Microneedle technologies in emerging strategies for non-transdermal drug delivery

Microneedles (MNs) have been employed in skin drug delivery for over two decades. These platforms have been demonstrating the ability to penetrate restrictive tissue barriers in a minimally invasive manner, which significantly improved the efficiency of transdermal drug administration. More recently, MN technologies have emerged as a versatile platform for drug delivery beyond conventional transdermal applications. Advances in MN engineering have diversified MNs to include unique shapes, materials, and mechanical properties that can be tailored for tissue-specific applications, overcoming limitations of standard delivery methods. This review highlights recent progress in the use of MNs for targeted delivery to ocular, inner ear, gastrointestinal, vascular, buccal, and other internal tissues.