A black phosphorus/manganese dioxide nanoplatform: Oxygen self-supply monitoring, photodynamic therapy enhancement and feedback.

Selecting the timing of laser treatment is an important task for improving O2-dependent photodynamic therapy (PDT) efficiency. Here, a black phosphorus-based strategy was developed for dual-mode monitoring oxygen self-supply, enhancing photodynamic therapy, and feeding back therapeutic effect. The hybridized nanoplatform (R-MnO2-FBP) was prepared by assembly of Rhodamine B (RhB)-encapsulated manganese dioxide (R-MnO2) as O2 supplier and indicator, and fluorescein isothiocyanate (FITC)-labelled peptide-functionalized black phosphorus as the theranostic agent. The time-dependent assays suggested that the O2 release was proportional to the liberation of Mn2+ and RhB in the R-MnO2-FBP system. After specific delivery into cancer cells, R-MnO2-FBP was dissociated in the acidic and H2O2-rich environment and generated oxygen to overcome hypoxia-associated PDT resistance. In the meantime, it released both Mn2+and RhB dye, leading to dual-mode (magnetic resonance imaging/fluorescence imaging) monitoring of the oxygen self-supply process. More significantly, the imaging-guided PDT in hypoxic cells displayed 51.6% of cell apoptosis at optimizing timing of laser application, which could also be confirmed by the FITC fluorescence recovery induced by the activated caspase-3 in apoptotic cells. In vivo photonic therapy by R-MnO2-FBP further demonstrated the ability of R-MnO2-FBP to choose the timing of laser application, providing an efficient approach for the enhancement of PDT process.