Material Screening and Fabrication of a Slowly Dissolving Biocompatible Polymeric Microneedle Platform

Abstract

This thesis focuses on identification and characterization of slowly-dissolving, non-cytotoxic and mechanically strong polymeric materials for a microneedle (MN) platform intended for long-term transdermal drug delivery (DD). The study performed systematic material screening on three candidate polymer formulations – polycaprolactone (PCL), chitosan and sodium alginate (SA)-gelatin blend. Three candidates were fabricated through polydimethylsiloxane (PDMS ) micromolding, and assessed for swelling behavior, mechanical performance and cytocompatibility. Experimental results identified PCL as the lead candidate based on swelling tests, where PCL MNs maintained its mass with ±0.4% fluctuations in phosphate-buffered saline (PBS) at 37°C for seven days. SA-gelatin and chitosan MNs exhibited visible fragmentation and major swelling, respectively. Characterization with scanning electron microscopy (SEM) confirmed uniformity of the PCL MN array surface. Mechanical tests with texture analyzer showed that PCL MNs could withstand axial compression forces up to 33 ± 6 N without failure, and achieved 90% ex vivo porcine skin insertion efficiency. Furthermore, cytotoxicity evaluations with PrestoBlue assay demonstrated that all test groups with PCL maintained cell viability of at least 83%. These findings establish PCL MNs as a robust and biocompatible platform for future development of long-term DD systems.