Basic study in artificial pancreas using encapsulated islets as blood glucose measurement and control system

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Artificial pancreas (artificial βcell) is divided into two categories, namely mechanical artificial pancreas which uses mechanical insulin infusion pump, and bio-artificial (hybrid) pancreas using encapsulated islets of Langerhans. Mechanical artificial pancreas is subdivided into a closed loop control system that uses glucose sensing system and an open loop system that does not use glucose sensing system. In case of mechanical artificial pancreas, open loop control system that infuses insulin according to pre-programmed pattern without glucose sensing does not provide good control of blood glucose level. Although the closed loop system can control blood glucose level well by infusing appropriate amount of insulin based on the measurement of the patient's glucose level, the longevity of the currently available implantable glucose sensor limits the duration of continuous usage. Also the drift of the sensor might lead to the deterioration of control quality. On the other hand, bio-artificial (hybrid) pancreas uses living islet of Langerhans harvested from an animal such as pig for control and measurement of blood glucose level of a patient. However, in order to apply this method to human, amount of required islet is very large. The accumulation of implanted encapsulated islet in body might do harm in long term application. In this study, we proposed a novel artificial pancreas where open loop mechanical artificial pancreas provides most of the insulin required in accordance with the pre-programmed pattern and encapsulated islet of Langerhans function as a measurement and control system for the remaining errors that cannot be controlled by the open loop system. The feasibility of this new system was confirmed by computer simulation study and preliminary animal experiment.