A serine protease photodynamic inhibition by phthalocyanines: effect of light spectra

Abstract The photosensitive compounds have been settled as capable to be involved in a wide collection of photo-physicochemical developments for biomedical and ecological applications. This is based on their ability of light absorption in the ultraviolet-visible or near IR spectra with formation of reactive species with ability to be of advantage to the photodynamic mechanisms of action. The present study describes a readily accessible, reproducible and easy to be used method for evaluation of the potentiation of photosensitizers’ and matching light on a chymotrypsin enzymic activity. This assessment of photosensitive compounds may have benefit in photodynamic therapy (PDT). Octa-substituted phthalocyanine complexes of gallium and zinc (GaPc and ZnPc) were used to evaluate the enzymic inhibition which may occur during the photosensitization at two different irradiation spectra. The light sources such as UV lamp (254 nm) and red light-emitting diode (LED 660 nm) were applied. A casein was used as a substrate and the proteolytic activity was monitored by a substrate absorption. The results suggested that a proper light excitation of GaPc with LED 660 nm fully inhibited the enzymatic activity of ChT. The irradiation with UV 254 nm of ChT incubated with phthalocyanines led to screening effect on proteolytic activity in comparison to samples with UV light. The study shows promising potential of the method for an efficient evaluation of the effectiveness of novel photosensitizers.