Finite element analysis and optimization of microneedle arrays for transdermal vaccine delivery: comparison of coated and dissolving microneedles

Microneedle arrays have recently been proposed as an alternative device for delivering vaccines into the skin. In recent years, many types of microneedles, such as coated and dissolving microneedles, have been developed with a variety of array configurations. However, the study that alongside compares the vaccine delivery efficiency of different types of microneedles and optimizes their arrangements on an array has been lacking. This study aimed to evaluate the vaccine delivery efficiency of coated and dissolving microneedles as well as to optimize the microneedle arrangements by using a three-dimensional finite element modeling approach. The constructed models describe the antigen release via diffusion, the antigen-receptor binding, and the antigen internalization by antigen-presenting cells (APCs) in the skin layers. Our modeling result reveals that the coated microneedle provides higher efficiency in activating APCs than the dissolving microneedle. It also predicts that the square arrangement of microneedles is not the optimal arrangement. According to the magnitude of APC activation, the acute-angle arrangement of microneedles outperforms the square arrangement by activating more APCs in the dermis.