Abstract
Photosensitizers (PSs) represent a group of molecules capable of generating reactive oxygen species (ROS), such as singlet oxygen (SO); thus, they are considered to be promising agents for anti-cancer therapy. The enhancement of the photodynamic efficiency of these compounds requires increasing the PS activity in the cancer cell milieu and exactly at the target cells. In the present work, we report the synthesis, lipid membrane binding and photodynamic activity of three novel cationic PSs based on β-imidazolyl-substituted porphyrin and its Zn(II) and In(III) complexes (1H2, 1Zn and 1In). Comparison of the behavior of the investigated porphyrins at the bilayer lipid membrane (BLM) demonstrated the highest adsorption for the 1In complex and the lowest one for 1Zn. The photodynamic efficiency of these porphyrins was evaluated by determining the oxidation rate of the styryl dye, di-4-ANEPPS, incorporated into the lipid membrane. These rates were proportional to the surface density (SD) of the porphyrin molecules at the BLM and were roughly the same for all three porphyrins. This indicates that the adsorption of these porphyrins at the BLM determines their photodynamic efficiency rather than the extinction or quantum yield of singlet oxygen.
Highlights
Photodynamic therapy (PDT) is a widely used method for the treatment of skin cancer [1,2,3,4,5] and suggested as a tool for the killing of drug-resistant bacteria [6,7,8,9,10]
The comparison of three porphyrins showed that the highest ∆φb values were revealed in the case of 1In, while the lowest values were achieved for the 1Zn porphyrin
∆φb corresponds to the adsorption of positively charged molecules, which is in agreement with the structures of the porphyrins containing positively charged benzimidazole peripheral groups
Summary
Photodynamic therapy (PDT) is a widely used method for the treatment of skin cancer [1,2,3,4,5] and suggested as a tool for the killing of drug-resistant bacteria [6,7,8,9,10]. The key factors in PDT are photosensitizers (PSs) capable of generating reactive oxygen species (ROS) upon excitation with visible light. Singlet oxygen (SO) is the most prominent and stable example of ROS. SO molecules initiate cell death by the oxidation of proteins, lipids, nucleic acids and carbohydrates of the target cell [2]. Development of PDT techniques requires the synthesis and testing of novel PSs with more efficient and targeted action [1,2,5]. It should be noted that the great impact on the efficiency of PS is related to their ability to precisely bind to the plasma membrane of cancer cells
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