Photosensitizers based on porphyrin derivatives as a potential photodynamic agent

Abstract

Photodynamic therapy (PDT) can be defined as the administration of photosensitizer either systemically, locally, or topically to a patient bearing a lesion (frequently but not always cancer), followed after some time by the illumination of the lesion with visible light (usually long wavelength red light). In the presence of molecular oxygen it leads to the generation of cytotoxic species and consequently to cell death and tissue destruction. The singlet oxygen have high reactivity and short half-life. Due to this, PDT directly affects only those biological substrates that are close to the region where these species are generated, usually within a 20 nanometers radius. Therefore, photosensitizers localization is a primary factor in drug release studies to target tissues because it selectivity promotes localized sensitization. In this study, the photosensitive compounds (G0, G1, G2) based on the rings porphyrin were synthesized and characterized (SEM, ATR-IR, NMR, thermal analysis). These molecules were also incorporated into chitosan films. The two step synthesis towards novel macrocycles were elaborated: alkylation reactions and macrocyclization reactions. The photostability of the obtained photosensitizers using high pressure mercury vapour lamp was examined. In the absorption spectra two characteristic bands for the obtained compound are observed: the Soret band located in the range of 300-400 nm and the Q band within 600-800 nm. The amount of produced singlet oxygen at ambient temperature in aerobic conditions was also determined. The lowest value of singlet oxygen quantum yield revealed G0 and the highest revealed G1. The aggregation study was also performed. This phenomenon is well-known especially for phthalocyanines and porphyrin derivatives. The results of the obtained compounds were compared with the results of the commercially available porphyrins.

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The project was supported by research grant: National Science Centre 2015/19/N/NZ7/02934