Review article

Glucose sensors: toward closed loop insulin delivery☆

Continuous subcutaneous insulin infusion (CSII) pump is widely considered a convenience and promising way for type 1 diabetes mellitus (T1DM) subjects, who need exogenous insulin infusion. In the standard insulin pump therapy, there are two modes for insulin infusion: basal and bolus insulin. The basal-bolus therapy should be individualized and optimized in order to keep one subject's blood glucose (BG) level within the normal range; however, the optimization procedure is troublesome and it perturb the patients a lot. Therefore, an automatic adjustment method is needed to reduce the burden of the patients, and run-to-run (R2R) control algorithm can be used to handle this significant task.

In this study, two kinds of high order R2R control methods are presented to adjust the basal and bolus insulin simultaneously. For clarity, a second order R2R control algorithm is first derived and studied. Furthermore, considering the differences between weekdays and weekends, a seventh order R2R control algorithm is also proposed and tested.

In order to simulate real situation, the proposed method has been tested with uncertainties on measurement noise, drifts, meal size, meal time and snack. The proposed method can converge even when there are ±60 min random variations in meal timing or ±50% random variations in meal size.

According to the robustness analysis, one can see that the proposed high order R2R has excellent robustness and could be a promising candidate to optimize insulin pump therapy.

Real-time glucose monitoring has been beneficial in reducing health complications associated with diabetes as well as a decrease in mortality. This report describes a novel holographic platform, fabricated via laser ablation on chitosan hydrogel with gold nanoparticles with a replaying in visible and near IR. The sensor responded with a 12 nm and 7 nm shift in wavelength at glucose concentrations in the 0–70 mM range and in the visible and near IR, respectively, at pH 7.4 and an ionic strength of 154 mM. The sensor did not respond to potential interferences found in the interstitial fluid, such as fructose, vitamin C and lactate, at their respective normal concentrations and was stable to fluctuations in temperature, pH and ionic strength. The characteristics of this sensor suggests that it may be applicable for use as an implanted device for the real time monitoring of glucose concentrations in the interstitial fluid using near IR as the interrogating medium.

The DeSyRe project builds on-demand adaptive and reliable Systems-on-Chips (SoCs). As fabrication technology scales down, chips are becoming less reliable, thereby incurring increased power and performance costs for fault tolerance. To make matters worse, power density is becoming a significant limiting factor in SoC design, in general. In the face of such changes in the technological landscape, current solutions for fault tolerance are expected to introduce excessive overheads in future systems. Moreover, attempting to design and manufacture a totally defect-/fault-free system, would impact heavily, even prohibitively, the design, manufacturing, and testing costs, as well as the system performance and power consumption. In this context, DeSyRe delivers a new generation of systems that are reliable by design at well-balanced power, performance, and design costs. In our attempt to reduce the overheads of fault-tolerance, only a small fraction of the chip is built to be fault-free. This fault-free part is then employed to manage the remaining fault-prone resources of the SoC. The DeSyRe framework is applied to two medical systems with high safety requirements (measured using the IEC 61508 functional safety standard) and tight power and performance constraints.

Objective: To outline a roadmap to the artificial pancreas (AP) comprising a subcutaneous (sc) glucose monitor, a control algorithm, and an insulin pump delivering sc insulin.

Research design and methods: A literature review, personal views, and material from the Juvenile Diabetes Research Foundation have been used to prepare the roadmap.

Results: The roadmap identifies sensor reliability but not sensor accuracy as the critical roadblock, which can be addressed by advanced control algorithms combined with safety critical features. It is argued that incremental rather than perfect glucose control should be the objective of the first generation of the AP. Overnight glucose control is more easily achieved than postmeal control and could be the first aim for a commercial AP. Glycated haemoglobin and the risk of hypoglycaemia will remain the primary efficacy and safety measures being accompanied by complementary measures of variability of glucose excursions. Research priorities include the development of AP prototypes incorporating existing glucose monitors with focus on evaluation at home over short- and long-term periods.

Conclusions: The AP promises to revolutionise insulin treatment. Building on technological progress in glucose sensing, the true potential of the AP needs to be assessed by building prototypes and evaluations in home settings.