Challenges and strategies in developing microneedle patches for transdermal delivery of protein and peptide therapeutics.

The birth of microneedles, an array of needles sufficiently long to penetrate epidermis but small enough to do not cause skin injury and pain feeling, has offered a highly promising solution for non-invasive delivery of protein and peptide drugs, a long-cherished desire over eighty years. However, the attempts to develop clinically feasible microneedle transdermal delivery methods encountered series of difficulties, for which a decade research efforts have yet to result in a single product. Microneedles may be incorporated into devices as skin pre-treatment tools, skin microinjectors as well as transdermal patches by their functions in drug delivery. They may also be categorized to insoluble solid microneedles, hollow microneedles, soluble/degradable solid microneedles and phase-transition microneedles by their structure and forming materials. This review article is aimed to update the progress and discuss the technical challenges raised in developing protein/peptide loaded microneedle patches.