(559d) Design, Structure, Material Strength of Dissolvable Microneedle Patch Vaccine Delivery Systems: From Fabrication to Characterization of Microscale Transdermal Patches

Current advances in microneedle (MN) patch-mediated vaccine delivery make skin a very effective area for application of immune response systems. In many cases, material form, structural strength, failure mode, diffusion and dissolution rate of dissolving MNs depends on structural stability of sugar/polymer formulations. The objectives of this research are to investigate different formulations of sucrose with semi-crystalline polyvinyl alcohol (PVA) or amorphous polyvinylpyrrolidone (PVP) to study structure/processing/properties relationships of MNs, to design MNs through analysis of phenomena on nanoscale in detail using different characterization methods, as well as to systematically examine how the structural stability of sugar/polymer formulations affects material form, structural strength, failure mode, diffusion and dissolution rate of dissolving MNs. It was shown that increase of polymer concentration increases the viscosity as well as the polymer relaxation time, and hence decreases the width of the Newtonian regime. The different formulations showed a variety of chemical interactions when investigated using Fourier transform far infra-red spectroscopy and X-ray radiation diffraction. Nanoindentation provided information on the elastic modulus of single MN formulations. After indentation the MNs were analyzed using SEM to visually assess the failure modes of the MNs. In skin, although PVP had a higher dissolution rate, PVA showed higher mechanical strength compared with PVP.