Investigation into Novel Mitochondrial Targeting Cyanine Dyes as Potential Photosensitizing Agents for Photodynamic Therapy

Carbocyanine dyes are a class of organic compounds with high conjugation that enable them to act as photosensitizing agents in photodynamic therapy (PDT). These compounds can be equipped with the triphenyl phosphonium group which directs compounds into the mitochondria. Three near-infrared quinolinium carbocyanine dyes containing a triphenyl phosphonium with a meso substituted pentamidine bridge (hydrogen, bromine or chlorine) were tested for their spectroscopic and photochemical properties. It was found that the hydrogenated compound was not stable in at pH 7 and thus not explored further. It was then discovered that the bromo while stable, had issues during gel electrophoresis inducing a precipitating effect not allowing for proper analysis. The chlorinated form though was stable and was able to photo-cleave DNA (pH 7.0, 10 degrees C, 830nm). Our results show DNA minor groove interaction and Type 1 electron transfer photoreactions to generate DNA-damaging hydroxyl radicals