Penetration and Distribution of Three Lipophilic Probes in Human Skin Focusing on the Hair Follicle

In a study from 2002, researchers investigated the penetration and distribution of three fluorescent lipophilic probes (Oregon Green® 488, Bodipy® FL C5, and Bodipy® 564/570 C5) in human scalp skin using confocal laser scanning microscopy. After an 18-hour penetration period, the skin was imaged, and relative accumulation values were calculated. The findings showed that Bodipy® FL C5, with medium lipophilicity, had the highest overall penetration, while Bodipy® 564/570 C5, with high lipophilicity, had the lowest penetration but the highest relative accumulation within the hair follicle. Additionally, adding 30% ethanol to the donor phase increased follicular delivery for the substance with low lipophilicity. The study concluded that drug delivery to hair follicles can be enhanced by increasing the lipophilicity of the drug and optimizing the donor phase composition, but the specific transport route to the follicles remains unclear. The number of human subjects or skin samples used in the study was not specified.