Figure 12.

UCNP-mediated NIR upconversion optogenetics for deep brain stimulation. (A) Schematic principle of UCNP-mediated NIR upconversion optogenetics. (B) Transmission electron microscopy images of the silica-coated UCNPs. (C) Emission spectrum of the nanoparticles upon excitation at 980 nm. (Inset) Upconversion emission intensity of UCNPs as a function of excitation intensity at 980 nm. (D) Scheme of in vivo fiber photometry for measuring UCNP-mediated NIR upconversion in deep brain tissue. The tip of an optic fiber, transmitting NIR excitation light, was positioned at various distances from the ventral tegmental area (VTA) where UCNPs were injected. Modified with permission from Chen et al. (2018).