Encapsulation - Microencapsulation

The use of porous membranes to surround transplanted cells (e.g. islets or beta cells)to prevent their rejection. The pore size allows small molecules such as insulin and glucose to pass back and forth maintaining normal function , but does not allows lymphocytes (white blood cells) or large molecules like antibodies to pass thus preventing a rejection attack. Usually the term microencapsulation refers to the individual encasing of islets put in the peritoneal cavity. Macroencapsulation refers to a more complicated devise that consist of a cylinder within a cylinder (chamber) which one end is attached to a vein and the other to an artery. The external cylinder contains the islets, the internal one allows blood to pass. Nutrients contained in the blood come into contact with islets through a common membrane wall .