Dosedependent photodynamic effects of 9-acetoxy-2,7,12,17-tetrakis(\-methoxyethyl)-porphycene in vitro.

Porphycenes are chemically pure photosensitizers for topical and systemic photodynamic therapy (PDT). Fast cellular uptake of 9-acetoxy-2,7,12,17-tetrakis-(sB-methoxyethyl)porphycene (ATMPn) has been shown previously.HaCaT human keratinocytes were incubated with ATMPn (1 nmol l(-1) to 1 micromol l(-1) in DMSO or DOPC liposomes). After 1 h, cells were irradiated with different light doses (0, 24, 48J cm(-2)) using an incoherent light source (580-740 nm, 40 mW cm(-2)). Cytotoxic effects were determined by assessing the mitochondrial activity using the MTT assay 24 h following irradiation.Cytotoxic effects were dependent on ATMPn concentration and light dose. Using 20 nmol 1(-1), a 50% decrease of mitochondrial activity (EC(50)) after irradiation with 24 J cm(-2) was achieved. Lowering the ATMPn concentration (10nmol 1(-1)) and increasing the light dose (48 J cm(-2)) yielded the same effect (EC(50)). Maximal decrease of mitochondrial activity (90%) was achieved using ATMPn concentrations of 50-100 nmol l(-1) and a light dose of 24 J cm(-2) or 25 nmol l(-1) ATMPn and 48 Jcm(-2).There was no difference regarding the dose-dependent cytotoxic effects using either ATMPn in DMSO or DOPC liposomes. In the control group (incubation with 1 nmol 1(-1) to 1micromol 1(-1) ATMPn, no irradiation), dark toxicity was not observed.Cell photosensitization with ATMPn was very efficient in vitro yielding the maximal cytotoxic effect at very low ATMPn concentrations as compared to other photosensitizers. Since ATMPn in DMSO and DOPC liposomes revealed the same cytotoxic effects without dark toxicity, theDMSO formulation, which is much easier to prepare, will be preferred in future studies.