Fiber-optic platform for infrared laser thermogenetic stimulation and multimodal optical readout in freely moving animals

Thermogenetics is a bioengineering technique that enables control of cellular activity via temperature-sensitive ion channels and externally applied heating. We present a fiber-optic platform for infrared laser thermogenetic stimulation combined with the simultaneous optical readout of fluorescent biosensors and temperature in the brain of freely moving animals. Infrared light delivered through a reconnectable double-clad optical fiber enables spatially localized heating of neural tissue, eliciting reproducible behavioral responses via the human transient receptor potential vanilloid 1 (hTRPV1) channel. The same platform supports multimodal optical measurements, including all-optical thermometry based on nitrogen-vacancy (NV) centers in diamonds and dual-wavelength excitation fluorescence detection. The temperature was retrieved from the zero-phonon line (ZPL) of NV^- fluorescence, providing an experimentally demonstrated sensitivity of 16 mK·Hz^-0.5, with a shot-noise-limited performance reaching 1.2 mK·Hz^-0.5. This integrated and scalable approach allows for precise thermal neuromodulation while enabling flexible integration with genetically encoded fluorescent sensors.