Melanin-instructed biomimetic synthesis of copper sulfide for cancer phototheranostics

Biomimetic synthesis is a promising strategy for the preparation of nanotheranostics with excellent biocompatibility. Herein, we report a biomimetic approach to synthesize folic acid (FA) modified copper sulfide (CuS) nanodots for cancer phototheranostics by using melanin as a biotemplate and FA as a stabilizer. Owing to the high affinity of melanin for metal ions, copper ions can be adsorbed on the surface of melanin and then reacted with S2− ions to form CuS nanodots. As a natural biomolecule, melanin has high biocompatibility and biodegradability, which can effectively improve the biosafety of the prepared CuS nanodots. More importantly, both melanin and CuS have strong near-infrared (NIR) absorption, the as-prepared CuS-Melanin-FA composite nanoprobes with high photothermal conversion efficiency are promising for augmented photoacoustic imaging and photothermal therapy of cancer, which is demonstrated on 4T1 tumor-bearing mice. Moreover, the biomimetic synthesis method for the preparation of CuS nanodots opens a new horizon for the biomimetic synthesis of other nanotheranostics.