Optogenetic polymerization and assembly of electrically functional polymers for modulation of single-neuron excitability

Abstract

Ionic conductivity and membrane capacitance are two foundational parameters that govern neuron excitability. Conventional optogenetics has emerged as a powerful tool to temporarily manipulate membrane ionic conductivity in intact biological systems. However, no analogous method exists for precisely manipulating cell membrane capacitance to enable long-lasting modulation of neuronal excitability. Genetically targetable chemical assembly of conductive and insulating polymers can modulate cell membrane capacitance, but further development of this technique has been hindered by poor spatiotemporal control of the polymer deposition and cytotoxicity from the widely diffused peroxide. We address these issues by harnessing genetically targetable photosensitizer proteins to assemble electrically functional polymers in neurons with precise spatiotemporal control. Using whole-cell patch-clamp recordings, we demonstrate that this optogenetic polymerization can achieve stepwise modulation of both neuron membrane capacitance and intrinsic excitability. Furthermore, cytotoxicity can be limited by controlling light exposure, demonstrating a promising new method for precisely modulating cell excitability.

Genetically targeted chemical assembly of polymers specifically localized extracellularly to surface membranes of living neurons

“…To better approach the complexity and plasticity of biological structures, we explored a light-controlled approach, using a genetically encoded photosensitizer [miniSOG ( 20 )] that produces reactive oxygen species upon illumination and could thereby create a membrane-localized reaction center for photopolymerization ( Fig. 6A ); we and others in 2022 had demonstrated an initial version of this possibility but not yet with the next-generation GTCA targeting strategy shown here ( 21 , 22 ). We stained cells 7 days after transfection using our non-detergent–permeabilized and detergent-permeabilized protocols; representative confocal imaging of miniSOG-CD2 neurons ( Fig.…”

Neural repair and regeneration interfaces: a comprehensive review

“…Similar approaches have created PEDOT cloud electrodes that penetrate brain tissue without significantly affecting neural activity [36]. Enzymatic reactions have facilitated gene-targeted polymerization and hold the potential to form insulating structures in the future [37,38]. A cocktail formulation containing hydrogen peroxide, surfactants, and trimmers has achieved enzyme-independent, multi-tissue adaptive in vivo polymerization with reduced primer toxicity [39].…”

Recent Advances in Photosensitizer Materials for Light‐Mediated Tumor Therapy

“…Sessler et al . engineered neural cells to express photosensitive proteins, [96] allowing precise induction of monomer polymerization within cells upon exposure to light (Figure 9a). By accurately controlling the location and density of polymerization, they could actively modulate cell membrane capacitance and cellular signal responses in a controllable manner.…”

“…b) The mechanism of lightcontrolled polymerization in living neurons. Reproduced from ref [96]. Copyright (2023), with permission from American Association for the Advancement of Science.…”