Gold-melanin nanoparticles functionalized with epidermal growth factors for cancer-targeted photothermal therapy

Abstract

Photothermal therapy is a minimally-invasive cancer treatment that uses nanoscopic agents together with near-infrared light (NIR) to destroy cancer cells. Although gold nanorods are the most commonly used photothermal agents, there are certain disadvantages that can decrease the effectiveness of photothermal therapy. Gold nanoparticles address the issues of gold nanorods, but lacks absorbance in the NIR region. Melanin is a well-known biopolymer with a wide absorbance, which extends into the NIR region. Herein, gold and melanin (Gold-melanin) hybrid nanoparticles are developed for photothermal treatment of lung carcinoma. The cancer-targeting functionality is enabled by conjugating epidermal growth factors (EGF) onto the surface of Gold-melanin nanoparticles by using a derivative of polyethylene glycol (PEG) as a spacer. The resulting nanoparticles, termed Gold-melanin@PEG-EGF, exhibit high biocompatibility, excellent dispersion stability in serum, and successful cellular internalization. By using near-infrared irradiation (808 nm, 500 mW $cm^{-2}$), Gold-melanin@PEG-EGF nanoparticles are able to selectively target and kill lung cancer cells after 30 min of irradiation in vitro, while leaving other cell lines (MCF-7 and HaCaT) unharmed. In addition, in vivo photothermal treatments show that Gold-melanin@PEG-EGF nanoparticles are able to suppress tumor growth after 5 min of laser irradiation (808 nm, 1.5 W $cm^{-2}$). The results show that Gold-melanin@PEG-EGF nanoparticles specifically bind to EGF-expressing cells and are able to generate localized hyperthermia to destroy these cells. These unique nanoparticles show great potential as a biocompatible photothermal agent that can effectively kill lung cancer cells