Highly mechanically stable PEDOT:PSS/PDA-modified microelectrode arrays reveal state-specific dynamic neural activity...

Sleep is essential for the modulation of neural functions as well as for preserving physiological balance. However, there is a lack of high-temporal and spatial resolution tools to study the detailed information encoding mechanisms of neurons in deep brain regions over sleep-wake states. In particular, although the regulatory role of the ventral tegmental area (VTA) in sleep-wakefulness has been preliminarily revealed, direct electrophysiological evidence is lacking. To this end, this study fabricated a multi-channel, high-stability microelectrode array (MEA), and adopted a mixed electrochemical co-deposition strategy of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and polydopamine (PDA) to achieve synergistic improvements in the electrode interface. The resulting PEDOT:PSS/PDA coating markedly decreased the impedance from 2085.66 ± 248.87 kΩ (bare Pt) to 28.03 ± 3.25 kΩ, enhanced the charge storage capacity, improved mechanical stability and biocompatibility, and increased the signal-to-noise ratio to 11.61. The coating-modified MEA was implanted into the VTA of mice, enabling stable long-term monitoring of local field potentials (LFPs) and spikes. In parallel, electroencephalography (EEG) and electromyography signals were simultaneously acquired. Through cellular-level neural signal analysis, three neuronal populations with state-specific firing patterns were identified as sleep-responsive, wake-responsive, and state-independent neurons. Further analysis of LFPs revealed that, compared with EEG, they were more sensitive to changes in sleep state and exhibited stronger state-dependent oscillation patterns. This study not only provides new cellular-level evidence for the involvement within the VTA for sleep-wake control, but also presents a general strategy for constructing high-performance, long-term stable neural-electrode interface coatings.