Synergistic Chemo-Photothermal Suppression of Cancer by Melanin Decorated MoO x Nanosheets.

Two-dimensional (2D) nanomaterials able to effectively absorb near-infrared (NIR) radiation have shown considerable potential as multifunctional platforms in the treatment of cancer. Here, we report a molybdenum dioxide (MoO x )-based system for synergistic chemo- and photothermal therapy of cancer. MoO x nanosheets were generated via a one-step hydrothermal route, grafted with poly(ethylene glycol) (PEG), and decorated with melanin (Mel), with successful functionalization confirmed by IR spectroscopy. The mean diameter and thickness of the MoO x particles were found to be 302 ± 34 nm and 19 ± 2 nm using atomic force microscopy. The hydrodynamic size of the MoO x nanosheets was 105 ± 17 nm, and the resulting final MoO x -PEG-Mel-DOX nanocomposite formulation had a uniform diameter of 161 ± 26 nm. The MoO x -PEG-Mel nanosheets efficiently convert NIR light to heat, possessing a photothermal conversion efficiency of 61.7%. They can also be loaded with doxorubicin hydrochloride (DOX), giving a high drug loading (325.6 mg DOX/g MoO x -PEG-Mel). DOX release from the formulation is influenced by both pH and NIR irradiation. Systematic in vitro and in vivo evaluations reveal that synergistic chemo- and photothermal therapy using MoO x -PEG-Mel-DOX can completely eradicate a tumor with no observable off-target cytotoxicity. This is the first report of the fabrication of enhanced photothermal agents by combining MoO x nanosheets and a natural product. This work proffers a strategy for efficiently treating cancer as well as potentially extending the photothermal applications of 2D nanomaterials by surface melanin functionalization.