Proceedings Article | 31 January 1996
KEYWORDS: Photodynamic therapy, Toxicity, In vitro testing, Dermatology, Tumors, Oxygen, Tissues, Skin, In vivo imaging, Absorbance
PDT in dermatology is of growing interest and there are efforts to develop new sensitizers for topical application. Human keratinocytes and dermal fibroblasts were incubated with different concentrations of Acetoxy-tetrakis-(methoxyethyl)-porphycene (ATMPn) for different times and subsequently irradiated with red light (580-740 nm) of different light doses and intensities to determine photodynamic efficacy using a MTT-assay. First, concentrations ranging from 0 ng/ml to 1,000 ng/ml ATMPn (solved in DMEM) were tested (incubation time 24 h, irradiance 80 mW/cm2, total light dose 60 J/cm2). Second, three different light intensities and doses were used for irradiation (47 mW/cm2/35 J/cm2; 80 mW/cm2/60 J/cm2; 107 mW/cm2/80 J/cm2; incubation time 24 h, 100 ng/ml ATMPn). Third, different incubation times of ATMPn (100 ng/ml, 60 J/cm2) were tested (1, 2, 4, 6, 8, 16, 24 h). Using 1 ng, 10 ng and 25 ng/ml, a PDT-effect could not be seen as compared to the dark control group (100%). A significantly high PDT cell mortality rate (94%) was achieved with 100 ng/ml ATMPn yielding a low dark toxicity rate (11%), results with concentrations between 50 and 150 ng/ml were comparable. However, compared to photofrin which served as control (10 (mu) g/ml), dark toxicity rates were significantly lower (Photofrin: 67%). Using different light intensities and doses, best cell killing results were achieved with 60 J/cm2. Comparing different incubation times, no significant differences in cell killing were found. Thus, optimal in vitro parameters for PDT with ATMPn were established using 100 ng/ml ATMPn, about 1- 8 h incubation time and irradiation with 60 J/cm2. As compared to photofrin in previous studies, this novel sensitizer exhibits reduced dark toxicity and similar phototoxicity at a 100-fold lower concentration.
