Increased mechanical stability and permeability by filling the interconnected pores of porous microneedles

Abstract A new polymeric microneedle (MN) fabrication technique is described in order to facilitate both higher mechanical stability and continuous drug release capability, a well-recognized challenge in the community. The technique involves filling the pores of a porous MN (PMN) array with a hydrogel. Cellulose acetate (CA) was used to prepare PMN, the interconnected cavity of which was then occupied by a crosslinked poly(N-isopropylacrylamide) hydrogel. Alkali treatment of the PMN array resulted in deacetylation of CA and improved the hydrophilicity on the surface. The hydrogel was readily incorporated by thermal polymerization of the monomers soaked to the PMN array. Mechanical strength tests demonstrated that pore filling enhanced the PMN stability by up to 50%, which was well-above the threshold required for skin penetration. The permeability of the hydrogel remained after pore filling and the drug release rate could be varied by alkali treatment process.