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Chen FD, Sharma A, Roszko DA, Xue T, Mu X, Luo X, Chua H, Lo PGQ, Sacher WD, Poon JKS. Development of wafer-scale multifunctional nanophotonic neural probes for brain activity mapping. LAB ON A CHIP 2024; 24:2397-2417. [PMID: 38623840 DOI: 10.1039/d3lc00931a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Optical techniques, such as optogenetic stimulation and functional fluorescence imaging, have been revolutionary for neuroscience by enabling neural circuit analysis with cell-type specificity. To probe deep brain regions, implantable light sources are crucial. Silicon photonics, commonly used for data communications, shows great promise in creating implantable devices with complex optical systems in a compact form factor compatible with high volume manufacturing practices. This article reviews recent developments of wafer-scale multifunctional nanophotonic neural probes. The probes can be realized on 200 or 300 mm wafers in commercial foundries and integrate light emitters for photostimulation, microelectrodes for electrophysiological recording, and microfluidic channels for chemical delivery and sampling. By integrating active optical devices to the probes, denser emitter arrays, enhanced on-chip biosensing, and increased ease of use may be realized. Silicon photonics technology makes possible highly versatile implantable neural probes that can transform neuroscience experiments.
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Affiliation(s)
- Fu Der Chen
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Ankita Sharma
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - David A Roszko
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Tianyuan Xue
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Xin Mu
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Xianshu Luo
- Advanced Micro Foundry Pte Ltd, 11 Science Park Road, Singapore Science Park II, 117685, Singapore
| | - Hongyao Chua
- Advanced Micro Foundry Pte Ltd, 11 Science Park Road, Singapore Science Park II, 117685, Singapore
| | - Patrick Guo-Qiang Lo
- Advanced Micro Foundry Pte Ltd, 11 Science Park Road, Singapore Science Park II, 117685, Singapore
| | - Wesley D Sacher
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
| | - Joyce K S Poon
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
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2
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Wells SS, Bain IJ, Valenta AC, Lenhart AE, Steyer DJ, Kennedy RT. Microdialysis coupled with droplet microfluidics and mass spectrometry for determination of neurotransmitters in vivo with high temporal resolution. Analyst 2024; 149:2328-2337. [PMID: 38488040 PMCID: PMC11018092 DOI: 10.1039/d4an00112e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 03/10/2024] [Indexed: 04/16/2024]
Abstract
Monitoring the concentration fluctuations of neurotransmitters in vivo is valuable for elucidating the chemical signals that underlie brain functions. Microdialysis sampling is a widely used tool for monitoring neurochemicals in vivo. The volume requirements of most techniques that have been coupled to microdialysis, such as HPLC, result in fraction collection times of minutes, thus limiting the temporal resolution possible. Further the time of analysis can become long for cases where many fractions are collected. Previously we have used direct analysis of dialysate by low-flow electrospray ionization-tandem mass spectrometry (ESI-MS/MS) on a triple quadrupole mass spectrometer to monitor acetylcholine, glutamate, and γ-amino-butyric acid to achieve multiplexed in vivo monitoring with temporal resolution of seconds. Here, we have expanded this approach to adenosine, dopamine, and serotonin. The method achieved limits of detection down to 2 nM, enabling basal concentrations of all these compounds, except serotonin, to be measured in vivo. Comparative analysis with LC-MS/MS showed accurate results for all compounds except for glutamate, possibly due to interference for this compound in vivo. Pairing this analysis with droplet microfluidics yields 11 s temporal resolution and can generate dialysate fractions down to 3 nL at rates up to 3 fractions per s from a microdialysis probe. The system is applied to multiplexed monitoring of neurotransmitter dynamics in response to stimulation by 100 mM K+ and amphetamine. These applications demonstrate the suitability of the droplet ESI-MS/MS method for monitoring short-term dynamics of up to six neurotransmitters simultaneously.
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Affiliation(s)
- Shane S Wells
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
| | - Ian J Bain
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
| | - Alec C Valenta
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
| | - Ashley E Lenhart
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
| | - Daniel J Steyer
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
| | - Robert T Kennedy
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109-1055, USA.
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Park I, Kim S, Brenden CK, Shi W, Iyer H, Bashir R, Vlasov Y. Highly Localized Chemical Sampling at Subsecond Temporal Resolution Enabled with a Silicon Nanodialysis Platform at Nanoliter per Minute Flows. ACS NANO 2024; 18:6963-6974. [PMID: 38378186 PMCID: PMC10919076 DOI: 10.1021/acsnano.3c09776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 02/06/2024] [Accepted: 02/08/2024] [Indexed: 02/22/2024]
Abstract
Microdialysis (MD) is a versatile and powerful technique for chemical profiling of biological tissues and is widely used for quantification of neurotransmitters, neuropeptides, metabolites, biomarkers, and drugs in the central nervous system as well as in dermatology, ophthalmology, and pain research. However, MD performance is severely limited by fundamental tradeoffs between chemical sensitivity, spatial resolution, and temporal response. Here, by using wafer-scale silicon microfabrication, we develop and demonstrate a nanodialysis (ND) sampling probe that enables highly localized chemical sampling with 100 μm spatial resolution and subsecond temporal resolution at high recovery rates. These performance metrics, which are 100-1000× superior to existing MD approaches, are enabled by a 100× reduction of the microfluidic channel cross-section, a corresponding drastic 100× reduction of flow rates to exceedingly slow few nL/min flows, and integration of a nanometer-thin nanoporous membrane with high transport flux into the probe sampling area. Miniaturized ND probes may allow for the minimally invasive and highly localized sampling and chemical profiling in live biological tissues with high spatiotemporal resolution for clinical, biomedical, and pharmaceutical applications.
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Affiliation(s)
| | | | | | - Weihua Shi
- University of Illinois at
Urbana−Champaign, Urbana, Illinois 61820, United States
| | - Hrishikesh Iyer
- University of Illinois at
Urbana−Champaign, Urbana, Illinois 61820, United States
| | - Rashid Bashir
- University of Illinois at
Urbana−Champaign, Urbana, Illinois 61820, United States
| | - Yurii Vlasov
- University of Illinois at
Urbana−Champaign, Urbana, Illinois 61820, United States
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4
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Park I, Kim S, Brenden CK, Shi W, Iyer H, Bashir R, Vlasov Y. Highly localized chemical sampling at sub-second temporal resolution enabled with a silicon nanodialysis platform at exceedingly slow flows. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.08.556607. [PMID: 37745310 PMCID: PMC10515758 DOI: 10.1101/2023.09.08.556607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Microdialysis (MD) is a versatile and powerful technique for chemical profiling of biological tissues and is widely used for quantification of neurotransmitters, neuropeptides, metabolites, biomarkers, and drugs in the central nervous system as well as in dermatology, ophthalmology, and in pain research. However, MD performance is severely limited by fundamental tradeoffs between chemical sensitivity, spatial resolution, and temporal response. Here, by using wafer-scale silicon microfabrication, we develop and demonstrate a nanodialysis (ND) sampling probe that enables highly localized chemical sampling with 100μm spatial resolution and sub-second temporal resolution at high recovery rates. These performance metrics, which are 100X-1000X superior to existing MD approaches, are enabled by a 100X reduction of the microfluidic channel cross-section, a corresponding drastic 100X reduction of flow rates to exceedingly slow few nL/min flows, and integration of a nanometer-thin nanoporous membrane with high transport flux into the probe sampling area. Miniaturized ND probes may allow for the minimally invasive and highly localized sampling and chemical profiling in live biological tissues with unprecedented spatio-temporal resolution for clinical, biomedical, and pharmaceutical applications.
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5
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Shi W, Bell S, Iyer H, Brenden CK, Zhang Y, Kim S, Park I, Bashir R, Sweedler J, Vlasov Y. Integrated silicon microfluidic chip for picoliter-scale analyte segmentation and microscale printing for mass spectrometry imaging. LAB ON A CHIP 2022; 23:72-80. [PMID: 36477760 PMCID: PMC9764807 DOI: 10.1039/d2lc00688j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 11/12/2022] [Indexed: 06/17/2023]
Abstract
A silicon single-chip microfluidics system that integrates microscale fluidic channels, an analyte segmentation device, and a nozzle for electrohydrodynamic-assisted printing is designed for hyphenation with MALDI mass spectrometry (MS) imaging. A miniaturized T-junction segments analytes into monodisperse picoliter oil-isolated compartments. The printing nozzle deposits generated droplets one-by-one into an array on a conductive substrate without splitting or coalescing. Virtually single-shot MS analysis is enabled due to the ultrasmall droplet volumes and highly localized printing. The signal-to-noise ratio indicates that detection limits at the attomole level are achieved for γ-aminobutyric acid.
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Affiliation(s)
- Weihua Shi
- Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, IL 61801, USA.
| | - Sara Bell
- Department of Chemistry and the Beckman Institute, University of Illinois Urbana Champaign, IL 61801, USA
| | - Hrishikesh Iyer
- Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, IL 61801, USA.
| | | | - Yan Zhang
- Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, IL 61801, USA.
| | - Sungho Kim
- Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, IL 61801, USA.
| | - Insu Park
- Department of Bioengineering, University of Illinois Urbana Champaign, IL 61801, USA
| | - Rashid Bashir
- Department of Bioengineering, University of Illinois Urbana Champaign, IL 61801, USA
| | - Jonathan Sweedler
- Department of Chemistry and the Beckman Institute, University of Illinois Urbana Champaign, IL 61801, USA
| | - Yurii Vlasov
- Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, IL 61801, USA.
- Department of Bioengineering, University of Illinois Urbana Champaign, IL 61801, USA
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6
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Teixidor J, Novello S, Ortiz D, Menin L, Lashuel HA, Bertsch A, Renaud P. On-Demand Nanoliter Sampling Probe for the Collection of Brain Fluid. Anal Chem 2022; 94:10415-10426. [PMID: 35786947 DOI: 10.1021/acs.analchem.2c01577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Continuous fluidic sampling systems allow collection of brain biomarkers in vivo. Here, we propose a new sequential and intermittent sampling paradigm using droplets, called Droplet on Demand (DoD). It is implemented in a microfabricated neural probe and alternates phases of analyte removal from the tissue and phases of equilibration of the concentration in the tissue. It allows sampling droplets loaded with molecules from the brain extracellular fluid punctually, without the long transient equilibration periods typical of continuous methods. It uses an accurately defined fluidic sequence with controlled timings, volumes, and flow rates, and correct operation is verified by the embedded electrodes and a flow sensor. As a proof of concept, we demonstrated the application of this novel approach in vitro and in vivo, to collect glucose in the brain of mice, with a temporal resolution of 1-2 min and without transient regime. Absolute quantification of the glucose level in the samples was performed by direct infusion nanoelectrospray ionization Fourier transform mass spectrometry (nanoESI-FTMS). By adjusting the diffusion time and the perfusion volume of DoD, the fraction of molecules recovered in the samples can be tuned to mirror the tissue concentration at accurate points in time. Moreover, this makes quantification of biomarkers in the brain possible within acute experiments of only 20-120 min. DoD provides a complementary tool to continuous microdialysis and push-pull sampling probes. Thus, the advances allowed by DoD will benefit quantitative molecular studies in the brain, i.e., for molecules involved in volume transmission or for protein aggregates that form in neurodegenerative diseases over long periods.
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Affiliation(s)
- Joan Teixidor
- Microsystems Laboratory 4 (STI-IEM-LMIS4), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Salvatore Novello
- Laboratory of Molecular and Chemical Biology of Neurodegeneration (SV-BMI-LMNN), EPFL, 1015 Lausanne, Switzerland
| | - Daniel Ortiz
- Mass Spectrometry and Elemental Analysis Platform (SB-ISIC-MSEAP), EPFL, 1015 Lausanne, Switzerland
| | - Laure Menin
- Mass Spectrometry and Elemental Analysis Platform (SB-ISIC-MSEAP), EPFL, 1015 Lausanne, Switzerland
| | - Hilal A Lashuel
- Laboratory of Molecular and Chemical Biology of Neurodegeneration (SV-BMI-LMNN), EPFL, 1015 Lausanne, Switzerland
| | - Arnaud Bertsch
- Microsystems Laboratory 4 (STI-IEM-LMIS4), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Philippe Renaud
- Microsystems Laboratory 4 (STI-IEM-LMIS4), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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7
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Wan J, Zhou S, Mea HJ, Guo Y, Ku H, Urbina BM. Emerging Roles of Microfluidics in Brain Research: From Cerebral Fluids Manipulation to Brain-on-a-Chip and Neuroelectronic Devices Engineering. Chem Rev 2022; 122:7142-7181. [PMID: 35080375 DOI: 10.1021/acs.chemrev.1c00480] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Remarkable progress made in the past few decades in brain research enables the manipulation of neuronal activity in single neurons and neural circuits and thus allows the decipherment of relations between nervous systems and behavior. The discovery of glymphatic and lymphatic systems in the brain and the recently unveiled tight relations between the gastrointestinal (GI) tract and the central nervous system (CNS) further revolutionize our understanding of brain structures and functions. Fundamental questions about how neurons conduct two-way communications with the gut to establish the gut-brain axis (GBA) and interact with essential brain components such as glial cells and blood vessels to regulate cerebral blood flow (CBF) and cerebrospinal fluid (CSF) in health and disease, however, remain. Microfluidics with unparalleled advantages in the control of fluids at microscale has emerged recently as an effective approach to address these critical questions in brain research. The dynamics of cerebral fluids (i.e., blood and CSF) and novel in vitro brain-on-a-chip models and microfluidic-integrated multifunctional neuroelectronic devices, for example, have been investigated. This review starts with a critical discussion of the current understanding of several key topics in brain research such as neurovascular coupling (NVC), glymphatic pathway, and GBA and then interrogates a wide range of microfluidic-based approaches that have been developed or can be improved to advance our fundamental understanding of brain functions. Last, emerging technologies for structuring microfluidic devices and their implications and future directions in brain research are discussed.
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Affiliation(s)
- Jiandi Wan
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Sitong Zhou
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Hing Jii Mea
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Yaojun Guo
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, United States
| | - Hansol Ku
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, United States
| | - Brianna M Urbina
- Biochemistry, Molecular, Cellular and Developmental Biology Program, University of California, Davis, California 95616, United States
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8
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Stangler LA, Kouzani A, Bennet KE, Dumee L, Berk M, Worrell GA, Steele S, Burns TC, Howe CL. Microdialysis and microperfusion electrodes in neurologic disease monitoring. Fluids Barriers CNS 2021; 18:52. [PMID: 34852829 PMCID: PMC8638547 DOI: 10.1186/s12987-021-00292-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 11/23/2021] [Indexed: 11/10/2022] Open
Abstract
Contemporary biomarker collection techniques in blood and cerebrospinal fluid have to date offered only modest clinical insights into neurologic diseases such as epilepsy and glioma. Conversely, the collection of human electroencephalography (EEG) data has long been the standard of care in these patients, enabling individualized insights for therapy and revealing fundamental principles of human neurophysiology. Increasing interest exists in simultaneously measuring neurochemical biomarkers and electrophysiological data to enhance our understanding of human disease mechanisms. This review compares microdialysis, microperfusion, and implanted EEG probe architectures and performance parameters. Invasive consequences of probe implantation are also investigated along with the functional impact of biofouling. Finally, previously developed microdialysis electrodes and microperfusion electrodes are reviewed in preclinical and clinical settings. Critically, current and precedent microdialysis and microperfusion probes lack the ability to collect neurochemical data that is spatially and temporally coincident with EEG data derived from depth electrodes. This ultimately limits diagnostic and therapeutic progress in epilepsy and glioma research. However, this gap also provides a unique opportunity to create a dual-sensing technology that will provide unprecedented insights into the pathogenic mechanisms of human neurologic disease.
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Affiliation(s)
- Luke A Stangler
- School of Engineering, Deakin University, 3216, Geelong, Victoria, Australia
- Division of Engineering, Mayo Clinic, 55905, Rochester, MN, USA
| | - Abbas Kouzani
- School of Engineering, Deakin University, 3216, Geelong, Victoria, Australia
| | - Kevin E Bennet
- School of Engineering, Deakin University, 3216, Geelong, Victoria, Australia
- Division of Engineering, Mayo Clinic, 55905, Rochester, MN, USA
| | - Ludovic Dumee
- School of Engineering, Deakin University, 3216, Geelong, Victoria, Australia
| | - Michael Berk
- School of Medicine, Deakin University, 3216, Geelong, Victoria, Australia
| | | | - Steven Steele
- Division of Engineering, Mayo Clinic, 55905, Rochester, MN, USA
| | - Terence C Burns
- Department of Neurosurgery, Mayo Clinic, 55905, Rochester, MN, USA
| | - Charles L Howe
- Department of Neurology, Mayo Clinic, 55905, Rochester, MN, USA.
- Division of Experimental Neurology, Mayo Clinic, 55905, Rochester, MN, USA.
- Center for MS and Autoimmune Neurology, Mayo Clinic, 55905, Rochester, MN, USA.
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9
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Leroy A, Teixidor J, Bertsch A, Renaud P. In-flow electrochemical detection of chemicals in droplets with pyrolysed photoresist electrodes: application as a module for quantification of microsampled dopamine. LAB ON A CHIP 2021; 21:3328-3337. [PMID: 34250532 DOI: 10.1039/d1lc00116g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The electrochemical quantification of analytes in droplets of PBS separated by a fluorinated phase was investigated. PDMS-fused silica chips with pyrolysed photoresist electrodes were prepared using a simple fabrication technique and used to analyze droplets in flow. Potentiostatic chronoamperometry provided current readouts consistent with mass transport and the concentration inside the droplets. This paper highlights measurements of dopamine in droplets in T-junction microfluidic chips at unprecedently low concentrations, with a limit of detection of 207 nM and a linear range of 0.21-20 μM, giving results similar to continuous flow electrochemistry and allowing the analysis in the striatal extracellular range (<1 μM). The system was applied to the quick and reliable on-line detection of dopamine concentration steps in droplets collected with a microsampling probe in vitro, demonstrating the usefulness of the electrochemical device as a quantification module for microsampled chemicals in droplets.
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Affiliation(s)
- Albert Leroy
- EPFL-STI-IMT-LMIS4, École Polytechnique Fédérale de Lausanne, Station 17, CH-1015 Lausanne, Switzerland.
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10
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Shi N, Mohibullah M, Easley CJ. Active Flow Control and Dynamic Analysis in Droplet Microfluidics. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2021; 14:133-153. [PMID: 33979546 PMCID: PMC8956363 DOI: 10.1146/annurev-anchem-122120-042627] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Droplet-based microfluidics has emerged as an important subfield within the microfluidic and general analytical communities. Indeed, several unique applications such as digital assay readout and single-cell sequencing now have commercial systems based on droplet microfluidics. Yet there remains room for this research area to grow. To date, most analytical readouts are optical in nature, relatively few studies have integrated sample preparation, and passive means for droplet formation and manipulation have dominated the field. Analytical scientists continue to expand capabilities by developing droplet-compatible method adaptations, for example, by interfacing to mass spectrometers or automating droplet sampling for temporally resolved analysis. In this review, we highlight recently developed fluidic control techniques and unique integrations of analytical methodology with droplet microfluidics-focusing on automation and the connections to analog/digital domains-and we conclude by offering a perspective on current challenges and future applications.
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Affiliation(s)
- Nan Shi
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
| | - Md Mohibullah
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
| | - Christopher J Easley
- Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, USA;
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11
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Chae U, Shin H, Choi N, Ji MJ, Park HM, Lee SH, Woo J, Cho Y, Kim K, Yang S, Nam MH, Yu HY, Cho IJ. Bimodal neural probe for highly co-localized chemical and electrical monitoring of neural activities in vivo. Biosens Bioelectron 2021; 191:113473. [PMID: 34237704 DOI: 10.1016/j.bios.2021.113473] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/31/2021] [Accepted: 06/28/2021] [Indexed: 10/21/2022]
Abstract
Investigation of the chemical and electrical signals of cells in vivo is critical for studying functional connectivity and brain diseases. Most previous studies have observed either the electrical signals or the chemical signals of cells because recording electrical signals and neurochemicals are done by fundamentally different methods. Herein, we present a bimodal MEMS neural probe that is monolithically integrated with an array of microelectrodes for recording electrical activity, microfluidic channels for sampling extracellular fluid, and a microfluidic interface chip for multiple drug delivery and sample isolation from the localized region at the cellular level. In this work, we successfully demonstrated the functionality of our probe by monitoring and modulating bimodal (electrical and chemical) neural activities through the delivery of chemicals in a co-localized brain region in vivo. We expect our bimodal probe to provide opportunities for a variety of in-depth studies of brain functions as well as for the investigation of neural circuits related to brain diseases.
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Affiliation(s)
- Uikyu Chae
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; School of Electrical Engineering, Korea University, Seoul, Republic of Korea
| | - Hyogeun Shin
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Nakwon Choi
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology (UST), Daejeon, Republic of Korea
| | - Mi-Jung Ji
- Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Hyun-Mee Park
- Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Soo Hyun Lee
- Department of Medical Records and Health Information Management College of Nursing and Health, Kongju National University, Gongju-si, Chungcheongnam-do, Republic of Korea
| | - Jiwan Woo
- Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Yakdol Cho
- Research Animal Resource Center, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Kanghwan Kim
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Seulkee Yang
- Convergence Research Center for Brain Science, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Min-Ho Nam
- Convergence Research Center for Brain Science, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Hyun-Yong Yu
- School of Electrical Engineering, Korea University, Seoul, Republic of Korea
| | - Il-Joo Cho
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; School of Electrical and Electronics Engineering, Yonsei University, Seoul, Republic of Korea; Yonsei-KIST Convergence Research Institute, Yonsei University, Seoul, Republic of Korea.
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12
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Frank JA, Antonini MJ, Chiang PH, Canales A, Konrad DB, Garwood IC, Rajic G, Koehler F, Fink Y, Anikeeva P. In Vivo Photopharmacology Enabled by Multifunctional Fibers. ACS Chem Neurosci 2020; 11:3802-3813. [PMID: 33108719 DOI: 10.1021/acschemneuro.0c00577] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Photoswitchable ligands can add an optical switch to a target receptor or signaling cascade and enable reversible control of neural circuits. The application of this approach, termed photopharmacology, to behavioral experiments has been impeded by a lack of integrated hardware capable of delivering both light and compounds to deep brain regions in moving subjects. Here, we devise a hybrid photochemical genetic approach to target neurons using a photoswitchable agonist of the capsaicin receptor TRPV1, red-AzCA-4. Using multifunctional fibers with optical and microfluidic capabilities, we delivered a transgene coding for TRPV1 into the ventral tegmental area (VTA). This sensitized excitatory VTA neurons to red-AzCA-4, allowing us to optically control conditioned place preference in mice, thus extending applications of photopharmacology to behavioral experiments. Applied to endogenous receptors, our approach may accelerate future studies of molecular mechanisms underlying animal behavior.
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Affiliation(s)
- James A. Frank
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Marc-Joseph Antonini
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Harvard/MIT Health Science & Technology Graduate Program, Cambridge, Massachusetts 02139, United States
| | - Po-Han Chiang
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Institute of Biomedical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (R.O.C.)
| | - Andres Canales
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - David B. Konrad
- Department of Pharmacy, Ludwig Maximilian University, D-81377 Munich, Germany
| | - Indie C. Garwood
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Harvard/MIT Health Science & Technology Graduate Program, Cambridge, Massachusetts 02139, United States
| | - Gabriela Rajic
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Florian Koehler
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yoel Fink
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Polina Anikeeva
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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13
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Sung C, Jeon W, Nam KS, Kim Y, Butt H, Park S. Multimaterial and multifunctional neural interfaces: from surface-type and implantable electrodes to fiber-based devices. J Mater Chem B 2020; 8:6624-6666. [DOI: 10.1039/d0tb00872a] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Development of neural interfaces from surface electrodes to fibers with various type, functionality, and materials.
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Affiliation(s)
- Changhoon Sung
- Department of Bio and Brain Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
- Daejeon 34141
- Republic of Korea
| | - Woojin Jeon
- Department of Bio and Brain Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
- Daejeon 34141
- Republic of Korea
| | - Kum Seok Nam
- School of Electrical Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
- Daejeon 34141
- Republic of Korea
| | - Yeji Kim
- Department of Bio and Brain Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
- Daejeon 34141
- Republic of Korea
| | - Haider Butt
- Department of Mechanical Engineering
- Khalifa University
- Abu Dhabi 127788
- United Arab Emirates
| | - Seongjun Park
- Department of Bio and Brain Engineering
- Korea Advanced Institute of Science and Technology (KAIST)
- Daejeon 34141
- Republic of Korea
- KAIST Institute for Health Science and Technology (KIHST)
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14
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Frank JA, Antonini MJ, Anikeeva P. Next-generation interfaces for studying neural function. Nat Biotechnol 2019; 37:1013-1023. [PMID: 31406326 PMCID: PMC7243676 DOI: 10.1038/s41587-019-0198-8] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 06/26/2019] [Indexed: 01/06/2023]
Abstract
Monitoring and modulating the diversity of signals used by neurons and glia in a closed-loop fashion is necessary to establish causative links between biochemical processes within the nervous system and observed behaviors. As developments in neural-interface hardware strive to keep pace with rapid progress in genetically encoded and synthetic reporters and modulators of neural activity, the integration of multiple functional features becomes a key requirement and a pressing challenge in the field of neural engineering. Electrical, optical and chemical approaches have been used to manipulate and record neuronal activity in vivo, with a recent focus on technologies that both integrate multiple modes of interaction with neurons into a single device and enable bidirectional communication with neural circuits with enhanced spatiotemporal precision. These technologies not only are facilitating a greater understanding of the brain, spinal cord and peripheral circuits in the context of health and disease, but also are informing the development of future closed-loop therapies for neurological, neuro-immune and neuroendocrine conditions.
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Affiliation(s)
- James A Frank
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Marc-Joseph Antonini
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard/MIT Health Science & Technology Graduate Program, Cambridge, MA, USA
| | - Polina Anikeeva
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA.
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
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15
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Ngernsutivorakul T, Steyer DJ, Valenta AC, Kennedy RT. In Vivo Chemical Monitoring at High Spatiotemporal Resolution Using Microfabricated Sampling Probes and Droplet-Based Microfluidics Coupled to Mass Spectrometry. Anal Chem 2018; 90:10943-10950. [PMID: 30107117 DOI: 10.1021/acs.analchem.8b02468] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
An essential approach for in vivo chemical monitoring is to use sampling probes coupled with analytical methods; however, this method traditionally has limited spatial and temporal resolution. To address this problem, we developed an analytical system that combines microfabricated push-pull sampling probes with droplet-based microfluidics. The microfabricated probe provides spatial resolution approximately 1000-fold better than that of common microdialysis probes. Microfabrication also facilitated integration of an extra channel into the probe for microinjection. We created microfluidic devices and interfaces that allowed manipulation of nanoliter droplet samples collected from the microfabricated probe at intervals of a few seconds. Use of droplet-based microfluidics prevented broadening of collected zones, yielding 6 s temporal resolution at 100 nL/min perfusion rates. Resulting droplets were analyzed by direct infusion nanoelectrospray ionization (nESI) mass spectrometry for simultaneous determination of glutamine, glutamate, γ-aminobutyric acid, and acetylcholine. Use of low infusion rates that enabled nESI (50 nL/min) was critical to allowing detection in the complex samples. Addition of 13C-labeled internal standards to the droplet samples was used for improved quantification. Utility of the overall system was demonstrated by monitoring dynamic chemical changes evoked by microinjection of high potassium concentrations into the brain of live rats. The results showed stimulated neurochemical release with rise times of 15 s. This work demonstrates the potential of coupling microfabricated sampling probes to droplet-based mass spectrometric assays for studying chemical dynamics in a complex microenvironment at high spatiotemporal resolution.
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Affiliation(s)
- Thitaphat Ngernsutivorakul
- Department of Chemistry , University of Michigan , 930 N. University Avenue , Ann Arbor , Michigan 48109 , United States
| | - Daniel J Steyer
- Department of Chemistry , University of Michigan , 930 N. University Avenue , Ann Arbor , Michigan 48109 , United States
| | - Alec C Valenta
- Department of Chemistry , University of Michigan , 930 N. University Avenue , Ann Arbor , Michigan 48109 , United States
| | - Robert T Kennedy
- Department of Chemistry , University of Michigan , 930 N. University Avenue , Ann Arbor , Michigan 48109 , United States.,Department of Pharmacology , University of Michigan , 1150 W. Medical Center Drive , Ann Arbor , Michigan 48109 , United States
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16
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Ngernsutivorakul T, White TS, Kennedy RT. Microfabricated Probes for Studying Brain Chemistry: A Review. Chemphyschem 2018; 19:1128-1142. [PMID: 29405568 PMCID: PMC6996029 DOI: 10.1002/cphc.201701180] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Indexed: 12/13/2022]
Abstract
Probe techniques for monitoring in vivo chemistry (e.g., electrochemical sensors and microdialysis sampling probes) have significantly contributed to a better understanding of neurotransmission in correlation to behaviors and neurological disorders. Microfabrication allows construction of neural probes with high reproducibility, scalability, design flexibility, and multiplexed features. This technology has translated well into fabricating miniaturized neurochemical probes for electrochemical detection and sampling. Microfabricated electrochemical probes provide a better control of spatial resolution with multisite detection on a single compact platform. This development allows the observation of heterogeneity of neurochemical activity precisely within the brain region. Microfabricated sampling probes are starting to emerge that enable chemical measurements at high spatial resolution and potential for reducing tissue damage. Recent advancement in analytical methods also facilitates neurochemical monitoring at high temporal resolution. Furthermore, a positive feature of microfabricated probes is that they can be feasibly built with other sensing and stimulating platforms including optogenetics. Such integrated probes will empower researchers to precisely elucidate brain function and develop novel treatments for neurological disorders.
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Affiliation(s)
| | - Thomas S. White
- Macromolecular Science and Engineering, University of Michigan, 3003E, NCRC Building 28, 2800 Plymouth Rd., Ann Arbor, MI 48109
| | - Robert T. Kennedy
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI 48109
- Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, Ann Arbor, MI 48109
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17
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Lee HJ, Choi N, Yoon ES, Cho IJ. MEMS devices for drug delivery. Adv Drug Deliv Rev 2018; 128:132-147. [PMID: 29117510 DOI: 10.1016/j.addr.2017.11.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 09/06/2017] [Accepted: 11/02/2017] [Indexed: 01/27/2023]
Abstract
Novel drug delivery systems based on microtechnology have advanced tremendously, but yet face some technological and societal hurdles to fully achieve their potential. The novel drug delivery systems aim to deliver drugs in a spatiotemporal- and dosage-controlled manner with a goal to address the unmet medical needs from oral delivery and hypodermic injection. The unmet needs include effective delivery of new types of drug candidates that are otherwise insoluble and unstable, targeted delivery to areas protected by barriers (e.g. brain and posterior eye segment), localized delivery of potent drugs, and improved patient compliance. After scrutinizing the design considerations and challenges associated with delivery to areas that cannot be efficiently targeted through standard drug delivery (e.g. brain, posterior eye segment, and gastrointestinal tract), this review provides a summary of recent advances that addressed these challenges and summarizes yet unresolved problems in each target area. The opportunities for innovation in devising the novel drug delivery systems are still high; with integration of advanced microtechnology, advanced fabrication of biomaterials, and biotechnology, the novel drug delivery is poised to be a promising alternative to the oral administration and hypodermic injection for a large spectrum of drug candidates.
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Affiliation(s)
- Hyunjoo J Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Nakwon Choi
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science & Technology (Biomedical Engineering), KIST School, Korea University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Eui-Sung Yoon
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Il-Joo Cho
- Center for BioMicrosystems, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science & Technology (Biomedical Engineering), KIST School, Korea University of Science and Technology (UST), Daejeon 34113, Republic of Korea.
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18
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Petit-Pierre G, Colin P, Laurer E, Déglon J, Bertsch A, Thomas A, Schneider BL, Renaud P. In vivo neurochemical measurements in cerebral tissues using a droplet-based monitoring system. Nat Commun 2017; 8:1239. [PMID: 29093476 PMCID: PMC5665973 DOI: 10.1038/s41467-017-01419-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 09/15/2017] [Indexed: 11/09/2022] Open
Abstract
Direct collection of extracellular fluid (ECF) plays a central role in the monitoring of neurological disorders. Current approaches using microdialysis catheters are however drastically limited in term of temporal resolution. Here we show a functional in vivo validation of a droplet collection system included at the tip of a neural probe. The system comprises an advanced droplet formation mechanism which enables the collection of neurochemicals present in the brain ECF at high-temporal resolution. The probe was implanted in a rat brain and could successfully collect fluid samples organized in a train of droplets. A microfabricated target plate compatible with most of the surface-based detection methods was specifically developed for sample analysis. The time-resolved brain-fluid samples are analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results provide a time evolution picture of the cerebral tissues neurochemical composition for selected elements known for their involvement in neurodegenerative diseases.
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Affiliation(s)
- Guillaume Petit-Pierre
- Laboratory of Microsystems LMIS4, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - Philippe Colin
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Estelle Laurer
- Unit of Toxicology, CURML, Lausanne University Hospital, Geneva University Hospitals, Lausanne-Geneva, Switzerland
| | - Julien Déglon
- Unit of Toxicology, CURML, Lausanne University Hospital, Geneva University Hospitals, Lausanne-Geneva, Switzerland
| | - Arnaud Bertsch
- Laboratory of Microsystems LMIS4, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Aurélien Thomas
- Unit of Toxicology, CURML, Lausanne University Hospital, Geneva University Hospitals, Lausanne-Geneva, Switzerland.,Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Bernard L Schneider
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Philippe Renaud
- Laboratory of Microsystems LMIS4, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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19
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Sim JY, Haney MP, Park SI, McCall JG, Jeong JW. Microfluidic neural probes: in vivo tools for advancing neuroscience. LAB ON A CHIP 2017; 17:1406-1435. [PMID: 28349140 DOI: 10.1039/c7lc00103g] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Microfluidic neural probes hold immense potential as in vivo tools for dissecting neural circuit function in complex nervous systems. Miniaturization, integration, and automation of drug delivery tools open up new opportunities for minimally invasive implants. These developments provide unprecedented spatiotemporal resolution in fluid delivery as well as multifunctional interrogation of neural activity using combined electrical and optical modalities. Capitalizing on these unique features, microfluidic technology will greatly advance in vivo pharmacology, electrophysiology, optogenetics, and optopharmacology. In this review, we discuss recent advances in microfluidic neural probe systems. In particular, we will highlight the materials and manufacturing processes of microfluidic probes, device configurations, peripheral devices for fluid handling and packaging, and wireless technologies that can be integrated for the control of these microfluidic probe systems. This article summarizes various microfluidic implants and discusses grand challenges and future directions for further developments.
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Affiliation(s)
- Joo Yong Sim
- Electronics and Telecommunications Research Institute, Bio-Medical IT Convergence Research Department, Daejeon, 34129, Republic of Korea
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20
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Kim AA, Kustanovich K, Baratian D, Ainla A, Shaali M, Jeffries GDM, Jesorka A. SU-8 free-standing microfluidic probes. BIOMICROFLUIDICS 2017; 11:014112. [PMID: 28798844 PMCID: PMC5533480 DOI: 10.1063/1.4975026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/17/2017] [Indexed: 06/01/2023]
Abstract
We present a process for fabrication of free-standing SU-8 probes, with a dry, mechanical release of the final micro-devices. The process utilizes the thermal release tape, a commonly used cleanroom material, for facile heat-release from the sacrificial layer. For characterization of the SU-8 microfluidic probes, two liquid interfaces were designed: a disposable interface with integrated wells and an interface with external liquid reservoirs. The versatility of the fabrication and the release procedures was illustrated by further developing the process to functionalize the SU-8 probes for impedance sensing, by integrating metal thin-film electrodes. An additional interface scheme which contains electronic components for impedance measurements was developed. We investigated the possibilities of introducing perforations in the SU-8 device by photolithography, for solution sampling predominantly by diffusion. The SU-8 processes described here allow for a convenient batch production of versatile free-standing microfluidic devices with well-defined tip-geometry.
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Affiliation(s)
| | | | - D Baratian
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
| | - A Ainla
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
| | - M Shaali
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
| | - G D M Jeffries
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
| | - A Jesorka
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
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