Hydrogel-forming microneedles for rapid and efficient skin deposition of controlled release tip-implants

In this work, we introduce, for the first time, novel hybrid microneedle patches with implantable poly(lactic-co-glycolic acid) (PLGA) tips aligned with hydrogel-forming microneedle bases (HFMB) using a dissolvable material. A model dye, Nile red, and an antifungal drug, amphotericin B, were loaded into the PLGA tips in a controlled manner by multiple castings. Three different types of pre-formed microneedle bases including conventional dissolving baseplates (MN0), HFMB with needle heights of 600 μm (MN6) and HFMB with needle heights of 800 μm (MN8) were investigated. Compared to the conventional dissolving baseplate (MN0)-based PLGA tipped implantable microneedle design, the addition of the pre-formed HFMB (MN8) improved in vitro and ex vivo insertion capacities of the patches, increased ex vivo drug delivery efficiency up to 80% of the loaded drug and speeded up the implantation process to within 1 min. An adhesion test indicated that the hydrogel baseplate used in this study was easier to peel off from the skin than the dissolving baseplate. In vitro release studies demonstrated that the release of amphotericin B from the drug loading PLGA tips lasts for a week. Antifungal tests of the inserted amphotericin B loaded PLGA tips revealed their antifungal effects against Candida albicans. The MN8 did not dissolve, leaving no viscous residue but absorbed water and disintegrated after immersion into water. The hybrid PLGA-tipped microneedle system will be ideal for rapid implantation and sustained release of amphotericin B for dermal fungal infections. This hybrid patch design is a novel promising technology for delivering drug-eluting microimplants into the skin while ensuring easy and complete removal of the HFMB. It could have many potential applications in implantable intradermal drug delivery.