demonstrate long-term fidelity through both in vitro impedance spectroscopy and the recording of driven local field potentials for 8 weeks in the auditory cortex of laboratory rats.
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140
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Sohal HS, Jackson A, Jackson R, Clowry GJ, Vassilevski K, O'Neill A, Baker SN. The sinusoidal probe: a new approach to improve electrode longevity. FRONTIERS IN NEUROENGINEERING 2014; 7:10. [PMID: 24808859 PMCID: PMC4010751 DOI: 10.3389/fneng.2014.00010] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 04/07/2014] [Indexed: 11/13/2022]
Abstract
Micromotion between the brain and implanted electrodes is a major contributor to the failure of invasive brain-machine interfaces. Movements of the electrode tip cause recording instabilities while spike amplitudes decline over the weeks/months post-implantation due to glial cell activation caused by sustained mechanical trauma. We have designed a sinusoidal probe in order to reduce movement of the recording tip relative to the surrounding neural tissue. The probe was microfabricated from flexible materials and incorporated a sinusoidal shaft to minimize tethering forces and a 3D spheroid tip to anchor the recording site within the brain. Compared to standard microwire electrodes, the signal-to-noise ratio and local field potential power of sinusoidal probe recordings from rabbits was more stable across recording periods up to 678 days. Histological quantification of microglia and astrocytes showed reduced neuronal tissue damage especially for the tip region between 6 and 24 months post-implantation. We suggest that the micromotion-reducing measures incorporated into our design, at least partially, decreased the magnitude of gliosis, resulting in enhanced longevity of recording.
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Affiliation(s)
- Harbaljit S Sohal
- Newcastle Movement Lab, Institute of Neuroscience, Newcastle University Newcastle Upon Tyne, UK ; School of Electrical and Electronic Engineering, Newcastle University Newcastle Upon Tyne, UK
| | - Andrew Jackson
- Newcastle Movement Lab, Institute of Neuroscience, Newcastle University Newcastle Upon Tyne, UK
| | - Richard Jackson
- School of Electrical and Electronic Engineering, Newcastle University Newcastle Upon Tyne, UK
| | - Gavin J Clowry
- Newcastle Movement Lab, Institute of Neuroscience, Newcastle University Newcastle Upon Tyne, UK
| | - Konstantin Vassilevski
- School of Electrical and Electronic Engineering, Newcastle University Newcastle Upon Tyne, UK
| | - Anthony O'Neill
- School of Electrical and Electronic Engineering, Newcastle University Newcastle Upon Tyne, UK
| | - Stuart N Baker
- Newcastle Movement Lab, Institute of Neuroscience, Newcastle University Newcastle Upon Tyne, UK
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141
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Ware T, Jennings AR, Bassampour ZS, Simon D, Son DY, Voit W. Degradable, silyl ether thiol–ene networks. RSC Adv 2014. [DOI: 10.1039/c4ra06997h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The polymerization of silyl ether containing thiols and alkenes results in tunable, degradable thermosets with potential in implantable electronics.
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Affiliation(s)
- Taylor Ware
- Department of Materials Science and Engineering
- The University of Texas at Dallas
- Richardson, USA
| | - Abby R. Jennings
- Department of Chemistry
- Center for Drug Discovery
- Design, and Delivery (CD4)
- Southern Methodist University
- Dallas, USA
| | - Zahra S. Bassampour
- Department of Chemistry
- Center for Drug Discovery
- Design, and Delivery (CD4)
- Southern Methodist University
- Dallas, USA
| | - Dustin Simon
- Department of Materials Science and Engineering
- The University of Texas at Dallas
- Richardson, USA
| | - David Y. Son
- Department of Chemistry
- Center for Drug Discovery
- Design, and Delivery (CD4)
- Southern Methodist University
- Dallas, USA
| | - Walter Voit
- Department of Materials Science and Engineering
- The University of Texas at Dallas
- Richardson, USA
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142
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McGie SC, Nagai MK, Artinian-Shaheen T. Clinical ethical concerns in the implantation of brain-machine interfaces. IEEE Pulse 2013; 4:32-7. [PMID: 23558502 DOI: 10.1109/mpul.2013.2242014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Steven C McGie
- The Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario, Canada.
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143
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Ware T, Simon D, Hearon K, Kang TH, Maitland DJ, Voit W. Thiol-click chemistries for responsive neural interfaces. Macromol Biosci 2013; 13:1640-7. [PMID: 24115484 PMCID: PMC4817906 DOI: 10.1002/mabi.201300272] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/22/2013] [Indexed: 11/11/2022]
Abstract
Neural interfaces provide an electrical connection between computers and the nervous system: current penetrating devices are orders-of-magnitude stiffer than surrounding tissue. In this work, recent efforts in softening electronics and utilize thiol-ene and thiol-epoxy "click" reactions are built upon to incorporate fluid-sensitive hydrogen bonding into smart substrates for high electrode density neural interfaces. The modulus of these substrates drops more than two orders of magnitude in response to physiological conditions, despite fluid uptake of less than 6%, and can be tuned by the covalent crosslink density and degree of hydrogen bonding in the polymer network. Intracortical and intrafascicular electrode arrays are fabricated and characterized with impedance spectroscopy and cyclic voltammetry.
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Affiliation(s)
- Taylor Ware
- Department of Materials Science and Engineering, The University of Texas at Dallas, 800 West Campbell Rd, Mailstop RL 3, Richardson, TX, 75080, USA
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144
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Sridharan A, Rajan SD, Muthuswamy J. Long-term changes in the material properties of brain tissue at the implant-tissue interface. J Neural Eng 2013; 10:066001. [PMID: 24099854 DOI: 10.1088/1741-2560/10/6/066001] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE Brain tissue undergoes dramatic molecular and cellular remodeling at the implant-tissue interface that evolves over a period of weeks after implantation. The biomechanical impact of such remodeling on the interface remains unknown. In this study, we aim to assess the changes in the mechanical properties of the brain-electrode interface after chronic implantation of a microelectrode. APPROACH Microelectrodes were implanted in the rodent cortex at a depth of 1 mm for different durations-1 day (n = 4), 10-14 days (n = 4), 4 weeks (n = 4) and 6-8 weeks (n = 7). After the initial duration of implantation, the microelectrodes were moved an additional 1 mm downward at a constant speed of 10 µm s(-1). Forces experienced by the microelectrode were measured during movement and after termination of movement. The biomechanical properties of the interfacial brain tissue were assessed from measured force-displacement curves using two separate models-a two-parameter Mooney-Rivlin hyperelastic model and a viscoelastic model with a second-order Prony series. MAIN RESULTS Estimated shear moduli using a second-order viscoelastic model increased from 0.5-2.6 kPa (day 1 of implantation) to 25.7-59.3 kPa (after 4 weeks of implantation) and subsequently decreased to 0.8-7.9 kPa after 6-8 weeks of implantation in 6 of the 7 animals. The estimated elastic modulus increased from 4.1-7.8 kPa on the day of implantation to 24-44.9 kPa after 4 weeks. The elastic modulus was estimated to be 6.8-33.3 kPa in 6 of the 7 animals after 6-8 weeks of implantation. The above estimates suggest that the brain tissue surrounding the microelectrode evolves from a stiff matrix with maximal shear and elastic modulus after 4 weeks of implantation into a composite of two different layers with different mechanical properties-a stiff compact inner layer surrounded by softer brain tissue that is biomechanically similar to brain tissue-during the first week of implantation. Tissue micromotion-induced stresses on the microelectrode constituted 12-55% of the steady-state stresses on the microelectrode on the day of implantation (n = 4), 2-21% of the steady-state stresses after 4 weeks of implantation (n = 4), and 4-10% of the steady-state stresses after 6-8 weeks of implantation (n = 7). SIGNIFICANCE Understanding biomechanical behavior at the brain-microelectrode interface is necessary for the long-term success of implantable neuroprosthetics and microelectrode arrays. Such quantitative physical characterization of the dynamic changes in the electrode-tissue interface will (a) drive the design and development of more mechanically optimal, chronic brain implants, and (b) lead to new insights into key cellular and molecular events such as neuronal adhesion, migration and function in the immediate vicinity of the brain implant.
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Affiliation(s)
- Arati Sridharan
- School of Biological & Health Systems Engineering, Ira A Fulton School of Engineering, Arizona State University, Tempe, AZ 85287, USA
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145
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Felix SH, Shah KG, Tolosa VM, Sheth HJ, Tooker AC, Delima TL, Jadhav SP, Frank LM, Pannu SS. Insertion of flexible neural probes using rigid stiffeners attached with biodissolvable adhesive. J Vis Exp 2013:e50609. [PMID: 24121443 DOI: 10.3791/50609] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Microelectrode arrays for neural interface devices that are made of biocompatible thin-film polymer are expected to have extended functional lifetime because the flexible material may minimize adverse tissue response caused by micromotion. However, their flexibility prevents them from being accurately inserted into neural tissue. This article demonstrates a method to temporarily attach a flexible microelectrode probe to a rigid stiffener using biodissolvable polyethylene glycol (PEG) to facilitate precise, surgical insertion of the probe. A unique stiffener design allows for uniform distribution of the PEG adhesive along the length of the probe. Flip-chip bonding, a common tool used in microelectronics packaging, enables accurate and repeatable alignment and attachment of the probe to the stiffener. The probe and stiffener are surgically implanted together, then the PEG is allowed to dissolve so that the stiffener can be extracted leaving the probe in place. Finally, an in vitro test method is used to evaluate stiffener extraction in an agarose gel model of brain tissue. This approach to implantation has proven particularly advantageous for longer flexible probes (>3 mm). It also provides a feasible method to implant dual-sided flexible probes. To date, the technique has been used to obtain various in vivo recording data from the rat cortex.
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Affiliation(s)
- Sarah H Felix
- Materials Engineering Division, Lawrence Livermore National Laboratory
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146
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Zhang H, Patel PR, Xie Z, Swanson SD, Wang X, Kotov NA. Tissue-compliant neural implants from microfabricated carbon nanotube multilayer composite. ACS NANO 2013; 7:7619-7629. [PMID: 23930825 DOI: 10.1021/nn402074y] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Current neural prosthetic devices (NPDs) induce chronic inflammation due to complex mechanical and biological reactions related, in part, to staggering discrepancies of mechanical properties with neural tissue. Relatively large size of the implants and traumas to blood-brain barrier contribute to inflammation reactions, as well. Mitigation of these problems and the realization of long-term brain interface require a new generation of NPDs fabricated from flexible materials compliant with the brain tissue. However, such materials will need to display hard-to-combine mechanical and electrical properties which are not available in the toolbox of classical neurotechnology. Moreover, these new materials will concomitantly demand different methods of (a) device micromanufacturing and (b) surgical implantation in brains because currently used processes take advantage of high stiffness of the devices. Carbon nanotubes (CNTs) serve as a promising foundation for such materials because of their record mechanical and electrical properties, but CNT-based tissue-compliant devices have not been realized yet. In this study, we formalize the mechanical requirements to tissue-compliant implants based on critical rupture strength of brain tissue and demonstrate that miniature CNT-based devices can satisfy these requirements. We fabricated them using MEMS-like technology and miniaturized them so that at least two dimensions of the electrodes would be comparable to brain tissue cells. The nanocomposite-based flexible neural electrodes were implanted into the rat motor cortex using a surgical procedure specifically designed for soft tissue-compliant implants. The post-surgery implant localization in the motor cortex was successfully visualized with magnetic resonance and photoacoustic imaging. In vivo functionality was demonstrated by successful registration of the low-frequency neural recording in the live brain of anesthetized rats. Investigation of inflammation processes around these electrodes will be required to establish their prospects as long-term neural electrodes.
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Affiliation(s)
- Huanan Zhang
- Department of Chemical Engineering, ‡Department of Biomedical Engineering, §Department of Radiology, ⊥Department of Materials Science, and ∥Biointerface Institute, University of Michigan , Ann Arbor, Michigan 48109, United States
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147
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Sankar V, Sanchez JC, McCumiskey E, Brown N, Taylor CR, Ehlert GJ, Sodano HA, Nishida T. A highly compliant serpentine shaped polyimide interconnect for front-end strain relief in chronic neural implants. Front Neurol 2013; 4:124. [PMID: 24062716 PMCID: PMC3770980 DOI: 10.3389/fneur.2013.00124] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 08/19/2013] [Indexed: 11/13/2022] Open
Abstract
While the signal quality of recording neural electrodes is observed to degrade over time, the degradation mechanisms are complex and less easily observable. Recording microelectrodes failures are attributed to different biological factors such as tissue encapsulation, immune response, and disruption of blood-brain barrier (BBB) and non-biological factors such as strain due to micromotion, insulation delamination, corrosion, and surface roughness on the recording site (1–4). Strain due to brain micromotion is considered to be one of the important abiotic factors contributing to the failure of the neural implants. To reduce the forces exerted by the electrode on the brain, a high compliance 2D serpentine shaped electrode cable was designed, simulated, and measured using polyimide as the substrate material. Serpentine electrode cables were fabricated using MEMS microfabrication techniques, and the prototypes were subjected to load tests to experimentally measure the compliance. The compliance of the serpentine cable was numerically modeled and quantitatively measured to be up to 10 times higher than the compliance of a straight cable of same dimensions and material.
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Affiliation(s)
- Viswanath Sankar
- Department of Electrical and Computer Engineering, University of Florida , Gainesville, FL , USA
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148
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Guitchounts G, Markowitz JE, Liberti WA, Gardner TJ. A carbon-fiber electrode array for long-term neural recording. J Neural Eng 2013; 10:046016. [PMID: 23860226 DOI: 10.1088/1741-2560/10/4/046016] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Chronic neural recording in behaving animals is an essential method for studies of neural circuit function. However, stable recordings from small, densely packed neurons remains challenging, particularly over time-scales relevant for learning. APPROACH We describe an assembly method for a 16-channel electrode array consisting of carbon fibers (<5 µm diameter) individually insulated with Parylene-C and fire-sharpened. The diameter of the array is approximately 26 µm along the full extent of the implant. MAIN RESULTS Carbon fiber arrays were tested in HVC (used as a proper name), a song motor nucleus, of singing zebra finches where individual neurons discharge with temporally precise patterns. Previous reports of activity in this population of neurons have required the use of high impedance electrodes on movable microdrives. Here, the carbon fiber electrodes provided stable multi-unit recordings over time-scales of months. Spike-sorting indicated that the multi-unit signals were dominated by one, or a small number of cells. Stable firing patterns during singing confirmed the stability of these clusters over time-scales of months. In addition, from a total of 10 surgeries, 16 projection neurons were found. This cell type is characterized by sparse stereotyped firing patterns, providing unambiguous confirmation of single cell recordings. SIGNIFICANCE Carbon fiber electrode bundles may provide a scalable solution for long-term neural recordings of densely packed neurons.
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Affiliation(s)
- Grigori Guitchounts
- Department of Biology, Boston University, 24 Cummington Mall, Boston, MA 02215, USA
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149
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Gutowski SM, Templeman KL, South AB, Gaulding JC, Shoemaker JT, LaPlaca MC, Bellamkonda RV, Lyon LA, García AJ. Host response to microgel coatings on neural electrodes implanted in the brain. J Biomed Mater Res A 2013; 102:1486-99. [PMID: 23666919 DOI: 10.1002/jbm.a.34799] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 04/15/2013] [Accepted: 05/03/2013] [Indexed: 11/10/2022]
Abstract
The performance of neural electrodes implanted in the brain is often limited by host response in the surrounding brain tissue, including astrocytic scar formation, neuronal cell death, and inflammation around the implant. We applied conformal microgel coatings to silicon neural electrodes and examined host responses to microgel-coated and uncoated electrodes following implantation in the rat brain. In vitro analyses demonstrated significantly reduced astrocyte and microglia adhesion to microgel-coated electrodes compared to uncoated controls. Microgel-coated and uncoated electrodes were implanted in the rat brain cortex and the extent of activated microglia and astrocytes as well as neuron density around the implant were evaluated at 1, 4, and 24 weeks postimplantation. Microgel coatings reduced astrocytic recruitment around the implant at later time points. However, microglial response indicated persistence of inflammation in the area around the electrode. Neuronal density around the implanted electrodes was also lower for both implant groups compared to the uninjured control. These results demonstrate that microgel coatings do not significantly improve host responses to implanted neural electrodes and underscore the need for further improvements in implantable materials.
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Affiliation(s)
- Stacie M Gutowski
- Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, 30332-0363; Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332-0363
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150
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Avendano-Bolivar A, Ware T, Arreaga-Salas D, Simon D, Voit W. Mechanical cycling stability of organic thin film transistors on shape memory polymers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:3095-3099. [PMID: 23703745 DOI: 10.1002/adma.201203976] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Revised: 01/16/2013] [Indexed: 06/02/2023]
Abstract
Organic thin film transistors on shape memory polymers are fabricated by full photolithography. Devices show high mobility (0.2 cm(2) V(-1) s(-1)) and close to zero threshold voltage (-4.5 V) when characterized as fabricated. After 1, 10, and 100 deformation cycles and in a deformed, metastable shape memory transition state, changes in mobility and V(th) are measured and indicate sustained device functionality.
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Affiliation(s)
- Adrian Avendano-Bolivar
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA
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