An autoreduction method to prepare plasmonic gold-embedded polypeptide micelles for synergistic chemo-photothermal therapy.

Biodegradable, biocompatible polypeptide micelles were used as a reducing agent and template in an autoreduction method for preparing plasmonic gold-embedded polypeptide micelles under mild conditions. The micelles were fully characterized by DLS, TEM, SEM, and AFM. The in situ reduced gold was embedded in the interior core of the disulfide bond-cross-linked polypeptide micelles by forming multivalent Au-S bonds. The plasmonic gold-embedded micelles showed strong near-infrared (NIR) light absorption and NIR-mediated photothermal properties including high photothermal conversion efficiency and good photostability. After continuous-wave diode laser irradiation for 5 min (808 nm, 2 W cm), the NIR light-induced heating of the gold-embedded micelles efficiently killed cancer cells in vitro, as observed by a double fluorescent staining technique. A standard MTT assay, flow cytometry, and fluorescence microscopy showed that the anticancer drug doxorubicin (DOX)-loaded and gold-embedded micelles quickly entered HeLa cells and gave a lower half-maximal inhibitory concentration (IC) than for chemotherapy or photothermal therapy alone, demonstrating a good synergistic effect for the combination chemo-photothermal therapy. Consequently, this work provides a versatile strategy for fabricating plasmonic polypeptide composite nanoparticles, which are promising for synergistic chemo-photothermal cancer therapy.