3D micro-nano printing technology as a transformative tool apply for microneedle drug delivery

Microneedles (MNs) penetrate the stratum corneum and reach the epidermis, bypassing nerve fibers and providing a precise and controlling pathway for the delivery small molecule drugs, proteins, and nucleic acid drugs. This approach minimizes pain and tissue damage during penetration, facilitating autonomous administration. Emerging 3D micro-nano printing technologies offer innovative fabrication strategies for MNs. In addition to enhanced printing resolution, 3D printing allows flexibility in prototype design and manufacturing methods, enabling the fabrication of complex structure MNs or polydimethylsiloxane (PDMS) molds with excellent repeatability and effectiveness. Recently, several micro-nanoscale 3D printing technologies, such as projection micro stereolithography (PμSL) and two-photon polymerization (TPP), have been integrated into various stages of MNs manufacturing. This review aims to provide a comprehensive overview of diverse strategies for drug release and delivery modes using MNs, and a specific focus on analyzing advancements in 3D micro-nano printing technologies. It emphasizes the pivotal role played by 3D printing in the field of MNs and specifically discusses future research directions and emerging trends in this domain.