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

Abstract

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.