Determination of the photodynamic activity of porphyrins: Potential photosensitizers for treatment of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in people between 65 and 74 years. Recently, the photodynamic therapy (PDT) is used as experimental treatment for exudative AMD. In a PDT process, a reaction takes place when a photosensitiser (PS), light of appropriated wavelength, and oxygen are present at the same time. In general, the PS are porphyrins and related systems. The aim of this study was to evaluate the photodynamic activity (PA) of the Benzoporphyrin (BPH2), Protophorphyrin-IX (Proto), Tetrakis(phydroxyphenyl) porphyrin (THPPH2) and Tetrakis(2-hydroxy-5-nitrophenyl)porphyrin (T2H5NPPH2). The PA is related to quantum yields (??) for the singlet oxygen (1O2.) production. Uric acid, a known singlet oxygen scavenger, is utilised as a chemical dosimeter in the PDT. When the uric acid (UA) and PS solution is irradiated with laser light the UA band absorbance at 293 nm decreases as a rapid evaluation of relative PA of the PS.