An Insulin Microneedle Pen (IMP) for Self-Subcutaneous Insulin Injection

Metallic hollow microneedles (MHMs) are an ideal alternative to traditional insulin pen needles for innocuous self-administration of insulin into the subcutaneous layer. Nonetheless, MHMs present a number of challenges, including restricted use of biocompatible materials, biohazard issues, and limitations of scale-up fabrication. Here, a novel MHM-manufacturing technology that creates a high-aspect-ratio microstructure by simple centrifugation is proposed. Instead of thermoplastics, biocompatible polyvinylpyrrolidone (PVP) is used without any biohazardous solvent. The critical hurdle—maintaining the geometric integrity of the water-soluble PVP microneedle mold during electroplating—is overcome via a waterproof parylene coating. Cost-effective nickel-carbon tungsten electroless plating is performed that is suitable for clinical application. For the first time, this MHM is assembled into an insulin pen system for manufacture of an insulin microneedle pen (IMP). Characteristics of the IMP are optimized: length: 8 mm, minimized outer diameter: 125 µm, and a sharp bevel angle: 15°. It is demonstrated that the IMP not only administers insulin with the same accuracy as a traditional insulin pen needle but also produces less tissue damage in a porcine model. The proposed IMP may facilitate clinical application and potentially make the daily treatments necessary and easier for patients with diabetes.