The photodynamic therapy of cancer is based on using of photosensitizers (PS) which bind to cells and kill them by singlet oxygen (SO) generated under illumination. These processes were studied in vitro on a model system – bilayer lipid membrane (BLM). We have studied adsorption and photodynamic efficiency of various derivates of porphyrins. The binding of PS to BLM as well as damage of incorporated into it special molecules — SO targets — were monitored by measuring of boundary potential (BP) by a method developed by us earlier. The BP was negative in the case of anions of sulfonated tetraphenylporphyrines (TPPS4) and positive one with cations of b-imidazolyl substituted tetraphenylporphyrine (b-ImTPP) and corresponding Zn(II) complex (b-ImTPPZn). The photodynamic activity of these PS was evaluated as rate R of damage of the SO targets (T) — molecules of di-4-ANEPPS adsorbed on the surface of BLM, under illumination. The rate of oxidation of T molecules adsorbed on (cis) side of the membrane containing PS molecules was compared with that when T were adsorbed on opposite (trans) side. The value of R at cis- side was higher than that at trans- side in contrast to our earlier study when SO was generated by sulfonated aluminum(III) phthalocyanines (1,2). The difference between porphyrins and phthalocyanines was explained by different positions of these PS on the boundary of the membrane.

1. Sokolov V. S., Gavrilchik A. N., Kulagina A. O., Meshkov I. N., Pohl P., Gorbunova Y. G. Voltage-sensitive styryl dyes as singlet oxygen targets on the surface of bilayer lipid membrane. J Photochem Photobiol B. 2016;161: 162-169. 2. Sokolov V. S., Shcherbakov A. A., Tashkin V. Y., Gavril’chik A. N., Chizmadzhev Y. A., Pohl P. Oxidation and lateral diffusion of styryl dyes on the surface of a bilayer lipid membrane. Elektrokhimiya. 2017; 53: 1171-1181.

Financing: Russian Scientific Foundation (# 14-13-01373).