Photosensitizers (PS) are commonly used in photodynamic therapy to treat skin cancer. PS molecules bind to cell membrane and damage it by singlet oxygen (SO) generated under illumination. In our laboratory, we study in vitro the processes involved in photodynamic therapy on a model bilayer lipid membranes (BLM) by measuring the boundary potential applying the Intramembrane Field Compensation Method (Sokolov and Kuz’min, Biofizika, 25:170, 1980).
This method allowed to monitor the binding of PS on BLM and damage of target molecules (TM) of SO - di-4-ANEPPS under excitation of PS by light. In present investigation, we studied the adsorption and photodynamic efficiency of new positively charged porphyrins, namely b-imidazolyl substituted porphyrin and it’s Zn(II) and In(III) complexes; and two phosphorus (V) complexes of meso-(p-pyridyl)-triphenylporphyrin bearing hydroxyl and ethoxyl axial ligands. We observed a linear dependence of the boundary potential change on the logarithm of concentrations of each PS.
The photodynamic efficiency of these porphyrins was assessed by determining the rate of oxidation (R) of TM adsorbed either on the same or opposite surface of the BLM where molecules PS were present. The values R for both positions of TM were close indicating that BLM is highly permeable to singlet oxygen. The values R were proportional to surface density of the porphyrin molecules in the membrane.
This investigation indicate that the main factor influencing the photodynamic efficiency of the porphyrins is their adsorption on the BLM. The work was supported by the Russian Foundation for Basic Research (project 19-04-00694) and the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» (№ К4-2017-053).
National University of Science and Technology.
NUST-MISiS, Russian Science Foundation, Russian Academy of Sciences.
All authors have declared no conflicts of interest.