Structural design strategies of microneedle-based vaccines for transdermal immunity augmentation

As microneedle-based vaccines possess advantages of high compliance, moderate invasiveness and convenience that are highly relevant to their unique design, they are becoming an indispensable piece of the puzzle in the field of medical applications. By selecting appropriate materials and methods convenient for precise control over the structure and morphology, MN-based vaccines with strong mechanical properties and variable forms can be fabricated, and specific biomolecules can be used for monitoring or augmenting human immunity. The structural design strategies of MN-based vaccines are highlighted in this review, following a brief discussion of the mechanism of skin immunity and the classification and fabrication approaches of MNs. The biomedical applications of MN-based vaccines, including sampling from interstitial fluid and therapy in infectious diseases and cancers, have also been demonstrated. Finally, the central challenges in this field and opportunities for future developments are also deliberated.