Transdermal delivery of insulin across human skin in vitro with 3D printed hollow microneedles

In the current study hollow microneedles (HMNs) were fabricated by means of vat polymerization method for the transdermal delivery of insulin. Two geometries of HMNs were designed in a Computer Aided Design (CAD) software namely, curved pyramid and syringe-like and fabricated with Liquid Crystal Display (LCD) method. Dimensions were determined and quality features were imaged with scanning electron microscopy (SEM). Volumetric characterization of HMNs and microchannels was performed by microfocus computed tomography (μCT) whereas mechanical characterization and skin penetration tests of the two geometries were carried out both experimentally and by Finite Element Analysis (FEA) simulation. Diffusion studies of insulin across full thickness human skin were performed in vitro using Franz diffusion cells. Insulin samples were analyzed with liquid chromatography-mass spectrometry (LC-MS). The results show that the transport might be affected by the shape of the microneedles.