Bleomycin-Coated Microneedles for Treatment of Warts

Purpose: Bleomycin-coated microneedles were devised for delivery of bleomycin into the sub-epidermal skin layer for the treatment of warts in order to provide patient convenience and reduce patient pain and fear. Method: Poly-lactic-acid (L-PLA) microneedles were fabricated by a molding process and then the tips were partially coated using a dip-coating method based on a microstructure well. The mechanical strength of the pre-coated polymer microneedles was observed by inserting them in porcine foot and back skin. The holes were stained with trypan blue and the mechanical failure of the microneedles was investigated using a scanning electron microscope (SEM). The initial distribution of a model drug using microneedles was compared with distribution by intralesional injection. The amount of drug leaked below the skin using microneedles was measured and compared with that leaked by intralesional injection. The pharmacokinetic properties of bleomycin-coated microneedles were studied. The bleomycin remaining on the coated microneedles after the in vivo pharmacokinetic study was measured. Results: Bleomycin was successfully coated on the tips of L-PLA microneedles. More than 80% of the bleomycin dissolved into the skin in vitro within 15 min. L-PLA microneedles possessed sufficient mechanical strength to penetrate skin with a thick stratum corneum. Compared to intralesional injection, tip-coated microneedles were more effective in distributing a drug into the sub-epidermal skin layer. A pharmacokinetic study of bleomycin-coated microneedles showed 50 min of T_max. Conclusions: Bleomycin-coated microneedles appeared to be a convenient and painless alternative to conventional intralesional injection of bleomycin. The microneedles delivered bleomycin into the targeted dermal layer regardless of body site. Bleomycin-coated microneedles therefore provide a suitable method for the treatment of warts.