Hyaluronic Acid Microneedles Loaded with Chinese Herbal Extracts as an Intradermal Delivery System for Hair Regeneration

Androgenic alopecia is one of the most common chronic problems for dermatologists worldwide. Some Chinese herbal extracts have been shown to promote hair growth, but the active ingredients are difficult to enter the dermis. Therefore, delivering the active ingredients into the dermis becomes a key factor. Herein, <i>Platycladus orientalis</i> leaf extract (PO-ex) was obtained using ethanol as a solvent, and then hyaluronic acid methacrylate/hyaluronic acid (HAMA/HA) hydrogel was loaded with PO-ex to prepare hyaluronic acid microneedles (PO-ex MN). The double cross-linked HAMA/HA provides sufficient mechanical strength to pierce the stratum corneum and deliver PO-ex into the dermis; PO-ex can effectively improve the environment for hair follicle cell proliferation by removing reactive oxygen free radicals; in addition, the self-repair reaction caused by microneedle mechanical stimulation activates the Wnt/β-catenin pathway associated with trauma repair and promotes hair follicle growth. PO-ex MN is a potential therapeutic strategy for the treatment of androgenic alopecia.