Penetration and Storage of Particles in Human Skin: Perspectives and Safety Aspects

The document from April 1, 2011, examined the penetration and storage of particles, especially titanium dioxide (TiO₂), in human skin, emphasizing safety and drug delivery. It was discovered that particles approximately 100 nm in size could deeply penetrate and be stored in hair follicles for up to 10 days, which is longer than their retention in the stratum corneum. The study indicated that particle size could be manipulated to target specific follicular structures for drug delivery. It was also found that these particles do not pass through the healthy skin barrier, making them safe for topical use in products like sunscreens. Furthermore, the particles' ability to target follicular structures makes them promising for treating conditions like androgenetic alopecia and acne, as well as for hair growth control. The document concluded that particles larger than 100 nm do not penetrate healthy skin, and research is ongoing for nanoparticles smaller than 100 nm. The potential of hair follicles as a route for drug delivery was emphasized, with particulate carrier systems being advantageous for delivering drugs to specific follicular sites. The release of drugs from nanoparticles at the correct target site is an active area of research, and the study acknowledged financial support from the Foundation “Skin Physiology" of the Donor Association for German Science and Humanities.