Nongenetic optical neuromodulation with silicon-based materials

Optically controlled nongenetic neuromodulation represents a promising approach for the fundamental study of neural circuits and the clinical treatment of neurological disorders. Among the existing material candidates that can transduce light energy into biologically relevant cues, silicon (Si) is particularly advantageous due to its highly tunable electrical and optical properties, ease of fabrication into multiple forms, ability to absorb a broad spectrum of light, and biocompatibility. This protocol describes a rational design principle for Si-based structures, general procedures for material synthesis and device fabrication, a universal method for evaluating material photoresponses, detailed illustrations of all instrumentation used, and demonstrations of optically controlled nongenetic modulation of cellular calcium dynamics, neuronal excitability, neurotransmitter release from mouse brain slices, and brain activity in the mouse brain in vivo using the aforementioned Si materials. The entire procedure takes ~4–8 d in the hands of an experienced graduate student, depending on the specific biological targets. We anticipate that our approach can also be adapted in the future to study other systems, such as cardiovascular tissues and microbial communities.This protocol describes how to fabricate and apply silicon-based structures for optically controlled neuromodulation. The structures can be used for nongenetic neuronal excitation in cultured neurons, brain slices, and in vivo applications.