The core modification of expanded
porphyrins has been proved to have better photochemical properties, which are favorable for
photodynamic therapy (
PDT) applications. In this context, this study was aimed to investigate the in vitro and in vivo photodynamic activity of one such core-modified expanded
porphyrin, namely,
ammonium salt of 5,10,15,20-tetrakis-(meso-p-sulfonato phenyl)-25,27,29-trithia
sapphyrin. For the in vitro studies, human erythrocytes were used as a membrane semimodel system to investigate the partitioning ability and
drug-uptake characteristics. The partition studies on the membrane semimodel system revealed that maximum partitioning occurs at 12 microgm/mL concentration, and from the
drug-uptake studies it is observed that maximum amount of the sensitizer is bound to the erythrocyte membranes during a 45 min incubation period. Photohemolysis studies at different concentrations of the sensitizer and exposure time showed maximum damage at 5 microgm/mL and 30 min exposure time. In vivo studies were performed on 7,12-dimethylbenz(a)nthracene-induced superficial
squamous cell carcinoma on mouse skin. The sensitizer at a concentration of 2.5% in 2.0%
dimethyl sulfoxide was applied topically on the
tumor spot. After 1 h incubation the
tumor spot was exposed to
laser irradiation from
Nd-YAG laser at its second harmonic wavelength of 532 nm. The photodynamic efficacy was estimated by
tumor volume measurements at regular intervals after the treatment. One month after
PDT exposure a 3.9-fold decrease in the
tumor volume was observed with respect to the
tumor volume before treatment. The treatment efficacy was further confirmed by histological and fluorescence spectroscopic evaluations of the tissue biopsy sample from the treated area. The results of our study suggest that the
ammonium salt of 5,10,15,20-tetrakis-(meso-p-sulfonato phenyl)-25,27,29-trithia
sapphyrin may find possible applications in the new modality of
cancer treatment.