Non-invasive Deep-brain Optogenetic fMRI Mediated by 808 nm Infrared-sensitized Upconversion Nanoparticles

Abstract

Typically, optogenetic fMRI is presented at the target region through an implanted optical fiber. Despite the use of small fibers that range from 100µm-400µm in diameter that will ensure minimal brain tissue injury during insertion, it remains an invasive procedure as small brain regions could be easily damaged. In this study, we aim to demonstrate a solution to make non-invasive optogenetic stimulation viable, particularly when used in combination with fMRI to stimulate deep brain regions. We propose the use of our recently developed upconversion nanoparticles (UCNPs), which can be triggered to emit blue light by penetrative near-infrared light (NIR; 808nm) and excite channelrhodopsins (ChR2) expressed in ventral posteromedial (VPM) thalamocortical excitatory neurons.