Microneedles for Drug Delivery: Technology and Applications

Transdermal drug delivery offers an alternative to traditional oral and intravenous methods, addressing challenges like poor bioavailability and patient discomfort. However, this approach is limited to molecules with specific physicochemical properties (such as low molecular weight, high potency, and moderate lipophilicity) due to the skin’s stratum corneum barrier. Among various enhancement techniques, microneedle (MN) technology has emerged as a promising solution for delivering therapeutic agents of any size through the transdermal route. Microneedles are micron-sized needles that can perforate the skin's stratum corneum, creating numerous microchannels without penetrating across the dermis, offering a minimally invasive delivery method. MNs are classified into various types, mainly including solid, coated, hollow, dissolving, and hydrogel-forming/swelling microneedles, with the fabrication method depending on the type and material. Microfabrication techniques are currently used to create microneedles, including MEMS-based methods, micromolding, drawing-based methods, and 3D-printing-based methods. In recent years, more and more microneedles have been studied in clinical trials. Although significant progress has been made, ongoing research continues to address the remaining challenges, paving the way for microneedles in future clinical applications.