Advanced transdermal drug delivery system: A comprehensive review of microneedle technologies, novel designs, diverse applications, and critical challenges

Abstract

Transdermal drug delivery presents numerous advantages over conventional administration routes, including non-invasiveness, enhanced patient adherence, circumvention of hepatic first-pass metabolism, self-administration capabilities, controlled release, and increased bioavailability. Nevertheless, the barrier function of stratum corneum limits this strategy to molecules possessing requisite physicochemical attributes. To expand the field of transdermal delivery, researchers have pioneered physical enhancement techniques, with micron-sized needles emerging as a particularly promising platform for the transdermal and intradermal delivery of therapeutic agents across a spectrum of molecular sizes. Microneedles function by disrupting the skin's integrity, generating microchannels that facilitate efficient drug permeation. This innovative technology boasts a captivating profile characterized by non-invasive drug delivery, enhanced efficacy and onset time, improved patient acceptability, self-administration possibilities, and precise dosing capabilities. Consequently, both academic institutions and industry have invested substantial resources in the development of microneedle systems for pharmaceutical delivery. This comprehensive review elucidates the multifaceted aspects of microneedle technology, encompassing its historical evolution, diverse materials, innovative designs, fabrication methodologies, and characterization techniques. The review extends to various microneedle types, including solid, hollow, coated, dissolving, swelling, and porous microneedles, as well as cutting-edge designs such as stimulus-responsive, iontophoresis-assisted, and bionic microneedles. Furthermore, we explore microneedle applications in vaccination, targeted delivery, and the administration of biologics, long-acting therapeutic agents, and cosmetics. Critical challenges in microneedle development, including dimensional considerations, safety concerns, acceptability factors, production scalability, regulatory hurdles, and sustainability issues, are thoroughly addressed, alongside a presentation of future prospects in this rapidly evolving field.

Keywords: Applications; Challenges; Classifications; Designs; Microneedles; Transdermal delivery.