Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for topically applied photosensitizers

The relative efficacy of Photofrin(R)-based photodynamic therapy (PDT) has been compared with that of the second-generation photosensitizers 5-aminolevulinic acid (ALA), sulfonated chloro-aluminum phthalocyanine (AlPcSn), benzoporphyrin derivative monoacid ring A (BPD-MA), and lutetium texaphyrin (Lutex). PDT-induced vascular damage in the chick chorioallantoic membrane (CAM) is measured following topical application of the photosensitizers. In order to make meaningful comparisons, carl is taken to keep treatment variables the same. These include light dose (5 and 10 J/cm(2)), power density (33 and 100 mW/cm(2)), and drug uptake time (30 and 90 min). The drug dose ranges from 0.1 mu g/cm(2) for BPD to 5000 mu g/cm(2) for ALA. Results are also analyzed statistically according to CAM vessel type (arterioles versus venules), vessel diameter, and vessel development (embryonic age). For each photosensitizer, the order of importance for the various PDT parameters is found to be unique. The differences between the sensitizers are most likely due to variation in biophysical and biochemical characteristics, biodistribution, and uptake kinetics. (C)1999 Elsevier Science S.A. All rights reserved.