Figure 7.

(A) Profile of blood glucose and insulin concentration with high-starch and high-sucrose diets. (B) Schematic illustrating the concept of closed-loop insulin delivery for the management of blood glucose levels in Type 1 diabetes patients. (C) Comparison of the time for a molecule with assumed D=1×10^-6 cm²/s to diffuse a distance within a material with milliliter to nanometer sizes (top) and a scanning electron microscopic image of nanohydrogel particles in a composite membrane (bottom). (D) Schematic of a chemically-driven closed-loop insulin delivery device based on glucose oxidase, pH-responsive nanogel, catalase and MnO₂ NPs. Glucose oxidase catalyzes the oxidation of environmental glucose to gluconic acid, which induces shrinkage of embedded pH-sensitive nanogels, leading to increased membrane porosity and faster diffusive release of insulin from the device. Catalase and MnO₂ nanoparticles remove by-product H₂O₂ and regenerate O₂, which is required for glucose oxidation. (E) Blood glucose levels of healthy (square) and diabetic rats implanted with the closed-loop insulin delivery device (circle) over a 90 min period following a bolus injection of glucose. Error bars represent SD (n=3). The implanted devices enabled blood glucose levels to return to a normal range within ∼30 min after glucose injection, thus mimicking the physiological insulin response of healthy rats. The figures are reproduced from Daly et al¹⁶⁰, Gordijo et al¹⁷², Li et al¹⁶⁹ and Chu et al¹⁷¹ with permission.