Microneedle arrays coated with Middle East respiratory syndrome coronavirus DNA vaccine <i>via</i> electrospray deposition

Microneedle arrays have been shown to be a minimally invasive method of transdermal drug delivery. However, methods to coat these arrays often require a reservoir of the active ingredient, leading to unused and wasted material. Electrospray deposition is a targeted coating method that offers a competitive alternative for coating microneedles. By architecting the charge landscape of the setup, this technology can achieve coating deposition efficiencies nearing 100%, with little to no material wasted during the coating process. A Middle East respiratory syndrome coronavirus DNA vaccine was used as the model material to assess deposition efficiency as well as the efficacy of fragile biological materials subjected to electrospray deposition. Trehalose and polystyrene-<i>block</i>-polyacrylic acid were used as excipients to encourage coating dispersion. These coatings were inserted into Sprague Dawley rats where the antigen was subsequently detected and located using immunohistochemistry. Both coatings, with and without excipients, showed that protein expression is achieved after the vaccine is subjected to electrospray, however, the presence of excipients qualitatively leads to a more disperse diffusion profile. Further, this work demonstrates the capability of electrospray deposition as a highly efficient method to coat microneedles for transdermal drug delivery.