Trends in drug- and vaccine-based dissolvable microneedle materials and methods of fabrication

Microneedle patches, also called microarray patches (MAP), are an emerging technology for delivery and sampling of drugs, vaccines and other materials. This review focuses on the materials and methods used to fabricate dissolvable microneedles (DMN) for pharmaceutical use. We outline the relative use of excipients, active pharmaceutical ingredients (API) and methods used for DMN fabrication. An extensive search of primary literature, up to April 2021, identified 328 papers under the key terms “dissolvable microneedles” or “polymeric microneedles”. We based the classification of materials on pharmacopoeia definitions. The majority (76%) of the identified publications examined licensed or model therapeutic small molecule drugs. Most reports (58%) focused on drugs or vaccines that are licensed for clinical use. The relative use of excipients with drug-containing compared to vaccine-containing DMN is discussed. Ten polymers and sugars were used for both drug and vaccine DMN. The most frequent methods to produce DMN were casting into moulds using centrifugation or vacuum filling. Novel methods reported include centrifugal lithography and 3D printing. This review provides insight into material selection, the feasibility of production methods at industrial scale and outlines considerations for novel DMN patch fabrication.