Human Hair Follicle: Reservoir Function and Selective Targeting

The 2011 document reviews the human hair follicle's role as a reservoir for topical compounds and its potential for selective targeting in drug delivery. It explains how the follicular infundibulum facilitates the penetration of substances due to increased surface area and a disrupted epidermal barrier, which is advantageous for localized treatments with minimal systemic effects. The study of follicle structure and penetration involves techniques like cyanoacrylate skin surface stripping and confocal microscopy. Factors such as molecule size and polarity affect the delivery and retention of compounds in the follicle, with particles that have release mechanisms being preferred. The document also notes the importance of considering the hair follicle's dimensions, sebum content, and growth cycle in designing delivery systems. It emphasizes that active hair follicles allow substance entry, while inactive ones may require mechanical peeling, and that massage can enhance penetration. Further research is needed on the release of drugs from nanoparticles, and the differences between vellus and terminal follicles are significant for topical treatment strategies.