Photodynamic activity on human erythrocytes by a newly synthesized sensitizer - trithia sapphyrin sulfonate: A preliminary report

A new photosensitizer, Trithia Sapphyrin was synthesized with 3 sulfurs and 2 nitrogen inside the macrocycle. The relative effectiveness is influenced by molecular properties, which control the penetration and distribution of the sensitizer in the system prior to the photon capture. To be precise, the effectiveness of the sensitizer depends on (1) the ability to partition from the bathing medium to a region of the cell membrane where it is exposed to a low polarity environment (2) ability to absorb light in such a low polarity environment (3) its triplet quantum yield in this environment. In view of these factors, the partition coefficient for different concentrations, ranging from 1 to 50 μg/ml of trithia sapphyrin in the Octanol/Saline system was determined. The partition coefficient for 5 μg/ml is observed to be the highest, which indicated the higher partitioning of trithia sapphyrin towards the octanol phase i.e. towards the membrane. The uptake of sensitizer was analyzed in 0.05% hematocrit for different periods of incubation ranging from 5 minutes to 5 hour, in order to find (1) binding of sensitizer to the cell membrane (2) partition of the sensitizer molecule between the aqueous phase and lipid phase and (3) diffusion of the pigment molecule into the intracellular aqueous phase. With these observations, Photohemolysis studies were carried out for different pre and post incubation time as a function of light dose and sensitizer concentration.