Non-invasive delivery of protein and peptide drugs that require frequent administration, such as insulin, is a still standing challenge despite extensive research efforts over the last 50 years. We have recently developed a unique microneedle system, the phase-transition microneedle patch (PTM), which has proven to be a feasible dosage form by pharmacokinetic and efficacy studies using healthy and diabetic pig models. PTM releases its cargo in the skin interstitial fluid by swelling, instead of dissolution o its needle tips, for which skin deposition of the polymeric materials, as seen in dissolvable microneedles, is avoided. The water insoluble microneedles of PTM are comprised of a chemically inert pharmaceutical excipient, polyvinyl alcohol (PVA), formed by a freeze-thaw induced formation of microcrystalline domains as the cross-linking junctions of the needle tip matrix. Proteins and peptides can therefore be safely loaded in microneedle tips without being denatured by the cross-linking reactions, as is true of the chemically cross-linked hydrogel forming microneedles. The ultimate goal of the proposed study is to develop a practical insulin microneedle patch to control the basal blood sugar levels in diabetic patients without pain sensation or skin damage. The specific aims of this study are 1) optimization of the polymer components and fabrication process of PTM to achieve a steady sustained-release of insulin for daily administration; and 2) obtaining pharmacokinetic parameters of the insulin PTM patch in pig models. The animal experiment will be carried out at Rutgers University New Jersey Medical Schools (the collaborator) animal facility according to the institutional guidance for using vertebrate animals.