3D printed hollow microneedles for transdermal insulin delivery

Microneedles (MN) are miniature devices of a maximum length of 1000 μm, capable of perforating painlessly stratum corneum and releasing their active content in the skin layers beneath. The significance of MNs lies on the fact that they have the potential to substitute the fear inducing injections, while avoiding first pass effect or other possibly unwished metabolic changes of the oral administration1. In the current study 3D printed microneedles were fabricated by means of liquid crystal display (LCD) vat polymerization 3D printing technology for the transdermal delivery of human insulin in vitro.In the current study the structural features of two different 3D printed 6x6 HMN geometries were assessed. Non-destructive 3D (volumetric) imaging by means of μCT demonstrated that the 3D printing method used in this study allows for high consistency and reproducibility with respect to needles’ geometric characteristics. Diffusion studies demonstrated that syringe-like HMNs were more effective upon insulin administration compared with curved pyramid ones. Although syringe-like geometry penetrates skin at higher insertion force, it is probably more suitable for macromolecular drug delivery which might be attributed to the geometrical characteristics of the microneedles