SPECTROSCOPY AND PHOTOSENSITIZATION OF SAPPHYRINS IN SOLUTIONS AND BIOLOGICAL-MEMBRANES

A spectroscopic and photophysical study of three new sapphyrin molecul es is presented. The sapphyrin backbone that was derivatized to make t hem water soluble possesses an absorption band around 700 nm, a desire d property for biological photosensitization. We studied the absorptio n and fluorescence spectra, from which evidence for aggregation in sol vents of different polarities was obtained. The extent of aggregation is correlated with the nature of the attached moiety. The absolute qua ntum yields of singlet oxygen production were measured, with 1,3-diphe nyl isobenzofuran as a model target, and were 0.13-0.18 in ethanol. Th e binding constants to liposomes and to cells were determined spectros copically and were found to correspond to the hydrophobicities of the compounds, with an additional effect, ascribed to the sugar moiety, wh ich was found in the case of one of the sapphyrins. The efficiency of photodamage to Staphylococcus aureus by sapphyrins and hematoporphyrin was equivalent, on the basis of cells killed per microgram of sensiti zer in the incubation mixture.