In this study, polymeric microneedle patches were fabricated by stereolithography, a 3D printing technique, for the transdermal delivery of insulin. A biocompatible resin was photopolymerized to build pyramid and cone microneedle designs followed by inkjet print coating of insulin formulations. Trehalose, mannitol and xylitol were used as drug carriers with the aim to preserve insulin integrity and stability but also to facilitate rapid release rates. Circular dichroism and Raman analysis demonstrated that all carriers maintained the native form of insulin, with xylitol presenting the best performance. Franz cell release studies were used for in vitro determination of insulin release rates in porcine skin. Insulin was released rapidly within 30 min irrespectively of the microneedle design. 3D printing was proved an effective technology for the fabrication of biocompatible and scalable microneedle patches.

3D printed microneedle arrays were fabricated using a biocompatible resin through stereolithography (SLA) for transdermal insulin delivery. Microneedles were built by polymerising consecutive layers of a photopolymer resin. Thin layers of insulin and sugar alcohol or disaccharide carriers were formed on the needle surface by inkjet printing. The optimization of the printing process resulted in superior skin penetration capacity of the 3D printed microneedles compared to metal arrays with minimum applied forces varying within the range of 2 to 5N. Micro-CT analysis showed strong adhesion of the coated films on the microneedle surface even after penetration to the skin. In vivo animal trials revealed fast insulin action with excellent hypoglycaemia control and lower glucose levels achieved within 60 min, combined with steady state plasma glucose over 4 h compared to subcutaneous injections.

3D printing has emerged as a powerful manufacturing technology and has attracted significant attention for the fabrication of microneedle (MN)-mediated transdermal systems. In this work, we describe an optimisation strategy for 3D-printed MNs, ranging from the design to the drug delivery stage. The key relationships between design and manufacturing parameters and quality and performance are systematically explored. The printing and post-printing set parameters were found to influence quality and material mechanical properties, respectively. It was demonstrated that the MN geometry affected piercing behaviour, fracture, and coating morphology. The delivery of insulin in porcine skin by inkjet-coated MNs was shown to be influenced by MN design.