Ruthenium(II) complexes coordinated to graphitic carbon nitride: Oxygen self-sufficient photosensitizers which produce multiple ROS for photodynamic therapy in hypoxia

The photodynamic therapy (PDT) of cancer is limited by tumor hypoxia as PDT efficiency depends on O-2 concentration. A novel oxygen self-sufficient photosensitizer (Ru-g-C3N4) was therefore designed and synthesized via a facile one-pot method in order to overcome tumor hypoxia-induced PDT resistance. The photosensitizer is based on [Ru(bpy)(2)](2+) coordinated to g-C3N4 nanosheets by Ru-N bonding. Compared to pure g-C3N4, the resulting nanosheets exhibit increased water solubility, stronger visible light absorption, and enhanced biocompatibility. Once Ru-g-C3N4 is taken up by hypoxic tumor cells and exposed to visible light, the nanosheets not only catalyze the decomposition of H2O2 and H2O to generate O2, but also catalyze H2O2 and O-2 concurrently to produce multiple ROS ((OH)-O-center dot, O-center dot(2)- , and O-1(2)). In addition, Ru-g-C3N4 affords luminescence imaging, while continuously generating O-2 to alleviate hypoxia greatly improving PDT efficacy. To the best of our knowledge, this oxygen self-sufficient photosensitizer produced via grafting a metal complex onto g-C3N4 is the first of its type to be reported.

Automated summary

The novel oxygen self-sufficient photosensitizer Ru-g-C3N4, designed to overcome tumor hypoxia-induced resistance in photodynamic therapy, shows enhanced water solubility, visible light absorption, and biocompatibility. Through catalyzing decomposition of H2O2 and H2O to generate O2, Ru-g-C3N4 significantly improves PDT efficacy by producing multiple reactive oxygen species and alleviating tumor hypoxia. This metal complex-grafted g-C3N4 photosensitizer represents a groundbreaking development in oxygen-producing photodynamic therapy agents.