Assessment of mechanical stability of rapidly separating microneedles for transdermal drug delivery.

The rapidly separating microneedles (RS-PP-MNs), composed of PVA (separable arrow head) MNs and a poly(L-lactide-co-D, L-lactide) (PLA) supporting array, are used for transdermal delivery system at high humidity. The fabricated RS-PP-MNs should have sufficient mechanical strength at different humidity. In general, the water adsorption rate was increased with increasing humidity; by contrast, storage time was decreased with increasing humidity. The higher water adsorption rate indicated the lower mechanical strength, thereby lowering drug delivery efficiency. The prepared RS-PP-MNs could be successfully inserted within the skin at high humid atmosphere due to PLA supporting array. The bright field and fluorescence microscopic images suggested the probable real-time applicability of RS-PP-MNs. The in vitro and in vivo assay suggested that RS-PP-MNs potentially were able to deliver the drugs at high humidity condition. The significant improvement in the drug delivery efficiency and skin penetration ability was observed compared with the traditional MNs. In addition, the fabrication of RS-PP-MNs is facile and scalable. Therefore, the prepared RS-PP-MNs with supporting solid PLA array might be advantageous in real-time applications. This study is of great importance for the MN field as it offers more theoretical support for clinical applications.