Microencapsulation of Langerhans Islets in Agarose Microbeads and Their Application for a Bioartificial Pancreas

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Abstract
Microencapsulation of islets is considered to be a promising approach to the development of a bioartificial pancreas. In this study agarose was examined as a material to microencapsulate islets. By a low-temperature gelation tech nique, islets can be easily microencapsulated into agarose microbeads without any adverse effect on the functions of islets. Encapsulated islets in agarose microbeads maintained their intact round shapes during the entire period of culturing. They secreted 50-70 μU islet-1 day -1 insulin into the culture medium and regulated insulin secretion minute by minute in response to the change of glucose concentration even after 140 days of in vitro culture. The molecular weight permeability of agarose microbeads can be modulated by changing the agarose concentration. Agarose microbeads containing higher than 10 wt% can hinder the penetration of bovine serum albumin (M.W. = 67,000), and thus can protect islets from the attack of immunoglobulin. Hamster islets encapsulated in microbeads containing 11 wt% agarose were xenogenically transplanted into the peritoneal cavity of a diabetic mouse. Before the transplantation plasma glucose levels were higher than 400 mg dL-1. After transplantation plasma glucose levels were normalized within two days and the normoglycemic period was 29 days. Although more studies are needed to prolong this period for bioartificial pancreas function, agarose is a prominent basic material for en capsulating islets.