Fabrication of gradient porous microneedle array by modified hot embossing for transdermal drug delivery

A gradient porous microneedle array (GPMA) is developed for transdermal drug delivery. A modified hot embossing approach is proposed to fabricate the GPMA from poly (lactic-co-glycolic acid) powders within a cavity array mold under the coupling combination of gradient thermal and pressure multi-fields. The porosity of the microneedles is a gradient, and the pores are mainly distributed in the tip region. The liquid drug formulation can directly be loaded in the pores of the microneedle tips by dipping. GPMA could penetrate into the rabbit skin without breakage and the penetration force per microneedle is approximately 22 mN. The GPMA can diffuse a dry model drug, namely Rhodamine B, in vitro in the rabbit skin dermis. The GPMA can also effectively deliver an insulin solution in vivo in diabetes rats, lowering the blood glucose levels. Above all, as a dry or liquid drug carrier and a minimally invasive injector, the GPMA offers an effective alternative for transdermal drug delivery.