Modulation of hair growth by topical drug delivery enhanced by STAR particles.

Topical treatments to modulate hair growth are generally limited by low drug bioavailability due to poor skin permeability. Here, we studied the use of STAR particles, which are millimeter-sized ceramic particles with protruding microneedles, to form micropores in the skin to increase skin permeability to hair growth-modulating drugs. STAR particle design and fabrication were optimized, and the resulting STAR particles were shown to reduce lag time and increase skin permeability to minoxidil and acyclovir by more than three-fold compared to no treatment in pig skin ex vivo. In rats, STAR particles also improved topical delivery of minoxidil and acyclovir, which resulted in an increase or a decrease in the number, length and/or thickness of hairs and/or the number of anagen-phase hair follicles after minoxidil or acyclovir treatment, respectively. Clinical exam and histological evaluation showed no evidence of skin irritation or other adverse effects of the treatments. We conclude that STAR particles can increase topical delivery of minoxidil and acyclovir to improve modulation of hair growth promotion and inhibition, respectively.