Description of the Intrafollicular Delivery of Large Molecular Weight Molecules to Follicles of Human Scalp Skin In Vitro

The study investigated the intrafollicular delivery of large molecules to human scalp follicles in vitro, focusing on the effects of size, charge, and formulation. It was found that cationic lipid-based formulations enhanced the delivery of oligonucleotides within the follicle, directing permeation along the junction of the internal and external root sheath. Lower molecular weight dextrans permeated all follicle components, while higher molecular weight dextrans were confined to areas surrounding the hair shaft. Approximately 0.5% of the applied dose reached the hair bulbs and deeper skin layers within 24 hours. The study concluded that topically applied large molecules, when properly formulated, could achieve pharmacologically active concentrations at the hair bulb.