Photovoltaic neural interfaces based on nanowires and quantum dots to restore vision

Optoelectronic biointerfaces have emerged as a promising platform for controlling the nervous system at the cellular, tissue, and organ levels with potential clinical applications via transduction of light energy to ionic currents. In this thesis, we presented a solution-processed photovoltaic nanoassembly comprising a ZnO nanowire (NW) array sensitized with AgBiS2 nanocrystals that enables efficient near-infrared (NIR) neural stimulation through capacitive photocurrents. Nanowires have served as a transformative platform for advanced neural and tissue interfaces. While their photovoltaic properties hold exceptional promise for neural modulation, existing photostimulation approaches predominantly rely on visible-light-activated photoelectrochemical mechanisms. By optimizing nanowire morphology and nanocrystal interdigitation, the platform achieved high charge injection densities (tens of μC cm-2) at low NIR intensities (<1 mW mm-2). The nanoassembly was subretinally placed in an ex-vivo blind rat retina, where it elicited repeatable and robust responses in retinal ganglion cells (RGCs) under NIR pulses. Notably, these responses were achieved at light intensities significantly below established ocular safety limits. We further demonstrated a bioelectronic design where AgBiS2 quantum dots (QDs) served as the photoabsorption material, hole transport medium, and pseudocapacitive electrode–electrolyte interface. The power-law behavior of the anodic and cathodic peaks suggested that diffusion-controlled and capacitive processes contributed to the charge storage mechanism. Furthermore, 3D Bode capacitance maps and phase angle responses indicated a high capacitance of 3.3 mF cm-2 at the half-wave potential (0.044 V vs Ag/AgCl) in artificial cerebrospinal fluid (aCSF). For efficient transduction of light to electrical stimulation, AgBiS2 QDs are embedded onto ZnO NWs in a photovoltaic device architecture, which produced twice the photocurrent (1.9 ± 0.3 mA cm-2) and nearly three times the charge injection (29 ± 2.3 μC cm-2) compared to the planar devices without NWs. Moreover, photostimulation of hippocampal neurons was demonstrated on the device without inducing significant oxidative stress. Collectively, these findings demonstrated an unconventional and efficient bioelectronic device via pseudocapacitive optoelectronic nanocrystals, as well as the nexus of neuronal systems and nanoassemblies, which offers significant potential for enabling unconventional visual prosthetics and advanced neuromodulation therapies. Notably, proven efficacy in eliciting retinal responses within ex vivo models of retinal degeneration underscores its potential for next-generation visual prosthetics and broader neuromodulation applications.