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Aluminium phthalocyanines sulfonated to a different degree ( AlPcS n) and consisting of various isomeric species were studied by spectroscopic techniques to determine their tendencies to form dimers and aggregates. These characteristics were compared with the cell-penetrating properties of the species, using the Ehrlich ascites mouse tumor cell line, to arrive at structure-activity relationships. AlPcS n preparations consisting of the least number of isomeric species exhibited the highest tendency to form dimers and aggregates, whereas the more complex preparations, consisting of many isomeric products, showed more consistent monomeric features in aqueous environments. Uptake in cells was shown to correlate well with the overall hydrophobicity of the preparation and inversely with its degree of aggregation in the extracellular environment. Among the purified, single isomeric AlPcS n the amphiphilic disulfonated AlPcS 2a , enriched in positional isomers featuring sulfonate groups on adjacent phthalic subunits, showed the best membrane-penetrating properties. Even higher cell uptake was observed for the AlPcS 2mix reflecting a combination of optimal lipophilicity and a low degree of aggregation. Similarly, in the case of AlPcS 4, the pure isomeric compound showed less cell uptake than the mixed isomeric preparation of similar hydrophobicity, reflecting the higher degree of aggregation invoked by its symmetrical structure. Our data indicate that mixed sulfonated phthalocyanine preparations may exert higher photodynamic efficacy in biological applications as compared to the pure isomeric constituents.

— Measurement of singlet oxygen production by porphyrin-type photosensitizers in simple buffer solutions show that TPPS is more efficient than PII (Photofrin II) or than hematoporphyrin. This behavior was observed using three independent analytical detection methods for 1O2: RNO bleaching, tryptophan degradation, and oxygen consumption. Similar results were obtained when irradiating with a classical light source or with a pulsed dye laser. Addition of EPC liposomes to the buffer solution caused a decrease of efficiency for TPPS and an increase for PII. Addition of BSA shows the same relative pattern: a small increase of efficiency for TPPS and a tenfold increase for PII. These changes can be ascribed to specific interactions between the sensitizer molecules and the organized medium. Since changes in the fluorescence properties are also due to interactions with the medium, we monitored the emission of the sensitizers as a function of the environment. The fluorescence peak positions (at 648, 705 nm for TPPS and at 615, 677 nm for PII) were all red shifted. The intensities show an increase, particularly for PII in liposomes, due to a marked change in the microviscosity.