Penetration Profile of Microspheres in Follicular Targeting of Terminal Hair Follicles

The study focused on optimizing the delivery of fluorescent microspheres into hair follicles (HF) to enhance transfollicular administration of drugs, which is beneficial for targeting specific sites within the HF and reducing systemic toxicity. The researchers developed a standardized protocol and tested it on excised skin samples with terminal HF. They found that the optimal size for microspheres to penetrate HF was approximately 1.5 micrometers, achieving a penetration rate of 55% of all HFs and a maximum depth of over 2300 micrometers. Without prior skin treatment using the cyanoacrylate skin surface stripping-technique (CSSS), penetration rates dropped below 27% with a maximum depth of 1000 micrometers. This study established a foundation for follicular targeting, which could potentially reach essential stem cell structures within the HF.