Fiber-optic photoacoustic enables targeted neuromodulation and stress reduction in mice
Ultrasound neuromodulation offers a non-invasive approach to modulate neural activity in the central nervous system, yet precise, minimally invasive devices capable of targeted stimulation remain limited. A 200 µm diameter fiber-optic photoacoustic emitter (FPE) was developed, coated with a MXene (Ti3C2Tx) and polydimethylsiloxane composite to generate controllable, broadband ultrasonic waves with high spatial precision. Using this FPE to stimulate the medial prefrontal cortex in mice, it was observed marked alleviation of acute social defeat stress-induced emotional stress, evidenced by reduced anxiety-like behavior and increased social interaction. This approach enables near-field, broadband, and tunable ultrasound neuromodulation with potential applications in treating neuropsychiatric disorders involving emotional regulation. The FPE leverages the excellent photothermal stability of Ti3C2Tx under repeated near-infrared (1064 nm) radiation, allowing continuous laser pulses that consistently emit ultrasound. The generated ultrasound can achieve pressures up to several MPa and bandwidths exceeding 20 MHz, supporting detailed imaging and discrimination of tissue microstructure. By integrating in situ ultrasound generation at the fiber tip, shrinking the source-to-target distance to hundreds of micrometers, and naturally reducing far-field energy accumulation and off-target risks, this work demonstrates a highly miniaturized, directional, and broadband ultrasound generator for imaging and sensing applications, particularly in minimally invasive procedures. The study, published in Opto-Electronic Science, represents a significant advancement in targeted neuromodulation for emotional stress modulation.