Integrated electronic/fluidic microneedle system for glucose sensing and insulin delivery

Background: Precise and dynamic blood glucose regulation is paramount for both diagnosing and managing diabetes. Continuous glucose monitoring (CGM) coupled with insulin pumps forms an artificial pancreas, enabling closed-loop control of blood glucose levels. Indeed, this integration necessitates advanced micro-nano fabrication techniques to miniaturize and combine sensing and delivery modules on a single electrode. While microneedle technology can mitigate discomfort, concerns remain regarding infection risk and potential sensitivity limitations due to their short needle length. Methods: This study presents the development of an integrated electronic/fluidic microneedle patch (IEFMN) designed for both glucose sensing and insulin delivery. The use of minimally invasive microneedles mitigates nerve contact and reduces infection risks. The incorporation of wired enzymes addresses the issue of "oxygen deprivation" during glucose detection by decreasing the reliance on oxygen. The glucose-sensing electrodes employ wired enzyme functionalization to achieve lower operating voltages and enhanced resilience to sensor interference. The hollow microneedles' inner channel facilitates precise drug delivery for blood glucose regulation. Results: Our IEFMN-based system demonstrated high sensitivity, selectivity, and a wide response range in glucose detection at relatively low voltages. This effectively reduced interference from both external and internal active substances. The microneedle array ensured painless and minimally invasive skin penetration, while wired enzyme functionalization not only lowered sensing potential but also improved glucose detection accuracy. In vivo, experiments conducted in rats showed that the device could track subcutaneous glucose fluctuations in real-time and deliver insulin to regulate blood glucose levels. Conclusions: Our work suggests that the IEFMN-based system, developed for glucose sensing and insulin delivery, exhibits good performance during in vivo glucose detection and drug delivery. It holds the potential to contribute to real-time, intelligent, and controllable diabetes management.

Avoiding Potential Pitfalls in Designing Wired Glucose Biosensors

Glucose sensing has been studied for more than half a century, leading many to believe that further progress comes mainly from engineering efforts. Our society requires robust, reliable, compact, and easy-to-use sensing solutions for decentralized applications such as wearables, and engineering solutions are essential. However, true progress is only possible by understanding and improving the underlying working principles and fundamental limitations. This Perspective discusses the delicate relationship between the observed current and glucose concentration when using wired enzyme biosensors. Some of the potential pitfalls often encountered in the recent literature are discussed. These include the need to suppress the influence of enzyme turnover kinetics on the sensor signal and the undesired faradaic charging of the electron transfer mediator that gives a continuously decaying baseline signal. These fundamental issues must be carefully evaluated and resolved for the realization of continuously operating enzyme biosensor systems.