Rationally Designed Ru(II) Complex with Dual Type I/II ROS Generation for Hypoxia-Tolerant Photodynamic Therapy in Melanoma

The hypoxic tumor microenvironment of melanoma imposes a critical limitation on conventional type II photodynamic therapy (PDT), relying on oxygen for the generation of cytotoxic reactive oxygen species (ROS). To overcome this challenge, a donor-π-acceptor (D-π-A) bis-terpyridine ruthenium(II) complex, Ru(tpy)2TT, was rationally designed and synthesized to enable dual type I/II ROS generation. The ROS production efficiency was quantitatively evaluated in B16 murine melanoma cells, and the antitumor efficacy was assessed in a syngeneic C57BL/6N mouse melanoma model. Upon photoactivation at 500 nm, Ru(tpy)2TT efficiently generated both superoxide anion (type I ROS) and singlet oxygen (type II ROS). Intratumoral administration followed by localized irradiation resulted in an 80% reduction in tumor volume after 10 days, with no observed systemic toxicity or off-target effects. These findings demonstrate that Ru(tpy)2TT circumvents hypoxia-induced PDT resistance in melanoma via hypoxia-tolerant and oxygen-dependent ROS pathways, establishing its potential as a targeted precision antitumor agent. Furthermore, this work provides a generalizable molecular design strategy for developing hypoxia-tolerant PDT agents for refractory melanoma.