Photoelectrical Stimulation of Neuronal Cells by an Organic Semiconductor–Electrolyte Interface

Abstract

As a step toward the realization of neuroprosthetics for vision restoration, we follow an electrophysiological patch-clamp approach to study the fundamental photoelectrical stimulation mechanism of neuronal model cells by an organic semiconductor-electrolyte interface. Our photoactive layer consisting of an anilino-squaraine donor blended with a fullerene acceptor is supporting the growth of the neuronal model cell line (N2A cells) without an adhesion layer on it and is not impairing cell viability. The transient photocurrent signal upon illumination from the semiconductor-electrolyte layer is able to trigger a passive response of the neuronal cells under physiological conditions via a capacitive coupling mechanism. We study the dynamics of the capacitive transmembrane currents by patch-clamp recordings and compare them to the dynamics of the photocurrent signal and its spectral responsivity. Furthermore, we characterize the morphology of the semiconductor-electrolyte interface by atomic force microscopy and study the stability of the interface in dark and under illuminated conditions.

Cellular interfaces with hydrogen-bonded organic semiconductor hierarchical nanocrystals

“…7e). Photocapacitivate effects could arise from charging of the QNC surface with negative charges and capacitive coupling 55 , resulting in transient depolarisation of the cell membrane. Recently the phenomenon of fast heating-induced capacitive currents induced by amorphous silicon microparticles in contact with the plasma membrane has been reported by Jiang et al 19 .…”

Nanoscale Polarization‐Resolved Surface Photovoltage of a Pleochroic Squaraine Thin Film

“…2,4‐Bis[4‐( N,N ‐diisobutylamino)‐2,6‐dihydroxyphenyl]squaraine (SQIB) was synthesized as described before . A 6 mg mL −1 solution of SQIB in chloroform (Sigma‐Aldrich; stabilized with amylene) was freshly prepared.…”

“…They are favorable due to their easily tunable properties and capability to readily self‐assemble into a micro‐ or nano‐textured morphology with inherently connected local anisotropic optoelectronic response . The investigated photovoltaic layer blend consists of a phase‐separated squaraine‐fullerene layer blend, which has been shown to stimulate neuronal model cells by local, light‐induced buildup of surface charge . The anisotropy of the sample is determined by the distinct polycrystalline texture of the donor material 2,4‐bis[4‐( N,N ‐diisobutylamino)‐2,6‐dihydroxyphenyl]squaraine (SQIB) (Figure ) and its characteristic Davydov splitting (see also Figure S1, Supporting Information).…”

Organic Bioelectronics: Materials and Biocompatibility

“…However, if films are ‘micropatterned’ with these polymers, good cell adhesion was observed without the need for an additional adhesion layer [41]. Indeed, good cell adhesion was reported for 2,4-bis [4-( N ,Ndiisobutylamino)-2,6dihydroxyphenyl] squaraine (a squaraine-based organic semiconductor), because it spontaneously forms a highly textured surface even when mixed with another semiconductor, e.g., phenyl-C61-butyric-acid-methyl ester (PCBM) [42]. Adhesion can also be a dynamic process since changes in the local chemistry due to cellular secretion or accumulation of metabolites can reduce or improve cell adhesion [34].…”

“…Since the presence of PCBM does not affect the performance of the artificial retina, it would appear that efficient charge generation in the bulk of the photoactive layer is not required for neuronal photostimulation. Another study indicates that the measured transmembrane current is almost entirely explained by a capacitive current; suggesting that no ionic transport occurs through the ion channels in the cell membrane [42]. An exact quantification of the ionic and capacitive current contributions to the total transmembrane current is difficult to establish with standard voltage clamp techniques [87].…”