Egg white-mediated green synthesis of CuS quantum dots as a biocompatible and efficient 980 nm laser-driven photothermal agent

Near-infrared (NIR) laser-induced photothermal ablation therapy (PAT) has great potential to revolutionize conventional therapeutic approaches for tumors, and a prerequisite is to obtain biocompatible and efficient photothermal agents. CuS nanomaterials have been demonstrated to be good photothermal agents, and they are usually prepared with organics/polymers as the surface ligands at high temperature (50-300 degrees C). To enhance the biocompatibility and photothermal performance of CuS, herein we develop a green and straightforward method for preparing CuS quantum dots (QDs) by using chicken egg white (CEW) as the surface ligands at physiological temperature (similar to 37 degrees C). CuS QDs have the diameter of 7.1 +/- 0.6 nm and exhibit strong NIR photoabsorption. Under the irradiation of a 980 nm laser with intensity of 0.44 W cm(-2), the CuS QD aqueous dispersions (0.25-1.0 mg mL(-1)) exhibit a temperature elevation of 17.2-37.4 degrees C in 8 min, yielding a photothermal conversion efficiency of 47.2%. Furthermore, CuS QDs exhibit almost no cytotoxicity on cell growth, due to the good encapsulation by highly nutritional proteins from the CEW. More importantly, under the irradiation of a 980 nm laser (0.44 W cm(-2), a low/safe intensity for human skin) for 6 min, cancer cells in vitro and in vivo can be efficiently ablated by the photothermal effects of CuS QDs. Therefore, CuS QDs can be used as a kind of promising, biocompatible and efficient photothermal agent for NIR-PAT of tumors.