A novel two step procedure for immobilizing living cells in microcapsules for improving xenograft survival.

Histologically identified surface irregularities caused by the physical entrapment of encapsulated cells in the microcapsular membrane matrix of standard alginate-polylysine microcapsules potentiated graft rejection in mice. We have therefore devised a novel two step procedure to prevent the entrapment of cells in the capsular membrane matrix. With the new method the capsular membrane appeared uniform and without the physical entrapment of cells in the capsular membrane matrix. Furthermore, after 7 days of intraperitoneal implantation of encapsulated rat hepatocytes in mice, microcapsular membrane perforations and leukocyte infiltrations were not observed. Also a greater percentage of the modified capsules, free from fibrous encapsulation, were recovered after 7 and 11 days of intraperitoneal implantation compared to the standard microcapsule preparations.