Self-setting bioceramic microscopic protrusions for transdermal drug delivery†
Microneedle (MN) technology offers both an efficient and a minimally invasive transdermal drug delivery strategy. The current MNs, made of silicon and metal, have poor biocompatibility and low drug loading, while the polymer MNs have some constraints related to mechanical strength and storage conditions. In this study, self-setting bioceramics were explored as substitutes for the current MN materials for the first time. Self-setting bioceramic microneedles were fabricated using a master mold by a procedure under mild conditions, which could minimize the drug degradation during fabrication and also facilitates a higher drug loading capability than the other current ceramic microneedles. The drug release and mechanical strength were correlated with the microstructure and porosity of the needles. As observed by SEM and microCT, the ceramic paste could fully fill the geometry of the mould and was cured into an array of micro-sized needles. The drug release study showed that the release rate from this type of MN array could be controlled by the bulk surface area, porosity and resorption rate of the ceramic needles. Applying the MNs to porcine skin indicated that the needles were able to pierce the stratum corneum of the skin. We successfully prepared the bioceramic needles that have high mechanical strength and are resorbable, which can promote safe, efficient and successful transdermal drug delivery.