Optimizing the Capsule-Based Refilling Strategy for an Implantable Insulin Delivery Device Tailored on Human Anatomy

Intraperitoneal insulin delivery using implantable pumps is a promising solution for glycemic control in type-1 diabetes. It results in fast insulin pharmaco-kinetics and pharmaco-dynamics that well mimic human physiological delivery. In the solutions currently available on the market, the refilling procedure is invasive and brings with it complications and discomfort. This study aims to optimize the design of a refilling strategy through ingestible capsules for an implantable insulin delivery system, tailored to human anatomy. We devised a new layout to guarantee a stable and reliable capsule capture. It includes two independent magnetic docking units, based on switch able magnetic circuits, which are sequentially activated to dock a capsule. Finite element simulations were used to assess the docking force exerted on the capsule for different magnet dimensions and capsule-device distances. Bench tests were performed to validate the simulation results and measure the force that the magnetic system has to overcome to guarantee stable docking. The optimized system was included in a mock-up of the device (kidney-shaped, 55 x 30 x 65 mm3) and implanted in an intraperitoneal pouch of two human cadavers (male and female). After the implantation, the attraction force and the capsule-device distance were measured both in- and ex-situ. Results showed that the magnetic force obtained in the in-situ (3.13 ± 1.84 N) and ex-situ (2.78 ± 0.32 N) tests were in good accordance with the simulation results. The system validation on human cadavers confirmed the suitability of the implantation procedure and allowed to identify other important parameters for further development of this technology.