MICRONEEDLE SYSTEMS FOR PAINLESS DRUG AND VACCINE DELIVERY

Abstract

Microneedle (MN) systems are a revolutionary development in transdermal drug and vaccine delivery, as the stratum corneum barrier is overcome through the creation of minimally invasive microchannels (50 -900 µm depth) which do not trigger nerve endings. The technology results in painless delivery of biologics (e.g., insulin, peptides, vaccines) and allows 10-100,000-fold increase in permeability compared with topical formulations. Five different MN types, namely solid, coated, dissolving, hollow and hydrogel-forming, provide different mechanisms: skin pretreatment, rapid release, sustained dissolution, fluid delivery, and controlled swelling, respectively. Lithography (gold standard precision), 3D printing (fast prototyping), and laser cutting are used in fabrication, but cost, scale, and thermal damage are problems. Clinical studies have demonstrated that MNs can be used to administer insulin/peptides with bioavailability of 80-90%, administer thermostable vaccines (e.g., COVID-19 HexaPro, which is stable at 25 °C up to 4 weeks), and cause 300% collagen in anti-aging treatments. Benefits are 60-90 % decreased risk of needlestick injuries, no cold-chain needs, and the possibility of self-administration. Although there are FDA-approved products (e.g., Zosano Qtrypta TM ), there are dose-limits (hollow MNs), insertion inconsistency, and scalability of manufacture. The future perspectives are AI-optimized production, integrated wearable biosensors, and worldwide deliverability of thermostable vaccines.