Chenais, N. A. | bioRxiv Science

bioRxiv2020

Tailored polymeric, photovoltaic, and near-infrared-responsive neuroprosthesis

Organic materials, such as conjugated polymers, are attractive building blocks for bioelectronic interfaces. In particular, organic semiconductors showed excellent performances in light-mediated excitation and silencing of neuronal cells and tissues. However, the main challenges of these organic photovoltaic interfaces compared to inorganic prostheses are the limited stability of conjugated polymers in the aqueous environment and the exploitation of materials only responsive in the visible spectrum. In this report, we show a new photovoltaic organic interface tailored for neuronal stimulation in the near-infrared spectrum. Also, we adjusted the organic materials by chemical modification in order to improve the stability in aqueous environment and to modulate the photoelectrical stimulation efficiency. As proof of principle, we tested this interface for retinal stimulation. Our results provide an efficient, reliable, and stable implant applicable for neural stimulation.

bioengineering↗

bioRxiv2019

Photovoltaic stimulation efficiently evokes network-mediated activity of retinal ganglion cells

ObjectivePhotovoltaic retinal prostheses theoretically offer the possibility of standalone high-resolution electrical stimulation of the retina. However, in artificial vision, achieving locally selective epiretinal stimulation is particularly challenging, on the grounds of axonal activation and electrical cell coupling.\n\nApproachHere we show that electrical and photovoltaic stimulation of dystrophic retinal circuits with capacitive-like pulses leads to a greater efficiency for indirect network-mediated activation of retinal ganglion cells. In addition, a biophysical model of the inner retina stimulation is proposed to investigate the waveform and duration commitments in the genesis of indirect activity of retinal ganglion cells.\n\nMain resultsBoth in-vitro and in-silico approaches suggest that the application of long voltage pulses or gradual voltage changes are more effective to sustainably activate the inner excitatory and inhibitory layers of the retina, thus leading to a reproducible indirect response. The involvement of the inhibitory feedback from amacrine cells in the forming of indirect patterns represents a novel biological tool to locally cluster the response of the retinal ganglion cells.\n\nSignificanceThese results demonstrate that recruiting inner retina cells with epiretinal stimulation enables not only to bypass axonal stimulation but also to obtain a more focal activation thanks to the natural lateral inhibition. In this perspective, the use of capacitive-like waveforms generated by photovoltaic prostheses may allow improving the neural response resolution while standing high-frequency stimulation.

neuroscience↗