Bioelectronic Interfaces for Optical Stimulation of Neurons In-Vitro
ACHILLEAS SAVVA a
a Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, UK
Proceedings of Neural Interfaces and Artificial Senses (NIAS)
Online, Spain, 2021 September 22nd - 23rd
Organizers: Tiago Costa and Georgios Spyropoulos
Oral, ACHILLEAS SAVVA, presentation 022
DOI: https://doi.org/10.29363/nanoge.nias.2021.022
Publication date: 13th September 2021

Optical techniques have greatly accelerated advances in modern medicine. Lasers and optical devices are now established in clinical practice to monitor and improve health condition of patients. Many degenerative diseases affecting the brain and the nervous system could be optically modulated at the cellular level with the right choice of light sensitive materials and devices. Organic semiconducting materials have recently emerged as promising candidates for controlling neuronal activity, both in-vitro and in-vivo. Here we show the development of light sensitive bioelectronic interfaces based on solution processed p- and n-type organic semiconductors that are used to optically stimulate neurons in vitro. These interfaces show good light absorption in a wide range of the visible spectrum (~400 nm – 700 nm) and large photo-electrochemical currents in the range of μA/cm2 when illuminated with low light intensity. Moreover, these interfaces are highly biocompatible as proved by healthy cells cultured directly on their surface as well as other cyto-toxicity assays. Primary cortical neurons extracted from rats are cultured on the surface of the devices for 21 days and form active, interconnected neuron networks. When exposed to low intensity, white light illumination, these neuron networks show a dramatic increase in activity as revealed by calcium imaging. Several individual neurons have shown action potential generation upon illumination – a sudden increase of the membrane potential as measured by patch clamp. By performing a number of photo-electrochemical measurements on the proposed semiconducting interfaces as well as other control substrates, we believe that photo-generated hydrogen peroxide plays a central role in the process of optical stimulation of the neuronal cultures. Despite that the exact mechanisms of photo-stimulation are not yet fully understood, the ability of these interfaces to operate without the need of external wires/bias is an advantage that can be leveraged to build high throughput in vitro models for neuronal network studies.

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