Closed-loop blood-glucose homeostasis. The power circuit of the metabolic fuel cell constantly monitors the blood-glucose levels and switches on the metabolic fuel cell when blood-glucose levels are above 10 mm. The metabolic fuel cell not only reduces the blood-glucose by glucose consumption but also uses the harnessed energy for electro- or opto-stimulation of rapid vesicular insulin release by engineered human cells. The combination of these actions reduces the blood-glucose to normal levels and the metabolic fuel cell is shut off. As a consequence, electro- and optostimulation ceases, as does the insulin release, providing time for an insulin refill before the next glucose surge occurs. The metabolic fuel cell and the human designer cells form a closed-loop control circuit that maintains blood-glucose homeostasis in an automatic, seamless, and self-sufficient manner.
