Nanowire based bioprobes for electrical monitoring of electrogenic cells

Real-Time and High-Resolution Monitoring of Neuronal Electrical Activity and pH Variations Based on the Co-Integration of Nanoelectrodes and Chem-FinFETs

Developing new approaches amenable to the measurement of neuronal physiology in real-time is a very active field of investigation, as it will offer improved methods to assess the impact of diverse insults on neuronal homeostasis. Here, the development of an in vitro bio platform is reported which can record the electrical activity of cultured primary rat cortical neurons with extreme sensitivity, while simultaneously tracking the localized changes in the pH of the culture medium. This bio platform features passive vertical nanoprobes with ultra-high signal resolution (several mV amplitude ranges) and Chem-FinFETs (pH sensitivity of sub-0.1 pH units), covering an area as little as a neuronal soma. These multi-sensing units are arranged in an array to probe both chemically and electrically an equivalent surface of ≈ 0.5 mm2. A homemade setup is also developed which allows recording of multiplexed data in real-time (10 ps range) from the active chem-sensors and passive electrodes and which is used to operate the platform. Finally, a proof-of-concept is presented for a neuro-relevant application, by investigating the effect on neuronal activity of Amyloid beta oligomers, the main toxic peptide in Alzheimer's Disease, which reveals that exposure to amyloid beta oligomers modify the amplitude, but not the frequency, of neuronal firing, without any detectable changes in pH values along this process.

Electropolymerization processing of side-chain engineered EDOT for high performance microelectrode arrays

Microelectrode Arrays (MEAs) are popular tools for in vitro extracellular recording. They are often optimized by surface engineering to improve affinity with neurons and guarantee higher recording quality and stability. Recently, PEDOT:PSS has been used to coat microelectrodes due to its good biocompatibility and low impedance, which enhances neural coupling. Herein, we investigate on electro-co-polymerization of EDOT with its triglymated derivative to control valence between monomer units and hydrophilic functions on a conducting polymer. Molecular packing, cation complexation, dopant stoichiometry are governed by the glycolation degree of the electro-active coating of the microelectrodes. Optimal monomer ratio allows fine-tuning the material hydrophilicity and biocompatibility without compromising the electrochemical impedance of microelectrodes nor their stability while interfaced with a neural cell culture. After incubation, sensing readout on the modified electrodes shows higher performances with respect to unmodified electropolymerized PEDOT, with higher signal-to-noise ratio (SNR) and higher spike counts on the same neural culture. Reported SNR values are superior to that of state-of-the-art PEDOT microelectrodes and close to that of state-of-the-art 3D microelectrodes, with a reduced fabrication complexity. Thanks to this versatile technique and its impact on the surface chemistry of the microelectrode, we show that electro-co-polymerization trades with many-compound properties to easily gather them into single macromolecular structures. Applied on sensor arrays, it holds great potential for the customization of neurosensors to adapt to environmental boundaries and to optimize extracted sensing features.

Combining PEDOT:PSS Polymer Coating with Metallic 3D Nanowires Electrodes to Achieve High Electrochemical Performances for Neuronal Interfacing Applications

This study presents a novel approach to improve the performance of microelectrode arrays (MEAs) used for electrophysiological studies of neuronal networks. The integration of 3D nanowires (NWs) with MEAs increases the surface-to-volume ratio, which enables subcellular interactions and high-resolution neuronal signal recording. However, these devices suffer from high initial interface impedance and limited charge transfer capacity due to their small effective area. To overcome these limitations, the integration of conductive polymer coatings, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is investigated as a mean of improving the charge transfer capacity and biocompatibility of MEAs. The study combines platinum silicide-based metallic 3D nanowires electrodes with electrodeposited PEDOT:PSS coatings to deposit ultra-thin (<50 nm) layers of conductive polymer onto metallic electrodes with very high selectivity. The polymer-coated electrodes were fully characterized electrochemically and morphologically to establish a direct relationship between synthesis conditions, morphology, and conductive features. Results show that PEDOT-coated electrodes exhibit thickness-dependent improved stimulation and recording performances, offering new perspectives for neuronal interfacing with optimal cell engulfment to enable the study of neuronal activity with acute spatial and signal resolution at the sub-cellular level.

Plasma-Assisted Atomic Layer Deposition of IrO2 for Neuroelectronics

In vitro and in vivo stimulation and recording of neuron action potential is currently achieved with microelectrode arrays, either in planar or 3D geometries, adopting different materials and strategies. IrO₂ is a conductive oxide known for its excellent biocompatibility, good adhesion on different substrates, and charge injection capabilities higher than noble metals. Atomic layer deposition (ALD) allows excellent conformal growth, which can be exploited on 3D nanoelectrode arrays. In this work, we disclose the growth of nanocrystalline rutile IrO₂ at T = 150 °C adopting a new plasma-assisted ALD (PA-ALD) process. The morphological, structural, physical, chemical, and electrochemical properties of the IrO₂ thin films are reported. To the best of our knowledge, the electrochemical characterization of the electrode/electrolyte interface in terms of charge injection capacity, charge storage capacity, and double-layer capacitance for IrO₂ grown by PA-ALD was not reported yet. IrO₂ grown on PtSi reveals a double-layer capacitance (C_dl) above 300 µF∙cm^-2, and a charge injection capacity of 0.22 ± 0.01 mC∙cm^-2 for an electrode of 1.0 cm², confirming IrO₂ grown by PA-ALD as an excellent material for neuroelectronic applications.

Interfaces Based on Laser-Structured Arrays of Carbon Nanotubes with Albumin for Electrical Stimulation of Heart Cell Growth

Successful formation of electronic interfaces between living cells and electronic components requires both good cell viability and performance level. This paper presents a technology for the formation of nanostructured arrays of multi-walled carbon nanotubes (MWCNT) in biopolymer (albumin) layer for higher biocompatibility. The layer of liquid albumin dispersion was sprayed on synthesized MWCNT arrays by deposition system. These nanostructures were engineered using the nanosecond pulsed laser radiation mapping in the near-IR spectral range (λ = 1064 nm). It was determined that the energy density of 0.015 J/cm² provided a sufficient structuring of MWCNT. The structuring effect occurred during the formation of C–C bonds simultaneously with the formation of a cellular structure of nanotubes in the albumin matrix. It led to a decrease in the nanotube defectiveness, which was observed during the Raman spectroscopy. In addition, laser structuring led to a more than twofold increase in the electrical conductivity of MWCNT arrays with albumin (215.8 ± 10 S/m). Successful electric stimulation of cells on the interfaces with the system based on a culture plate was performed, resulting in the enhanced cell proliferation. Overall, the MWCNT laser-structured arrays with biopolymers might be a promising material for extended biomedical applications.

Lab-on-Chip Microsystems for Ex Vivo Network of Neurons Studies: A Review

Increasing population is suffering from neurological disorders nowadays, with no effective therapy available to treat them. Explicit knowledge of network of neurons (NoN) in the human brain is key to understanding the pathology of neurological diseases. Research in NoN developed slower than expected due to the complexity of the human brain and the ethical considerations for in vivo studies. However, advances in nanomaterials and micro-/nano-microfabrication have opened up the chances for a deeper understanding of NoN ex vivo, one step closer to in vivo studies. This review therefore summarizes the latest advances in lab-on-chip microsystems for ex vivo NoN studies by focusing on the advanced materials, techniques, and models for ex vivo NoN studies. The essential methods for constructing lab-on-chip models are microfluidics and microelectrode arrays. Through combination with functional biomaterials and biocompatible materials, the microfluidics and microelectrode arrays enable the development of various models for ex vivo NoN studies. This review also includes the state-of-the-art brain slide and organoid-on-chip models. The end of this review discusses the previous issues and future perspectives for NoN studies.

Borna disease virus docks on neuronal DNA double-strand breaks to replicate and dampens neuronal activity

Borna disease viruses (BoDV) have recently emerged as zoonotic neurotropic pathogens. These persistent RNA viruses assemble nuclear replication centers (vSPOT) in close interaction with the host chromatin. However, the topology of this interaction and its consequences on neuronal function remain unexplored. In neurons, DNA double-strand breaks (DSB) have been identified as novel epigenetic mechanisms regulating neurotransmission and cognition. Activity-dependent DSB contribute critically to neuronal plasticity processes, which could be impaired upon infection. Here, we show that BoDV-1 infection, or the singled-out expression of viral Nucleoprotein and Phosphoprotein, increases neuronal DSB levels. Of interest, inducing DSB promoted the recruitment anew of vSPOT colocalized with DSB and increased viral RNA replication. BoDV-1 persistence decreased neuronal activity and response to stimulation by dampening the surface expression of glutamate receptors. Taken together, our results propose an original mechanistic cross talk between persistence of an RNA virus and neuronal function, through the control of DSB levels.

•

BoDV-1, its Nucleoprotein or Phosphoprotein cause neuronal DNA double-strand breaks (DSB)

•

DNA double-strand breaks co-localize with BoDV-1 replication factories

•

DNA DSB recruits BoDV-1 replication factories and promotes viral replication

•

BoDV-1 inhibits neuronal activity by impeding surface expression of GluN2A receptors