Molybdenum sulfide-reduced graphene oxide p-n heterojunction nanosheets with anchored oxygen generating manganese dioxide nanoparticles for enhanced photodynamic therapy.

In an unprecedented approach, p-n heterojunction nanosheets comprising ∼5 nm thick p-type MoS2 nanoplates integrated onto n-type nitrogen doped reduced graphene oxide (n-rGO) have been employed for photodynamic therapy (PDT). When near infrared (NIR) light with 980 nm wavelength was irradiated on this nanocomposite, effective electron-hole separation was obtained across the heterojunction. The nanosheets were modified with lipoic acid functionalized poly(ethylene glycol) to provide better biocompatibility and colloidal stability in physiological solution. The surface decorated 3-5 nm MnO2 nanoparticles (NPs) triggered the disproportionation of intracellular H2O2 which improved generation of reactive oxygen species (ROS) for enhanced PDT cancer therapy, studied in vitro. The role of N-doping in rGO and the effect of immobilization of MnO2 NPs were systematically investigated by control experiments. Our smartly designed p-MoS2/n-rGO-MnO2-PEG nanosheets outperform conventional PDT agents by overcoming limitations such as low absorption band, unfavourable bioavailability and limitations in tissue oxygenation.