Objective: The objective of this study was to investigate the cytotoxicity of octal-bromide zinc phthalocyanine (ZnPcBr8) at different concentrations (0.25, 0.5, and 1 microM) after irradiating HEp-2 cell cultures with two different light sources: a diode semiconductor laser (660 nm, 30 mW) or an LED (640 nm, 70 mW). In order to obtain comparative results, the irradiation parameters of both light sources were adjusted so that the amount of energy density delivered would be the same (4.5 J/cm2).
Background data: Numerous photosensitizers and light sources used in the treatment of human disease have been studied. Based on these studies, a comparative evaluation of two light sources used in photodynamic therapy (PDT) with ZnPcBr8 was proposed.
Materials and methods: HEp-2 cells were incubated with ZnPcBr8 at different concentrations (0.25, 0.5, or 1 microM) for 1 h, irradiated with the diode semiconductor laser (660 nm at 30 mW for 300 sec; 4.5 J/cm2) or the LED laser (640 nm at 70 mW for 128 sec; 4.5 J/cm2), and then incubated in MEM medium for 1 or 24 h. The cells were analyzed using the MTT and trypan blue dye exclusion tests.
Results: The results demonstrated that the concentration of 1 microM of ZnPcBr8 was the most effective after PDT administered by both light sources. According to the MTT results, HEp-2-cell viability decreased by 97.96% 1 h after, and by 99.87% 24 h after irradiation with the diode semiconductor laser, and decreased by 94.03% 1 h after, and by 99.21% 24 h after irradiation with the LED. The results obtained using the trypan blue dye exclusion test confirmed the photodynamic efficacy of ZnPcBr8 employed with both light sources. With regard to HEp-2-cell viability, the following results were observed: a decrease of 98.73% 1 h after, and of 99.49% 24 h after irradiation with the diode semiconductor laser; and a decrease of 98.76% 1 h after, and of 99.23% 24 h after irradiation with the LED.
Conclusions: According to our results with the irradiation parameters studied here, both the LED and diode semiconductor laser can be used for PDT in vitro, since both light sources had excellent photodynamic efficacy.