Emerging and Prospective Engineering Technologies Enabling Microneedle Based Vaccine Therapeutics.

Microneedles (MNs) have progressed to a potentially viable method of transdermal vaccination and have accrued immense attention in recent years. By overcoming first-pass metabolism, this emerging technology elicits efficacious therapeutic effects and improved patient compliance. Various technologies and material compositions have been explored to enable drug delivery including solid, coated, dissolving, hollow and hydrogel-forming MNs. In progressive science, there are several emerging engineering techniques that have been used to fabricate MNs for use in drug delivery and aligning therapies, including (not limited to) micromoulding, 3D printing, aerosol jet printing and various electrohydrodynamic strategies. These explorations have yielded promising outcomes in terms of facile MN manufacturing, processing, enhanced mechanical features, applicability (self-administered), portability and therapeutic efficiency. More recently, emerging engineering aspects (e.g. 3D printing, various laser-based techniques and electrospray technology) have been adapted to develop MN vaccine platforms or demonstrate potential in this remit, adding to more established MN vaccine engineering platforms (e.g. micrmoulding). Such developments are viewed as crucial; firstly, to eliminate/reduce the spread of infection as the emergence and occurrence of outbreaks increase, and secondly, to limit the strain on national healthcare systems which rely heavily upon assisted vaccine administration. This review focuses on selected, up-to-date developments and progression of engineering MN technologies/devices into MN vaccine therapeutic platforms. It also embraces specific examples, highlighting applicability and adaptability of existing technologies, with current advances shown and future scope highlighted.