Mitochondria-targeting properties and photodynamic activities of porphyrin derivatives bearing cationic pendant

Four meso-tetraphenylporphyrin derivatives bearing either triphenylphosphonium ion-(P1 and P2) or triethylammonium ion-(P3 and P4) terminated alkoxy group at either para-(P1 and P3) or meta-(P2 and P4) position of one meso-phenyl group were designed and synthesized. P1–P4 show similar absorption and fluorescence emission spectra and 1O21O2 quantum yields. The more lipophilic nature of triphenylphosphonium ion over triethylammonium ion renders P1 and P2 higher octanol/water partition coefficients than P3 and P4. Confocal fluorescence microscopy proved that P1–P4 are all mitochondria-targeting. MTT assay showed that P1–P4 presented significant phototoxicity at the concentrations that dark toxicity is negligible towards human breast cancer cell line MCF-7 cells, displaying their application potential in PDT.