Ultrasensitive Phototriggered Local Anesthesia

An injectable local anesthetic producing repeatable on-demand nerve block would be desirable for pain management. Here we present a phototriggerable device to achieve repeatable and adjustable on-demand local anesthesia in superficial or deep tissues, consisting of gold nanorods attached to low temperature sensitive liposomes (LTSL). The particles were loaded with tetrodotoxin and dexmedetomidine. Near-infrared light (NIR, 808 nm, continuous wave) could heat gold nanorods at low fluence (short duration and low irradiance), leading to rapid release of payload. In vivo, 1–2 min of irradiation at ≤272 mW/cm2 produced repeatable and adjustable on-demand infiltration anesthesia or sciatic nerve blockade with minimal toxicity. The nerve block intensity and duration correlated with the irradiance and duration of the applied light.