Method of containing core material in microcapsules

Abstract

A core material such as animal tissue or cells is contained within a semipermeable vessel which may be a microcapsule, hollow fiber or plastic membrane having a semipermeable wall by a method that prevents the core material from incorporation into the wall of the vessel. This is accomplished by suspending the core material in a solution of polysaccharide gum such as an alkali metal alginate in an amount between about 0.2% and about 0.5%, removing and washing the core material to remove all but a thin layer of polysaccharide gum, and gelling the polysaccharide gum with multivalent cations or other means to form a pretreated core material. The pretreated core material is contained within a semipermeable vessel such as by suspending the pretreated core material in a solution of alkali metal alginate, forming the suspension into droplets, gelling the droplets to form temporary shape-retaining capsules and treating the capsules with a polymeric material having groups that react with and crosslink acid groups of the capsules to form a permanent semipermeable membrane around the capsules. A second permanent semipermeable membrane may be formed around the capsules to form double-walled microcapsules by further treating the capsules with the polymeric material. The semipermeable vessel may be impermeable to immune factors. Cells or tissue can be transplanted from a donor to a subject such as by using pancreatic islet tissue or cells as the core material of the double-walled microcapsules and transplanting the microcapsules by intraperitoneal injection into a diabetic subject.