Oxygen supply is expected to be one of major limiting factors that determine survival of islets in microcapsules after transplantation. Fick's law is applied to derive equations describing the oxygen pressure (PO_2) profiles. The PO_2 profiles calculated demonstrate that the thickness of the microcapsule membrane does not significantly affect oxygen supply to the islet. On the other hand, it drastically decreases as the fibrous tissue surrounding the microcapsule becomes thicker. The islet will be destroyed non-immunologically by limiting oxygen supply, when the microencapsulated islets are surrounded by the thick fibrous tissue.
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