Impact of skin model and dissolvable microneedle design on efficiency of cutaneous protein delivery

Dissolvable microneedle (DMN) patches, or microarray patches (MAP), are drug and vaccine delivery technologies that demonstrate clinical potential due to their ability to enhance thermostability and to permit injection-free, easy administration into the skin. A key attribute for MAP-mediated delivery is maximum delivery efficiency of the vaccine subsequent to administration. Despite an acceptance that not all of the vaccine is delivered, few studies have quantified the delivery efficiency and how the microneedle design impacts on this function. Importantly, there has been no comparative investigation to determine how the source of skin impacts on ex vivo dose delivery. Here, we investigated the amount of protein antigen delivered and microneedle insertion efficiencies to three commonly used skin types: mouse, pig, and human. Pig and human skin performed similarly in skin delivery and insertion efficiency studies. Insertion efficiency in mouse skin was significantly more variable. We also describe how a two-layer DMN patch delivers increased protein delivery to pig skin (88 % ± 8 %) compared to single layer designs (48 % ± 20 %). Overall, our findings indicate that pig skin is a suitable surrogate skin model for human skin, while mouse skin is less representative. These findings will help the development and harmonisation of assays that assess the quality of protein-containing DMN patches.