Composite Dissolving Microneedles for Coordinated Control of Antigen and Adjuvant Delivery Kinetics in Transcutaneous Vaccination

Transcutaneous administration has the potential to improve therapeutics delivery, providing an approach that is safer and more convenient than traditional alternatives, while offering the opportunity for improved therapeutic efficacy through sustained/controlled drug release. To this end, we demonstrate a microneedle materials platform for rapid implantation of controlled-release polymer depots into the cutaneous tissue. Arrays of microneedles comprised of drug-loaded poly(lactide-co-glycolide) (PLGA) microparticles or solid PLGA tips were prepared with a supporting and rapidly water-soluble poly(acrylic acid) (PAA) matrix. Upon application of microneedle patches to the skin of mice, the microneedles perforated the stratum corneum and epidermis. Penetration of the outer skin layers was followed by rapid dissolution of the PAA binder on contact with the interstitial fluid of the epidermis, implanting the microparticles or solid polymer microneedles in the tissue, which were retained following patch removal. These polymer depots remained in the skin for weeks following application and sustained the release of encapsulated cargos for systemic delivery. To show the utility of this approach we demonstrated the ability of these composite microneedle arrays to deliver a subunit vaccine formulation. In comparison to traditional needle-based vaccination, microneedle delivery gave improved cellular immunity and equivalent generation of serum antibodies, suggesting the potential of this approach for vaccine delivery. However, the flexibility of this system should allow for improved therapeutic delivery in a variety of diverse contexts.