Immobilized microalgal cells as an oxygen supply system for encapsulated pancreatic islets: A feasibility study

Recently, a novel technique for oxygen supply to immunoisolated islets, which adopts the photosynthetic capacity of microalgae to generate oxygen, has been described. Illuminated alga cells, co-immobilized with islets in one compartment, were capable of restoring glucose-stimulated insulin secretion during perifusion with anoxic medium. In the present study, a new model system for photosynthetic oxygen supply to encapsulated islets, containing two separate compartments-one for oxygen-producing alga cells and the other for insulin-secreting pancreatic islets-is described. No insulin response to increasing glucose concentrations was found when encapsulated islets alone were perifused with oxygen-free medium. However, when the perifused chamber contained not only encapsulated islets, but also illuminated algae, immobilized in alginate, the islets showed twice the amount of insulin secretion in response to a high level of glucose (P < 0.01). This finding suggests that the level of photosynthetic oxygen generated in the algal compartment was sufficient to support the functional activity of the islets. Such a technology may offer the potential application for oxygen supply to various transplanted immunoisolated cells.