New work from Freie Universität Berlin and the Center of Experimental and Applied Cutaneous Physiology explores how nanogels of a specific size can be designed to penetrate the hair follicle, then release a payload for delivery to viable cells. This research was published online in Nanoscale ahead of print.
According to the Pubmed abstract, nanoparticles of several hundred nanometers can effectively penetrate the hair follicle and may serve as ingredient depots. However, they cannot overcome the hair follicle barrier to reach viable cells or adequately release the loaded drug. On the other hand, small drug molecules cannot penetrate deeply into the hair follicles.
Researchers therefore concluded the most efficient delivery through hair follicles was to employ nanoparticles enabled to release the drug close to the target. Dendritic polyglycerol and N-isopropylacrylamide based thermoresponsive nanogels were the result.
Using confocal laser scanning microscopy, the researchers discovered that, unlike smaller nanogels (< 100 nm), medium and larger-sized nanogels of 300-500 nm penetrated the most effectively, at depths proportional to the nanogel size.
Hair follicles may seem of minor importance for the delivery of actives, since according to Wiechers, "they cover only 0.1% of the total surface area of human skin." However, he adds that "in places where hair density is much higher, such as the face, this local surface area can be much higher—as much as 10%." This, along with the fact that the skin barrier is not as strong in the hair follicle, makes it difficult to ignore this route of entry into the skin.