In order to increase the penetration of HpD through the skin and to prevent photosensitization from occurring in normal skin after systemic administration, HpD was encapsulated into topical form of liposomes, composed of egg phosphatidylcholine and cholesterol 6.5-1 (molar ratio). Multilamellar vesicles (MLV) and vesicles prepared by dehydration rehydration procedure (DRV) were tested. The topical delivery of the liposomally encapsulated HpD was measured in vitro on Hairless female rat biopsies by a stripping technique and spectrofluorimetry. We have got the following results: (1) The encapsulation ration ranged from 5% to 12% according to the liposome's type. (2) The penetration of liposomal HpD into the 10th strip was better for the MLV than for the DRV (90 to 180%). It was more efficient when the application time increased but the augmentation of lipids concentration had no effect on it. (3) The cumulated quantity of HpD collected on 10 strips was increased, for each type of liposomes, with higher application times or lipid concentrations. The next experiments will be carried out with another composition of liposomes close to the lipidic skin composition, with human skin and with a model of rat cutaneous tumor.
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