DEVELOPMENT AND MECHANICAL EVALUATION OF POLYDIMETHYLSILOXANE-COATED POLYLACTIC ACID MICRONEEDLES AS A POTENTIAL PLATFORM FOR SOLVENT-FREE PARTICULATE DELIVERY

Objectives: Transdermal drug delivery offers a promising alternative to conventional administration methods but remains limited by the stratum corneum’s barrier function. Microneedles (MNs) have emerged as a minimally invasive strategy to overcome this barrier. However, effective attachment and delivery of particulate drugs using polymeric MNs pose fabrication and performance challenges. This study aimed to develop and characterize a novel polylactic acid (PLA) MN system coated with a polydimethylsiloxane (PDMS) layer optimized for enhanced physical adhesion and potential solvent-free attachment of particulate materials. Methods: PLA MN arrays were fabricated using thermal molding with a PDMS mold, followed by ozone treatment to improve surface adhesion. A PDMS40 elastomer layer was uniformly applied and cured to form an adhesive coating. Drug particles were attached by simple pressing. Comprehensive mechanical tests including axial compression, transverse shear, bending resistance, repeated insertion durability, and poke tests were conducted to assess mechanical robustness and functional performance. Base plate tensile, flexural, compressive, and fatigue properties were also evaluated. Results: The PDMS-coated PLA MN showed excellent mechanical strength, with an average axial fracture force of 0.18±0.03 N per needle, providing a safe margin for skin penetration. The MNs exhibited high resistance to bending and shear forces and maintained structural integrity after repeated insertions, with no observed breakage or retention in the skin simulant. Poke tests confirmed >98% insertion efficiency through an 8-layer Parafilm M model with an average penetration depth of ~450 μm. Base plates demonstrated robust tensile (18 megapascals [MPa]), flexural (120 MPa), compressive (15 N), and fatigue resistance, retaining over 95% flexibility after 1,000 cycles. Conclusion: The developed PDMS-coated PLA MNs demonstrated reliable mechanical performance and effective solvent-free particle attachment and delivery. This approach provides a practical and scalable platform for particulate transdermal delivery, paving the way for next-generation, patient-friendly drug delivery systems.