Composite double-layer microneedle loaded with traditional Chinese medicine for the treatment of androgenic alopecia

Androgenetic alopecia (AGA) is an androgen-mediated alopecia affected by both genes and hormones. Medication is a relatively common treatment. As a new drug delivery method, microneedles (MNs) can effectively break through the stratum corneum barrier, deliver drugs more efficiently, and achieve better therapeutic effects. In this study, we develop a composite double-layer MN through multi-step casting fabrication using a polydimethylsiloxane mold. The needle tip was fabricated by mixed solution of chitosan and polyvinylpyrrolidone which was loaded with Polygonum multiflorum extract, and the base layer was prepared by mixed solution of polyvinyl alcohol and polyvinylpyrrolidone. In vitro mechanical tests showed that the maximum load of a single tip of the drug-loaded MN was about 3.5 ​N, which met the mechanical requirements of skin puncture (>1 ​N). The drug release experiment showed that the MN could achieve gradual drug release. In the animal experiment, pigmentation and hair regrowth occurred earlier in the Polygonum multiflorum-MN (Pm-MN) group than in the other groups, and hair growth finally appeared in almost the entire area. Compared with the AGA model mice, mice in the Pm-MN group achieved an increase in the number and diameter of hair follicles. In conclusion, the Pm-MN is scientific and feasible for treating AGA.