Natural melanin-loaded nanovesicles for near-infrared mediated tumor ablation by photothermal conversion

Photothermal therapy requires a biocompatible material to absorb near-infrared (NIR) light and generate sufficient heat. Herein, we suggest natural melanin-loaded nanovesicles (melasicles) as photothermal therapeutic agents (PTA) for NIR mediated cancer therapy in vivo. The mean size of these melasicles was 140 -15 nm. They showed excellent colloidal stability. After irradiation from 808 nm NIR laser at 1.5 W cm^-2, the melasicles showed good photothermal conversion efficiencies both in vitro and in vivo. In drug release study, laser irradiation increased fluidity of vesicle membrane due to photothermal generation from melanin. Initial drug release in the laser irradiation group was higher than that in the no laser irradiation group. After injecting the melasicles into tail veins of CT-26 bearing mice, tumors were suppressed or eliminated after irradiation at 1.5 W cm^-2 for 5 min once or twice. These results suggest that melasicles could be used as attractive PTA for cancer therapy and localized drug release.