Photodynamic parameters in the chick chorioallantoic membrane (CAM) bioassay for photosensitizers administered intraperitoneally (IP) into the chick embryo

Abstract

The chick chorioallantoic membrane (CAM) assay was used to determine the photodynamic response (PDR) of blood vessels to Photofrin^®, 5-aminolevulinic acid (ALA), benzoporphyrin derivative monoacid ring A (BPD-MA) and lutetium texaphyrin (Lutex). The photosensitizers were administered systemically via intraperitoneal injection into the chick embryo. Forward stepwise regression analysis of the PDR results enabled the individual contributions of seven experimental variables to be ranked: drug dose, light dose, fluence rate, drug uptake time, vessel type (whether arterioles or venules), vessel diameter, and embryo age. The order of importance of the variables, the PDR profile, was determined for each photosensitizer. Relative contributions of the experimental variables from this study to the CAM PDR were compared with those from our previous study on PDR of CAM blood vessels following topical application of the same photosensitizers. PDR profiles were interpreted in terms of biophysical and biochemical characteristics of the individual photosensitizers and the variation in their interactions with the delivery/distribution environment.