SPECTROSCOPIC STUDIES OF TIN ETHYL ETIOPURPURIN IN HOMOGENEOUS AND HETEROGENEOUS SYSTEMS

Tin ethyl etiopurpurin is a promising second generation photosensitize r for photodynamic treatment of cancer. This compound is only poorly s oluble in aqueous media and, therefore, needs a delivery system for ad ministration to animals. Successful tumor eradication has previously b een reported, following light exposure of rats previously administered with the purpurin formulated as a Cremophor El emulsion, in dipalmito yl-phosphatidyl-choline liposomes or with gamma cyclodextrins. In this paper, we describe some absorbance and fluorescence studies of tin et hyl etiopurpurin in homogeneous and heterogeneous systems. In general, absorption and emission maxima were found to be red shifted as the en vironment changed from polar to non-polar. The viscosity and dielectri c constant of the medium affected the purpurin fluorescence intensity. The liposome preparations were characterized by particle size determi nation, differential scanning calorimetry and by sensitizer fluorescen ce quenching studies. Photobleaching studies also showed variation owi ng to changes in the environment in which the dye was located.