Recent Advances in Microneedle Technology for Transdermal Drug Delivery: A Comprehensive Review

Transdermal drug delivery is an attractive alternative to oral and parenteral administration due to its non-invasive nature, improved patient compliance, and avoidance of first-pass metabolism. However, the stratum corneum presents a major barrier to the transdermal transport of hydrophilic and macromolecular drugs. Microneedle (MN) technology has emerged as a promising approach to overcome this limitation by creating transient microchannels in the skin with minimal pain and tissue damage. Microneedles are micron-scale needle arrays capable of delivering a wide range of therapeutic agents, including small molecules, peptides, proteins, vaccines, and nucleic acids. This article reviews the principles of transdermal drug delivery using microneedles, with emphasis on types of microneedles (solid, coated, dissolving, hollow, hydrogel-forming, and porous), materials used, fabrication techniques, and mechanisms of drug transport. Recent advances in microneedle fabrication methods such as microelectromechanical systems (MEMS), micromolding, laser micromachining, and additive manufacturing are discussed. The clinical and therapeutic applications of microneedles in diabetes management, vaccination, cancer therapy, and delivery of biopharmaceuticals are highlighted. Despite challenges related to drug loading capacity, mechanical strength, manufacturing scalability, and regulatory approval, microneedle-based systems represent a versatile and promising platform for next-generation transdermal drug delivery.