Abstract
The technology for producing microelectrode arrays (MEAs) has been developing since the 1970s and extracellular electrophysiological recordings have become well established in neuroscience, drug screening and cardiology. MEAs allow monitoring of long-term spiking activity of large ensembles of excitable cells noninvasively with high temporal resolution and mapping its spatial features. However, their inability to register subthreshold potentials, such as intrinsic membrane oscillations and synaptic potentials, has inspired a number of laboratories to search for alternatives to bypass the restrictions and/or increase the sensitivity of microelectrodes. In this study, we present the fabrication and in vitro experimental validation of arrays of PEDOT:PSS-coated 3D ultramicroelectrodes, with the best-reported combination of small size and low electrochemical impedance. We observed that this type of microelectrode does not alter neuronal network biological properties, improves the signal quality of extracellular recordings and exhibits higher selectivity toward single unit recordings. With fabrication processes simpler than those reported in the literature for similar electrodes, our technology is a promising tool for study of neuronal networks.
Highlights
Recording and mapping the electrical activity of neurons in vivo, with adequate spatiotemporal resolution to capture both their action potentials and complex synaptic interactions, represents the holy grail of neurotechnology
While PEDOT coatings previously decreased the impedance of 15-μm-large microelectrodes (Ludwig et al, 2011), here we demonstrate for the first time how PEDOT:PSS coating of 3D ultramicroelectrodes allows a similar final result
We aimed to demonstrate the possibility of novel microelectrode arrays (MEAs) fabrication with low impedance ultramicroelectrodes, exhibiting in comparison to standard MEAs an adequate signalto-noise ratio, an improved selectivity for single units and a proper stability throughout long-term recordings
Summary
Recording and mapping the electrical activity of neurons in vivo, with adequate spatiotemporal resolution to capture both their action potentials and complex synaptic interactions, represents the holy grail of neurotechnology. Disentangling neuronal electrical activity and network communications is a key step towards an in-depth understanding of the nervous system during behavior, sensation, memory, and cognition. Refinement and technology optimization in vitro is pivotal for later translating the prototypes to an in vivo nervous system, and two main electrophysiological approaches were first devised in vitro: (1) intracellular recordings from single neurons, characterized by a high temporal accuracy, selectivity and sensitivity but low spatial resolution while causing irreversible cell damage; and (2) extracellular recordings by microelectrode arrays (MEAs), capable of simultaneously accessing the electrical activity from a large number of cells over long time periods, but lacking sensitivity to subthreshold membrane potentials. Further scientific studies, focused on electrical, electrochemical, physical, and physicochemical properties of microelectrodes and cells are urgently needed
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