Efficiency of the cationic porphyrin, TMPyP4, in inducing cytotoxicity in mouse melanoma cells in vitro : Subcellular localization and photodynamic activity

As a minimally invasive modality, photodynamic therapy achieves selective tumor eradication through the synergistic action of a photosensitizing agent, visible light illumination, and cellular oxygen. Porphyrin-based compounds remain among the most extensively studied photosensitizers because of their favorable photophysical properties and efficient reactive oxygen species generation. In the present study, we investigated the intracellular localization and preliminary photodynamic activity of the cationic porphyrin 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphine in B16F1 mouse melanoma cells [Formula: see text] [Formula: see text]. Confocal fluorescence microscopy combined with organelle-specific probes showed porphyrin localization in the endoplasmic reticulum, Golgi apparatus, and mitochondria after a 1-hour incubation at 1.0 [Formula: see text]g/mL. Minimal nuclear localization was observed. Preliminary viability studies showed that the porphyrin exhibits low dark toxicity but induces significant phototoxicity following irradiation at 650 nm. The strongest photodynamic response was observed at a porphyrin concentration of 0.8 [Formula: see text]g/mL, where mean cell viability fell to approximately 16% compared to about 88% in light-only and dark-porphyrin controls. These findings show that this porphyrin accumulates efficiently in melanoma cells and has favorable properties for photodynamic treatment applications.