A hydrogen peroxide responsive resorufin-based phototheranostic agent for selective treatment of cancer cells

Enhanced selectivity towards cancer cells is one of the most essential features sought in new generation photodynamic therapy (PDT) agents in order to minimize the side effects on healthy cells and to improve the efficacy of the treatment. In this direction, one promising approach is to design activatable photosensitizers, which tend to stay in an OFF state and get activated only in cancer cells with tumor-associated stimuli. Based on this idea, herein we introduced a hydrogen peroxide (H2O2) activatable iodinated resorufin (RR-1) as a redshifted, water soluble and cancer cell selective photosensitizer. RR-1 exhibited high singlet oxygen quantum yield in aqueous solutions upon reacting with H2O2 and induced selective photocytotoxicity in colorectal (HCT116) and triple negative breast (MDA MB-231) cancer cells, which contain high level of reactive oxygen species (ROS). Additionally, fluorescence signal of the iodo-resorufin core was restored upon cleavage of the cage unit in these cancer cells. In contrast, very low photocytotoxicity and negligible fluorescence enhancement were observed in normal fibroblast (NIH-3T3) cells. RR-1 not only marks the first example of a H2O2 activatable resorufin-based photosensitizer but also represents the first ever resorufin-based theranostic agent. We anticipate that iodo-resorufin scaffold can be easily modified with different masking units towards realization of highly selective and efficient phototheranostic agents for treatment of various cancer cells.

Automated summary

The study introduced a H2O2 activatable iodinated resorufin as a redshifted, water soluble and cancer cell selective photosensitizer, exhibiting high singlet oxygen quantum yield and selective photocytotoxicity in colorectal and triple negative breast cancer cells, while showing almost no impact on normal cells.