Development of biocompatible alginate capsules for cell therapy

Alginate has become one of the most useful immobilisation materials for living cells. A mixture of alginate and cells solidifies into beads that contain immobilised cells that allow free exchange of proteins, nutrients, and oxygen between the encapsulated cells and the host. The capsules exclude inflammatory cells and protect the encapsulated cells from tissue rejection. Although a range of cells have been suggested for immobilisation, major interest has been devoted to insulin producing cells for the tre atment of Type 1 diabetes and to genetically engineered endostatin-producing cells for the treatment of malignant brain tumors. The major obstacles preventing the use of alginate capsules in vivo have been the capsules' bioincompatibility as well as thei r mechanical instability. The objective of the following proposal is to make stable biocompatible capsules from new enzymatically modified alginates using a family of enzymes, the C-5-epimerases. The capsules will be examined with respect to biocompatibil ity, stability, porosity and gelling properties using established methods as well as confocal AFM- and NMR-imaging. Moreover, we want to examine the use of new stabilising materials for capsule formation. The results should give important information on h ow to construct various alginate capsules to meet the requirements of a particular immobilised system.