Influence of H2TOEtPyP4 porphyrin on the stability and conductivity of bilayer lipid membranes.

Many water-soluble cationic porphyrins are known to be prospective chemotherapeutics and photosensitizers for cancer treatment and diagnosis. The physicochemical properties of porphyrins, in particular their interactions with membranes, are important determining factors of their biological activity. The influence of cationic meso-tetra-[4-N-(2'-hydroxyethyl) pyridyl] porphyrin (H2TOEtPyP) on the stability and conductivity of bilayer lipid membranes (BLMs) was studied. H2TOEtPyP4 porphyrin was shown to decrease the stability of BLMs made of a mixture of DOPS and DPPE (1:1) in an electric field because of a reduction of line tension of spontaneously formed pore edges in the BLM. The presence of cationic porphyrin was found to reduce BLM surface tension. This effect was enhanced with increasing porphyrin concentration. H2TOEtPyP4 increased the probability of spontaneous pore formation. Further investigating the cyclic current-voltage characteristics of BLMs allowed determining the electrical capacity and conductivity of BLMs in the presence of H2TOEtPyP4 porphyrin. It was shown that in the presence of cationic porphyrin the electrical capacity as well as conductivity of the BLM increases.