PHOTOPHYSICAL PROPERTIES OF PORPHYRINS IN BIOLOGICAL-MEMBRANES

This review illustrates the photophysical properties of some porphyrin s, especially those used for biomedical applications, in relation to t heir photosensitizing efficiency in biological membranes. Porphyrin ab sorption and luminescence properties are mainly examined. The factors influencing the affinity of porphyrins for biological membranes, inclu ding the dye hydrophobicity, the charge and aggregation state, the pH of the medium and the physicochemical properties of the dye environmen t, are discussed. These factors determine the differences in the photo physical properties of porphyrins in biological membranes. Particular attention is paid to the porphyrin aggregation state: only monomeric s pecies and possibly planar end-to-end aggregates are endowed with sign ificant photosensitizing ability. Many conclusions presented are based on data obtained on membrane model systems such as micelles or liposo mes which can mimic specific situations occurring in cells.