Abstract
Photostimulation of neurons by photoactive substrates might revolutionize the treatment of neurological disorders like retinal degeneration, if high-level control of stimulation mechanisms can be achieved. So far these mechanisms have been governed by changing the surface materials interfacing with cells. This study, on the other hand, controls the processes by changing the inner intermediate layer, through proper band engineering. Incorporating appropriate nanoscale materials into organic photovoltaic biointerfaces can enhance their operation at low light intensity, opening a way toward superior neural prosthesis.
Highlights
Light activation of neurons by planar interfaces is a developing field with applications extending from the fundamental examination of neuronal systems to the development of advanced implants such as artificial retinas [1,2]
To resolve the Faradaic and capacitive stimulations, we enhance photogenerated charge density levels by incorporating PbS quantum dots into a poly(3-hexylthiophene-2,5-diyl):([6,6]-Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend. This enhancement stems from the simultaneous increase of absorption, well matched band alignment of PbS quantum dots with P3HT:PCBM, and smaller intermixed phase-separated domains with better homogeneity and roughness of the blend
We use an active layer made of P3HT and PCBM as the donor and acceptor molecules because it is one of the most widely studied and successful photovoltaic blends and has been proven to stimulate neurons grown on the bio-interface
Summary
Light activation of neurons by planar interfaces is a developing field with applications extending from the fundamental examination of neuronal systems to the development of advanced implants such as artificial retinas [1,2]. Photovoltaic substrates have attracted significant attention and the control of the stimulating charge-transfer mechanisms by these substrates is critical for safe and effective cell stimulation. Neural implants in the clinics use two major stimulation mechanisms, which are based on Faradaic and capacitive (non-Faradaic) charge-transfer processes [9,10,11,12,13,14,15]. Charges electrostatically perturb the ions in the electrode/electrolyte interface and lead stimulating currents [16,17]. To resolve the contribution by each mechanism, light intensity levels can be increased, but this can lead to thermocapacitive effects on the membrane [25,26], which need to be minimized to clearly observe the charge-transfer mechanisms
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