Imaging and photocytotoxicity with rhodamine-phenothiazine conjugates

Two Rhodamine-Phenothiazine conjugates, RP1, and RP2, were synthesized, and their photophysical, subcellular localization, and photocytotoxic properties were investigated. We noted robust localization of RP1 in mitochondria and RP2 in mitochondria and lysosome, both in live cells. The fluorophores showed a greater preference for cancer cell accumulation than normal cells. Upon exposure to laser irradiation at low concentrations (50 nM) of these molecules, mitochondrial damage was observed, which led to the lysosomal digestion of damaged mitochondria. RP2 offers dual functionality of real-time inter-organelle interaction (mitochondria-lysosome) in live cells and light-induced ROS production. These fluorophores showed 90% cell viability in dark conditions, whereas laser-treated cell viability was reduced to 75%. The RP1 was further used for mitochondrial targeting in animal models (C.elegans) and successfully showed light-induced ROS production, showing its potential application in photodynamic treatment