Microencapsulation of living tissue and cells

Claim 1

A microcapsule having a diameter of about 500 to about 2000 μm and suitable for implantation into an animal body, comprising: a core comprising one or more viable, healthy, physiologically-active tissue cells capable of ongoing metabolism, and a biocompatible semi-permeable membrane surrounding and enclosing said core, said semi-permeable membrane being permeable to tissue nutrients and metabolic products produced by the tissue but impermeable to immune system proteins, said semi-permeable membrane having a molecular weight cut-off of below about 150,000 daltons, said biocompatible membrane being a hydrogel formed by ionic reaction between a polylysine polymer having a molecular weight from about 10,000 to about 30,000 daltons and a polymeric material bearing negatively-charged groups to provide an outer negatively-charged surface, said polylysine polymer membrane having a durability sufficient to permit said microcapsules to be injected in the animal body and sufficient to maintain said microcapsules in an intact form and to permit said tissue to effect ongoing metabolism when injected into the animal body for a period of time exceeding three months.

Claim 11

A method of encapsulating a core material within a semi-permeable membrane to form microcapsules for implantation into an animal body, which comprises: (a) placing the material in an aqueous solution of a water-soluble polymeric substance that can be reversibly gelled and which has free acid groups, (b) forming the solution into droplets, (c) gelling the droplets to produce discrete shape-retaining temporary capsules, (d) forming semi-permeable membranes about the temporary capsules by contact between the temporary capsules and a polymer containing free amino groups to cause ionic reaction with the acid groups in a surface layer of the capsule, said polymer containing free amino groups being polylysine having a molecular weight of about 10,000 to about 30,000 daltons, said contact being effected for a period of time no less than about four minutes sufficient to provide a polymer coating on the temporary capsule of sufficient durability to permit the microcapsules to be injected into the animal body, and (e) contacting said microcapsules formed in step (d) with a biocompatible polymeric material which contains free negatively-charged groups capable of ionic reaction with the free amino groups in a surface layer of the microcapsule, thereby to form an outer coating of said biocompatible polymeric material on said microcapsules.

Claim 12

A method of encapsulating a core material within a semi-permeable membrane to form microcapsules for implantation into an animal body, which comprises: (a) placing the material in an aqueous solution of a water-soluble polymeric substance that can be reversibly gelled and which has free acid groups, (b) forming the solution into droplets, (c) gelling the droplets to produce discrete shape-retaining temporary capsules, (d) forming semi-permeable membranes about the temporary capsules by contact between the temporary capsules and a polymer containing free amino groups to cause ionic reaction with the acid groups in a surface layer of the capsule, said polymer containing free amino groups being polylysine having a molecular weight of about 10,000 to about 30,000 daltons, said contact being effected for a period of time no less than about four minutes sufficient to provide a polymer coating on the temporary capsule of sufficient durability to permit the microcapsules to be injected into the animal body, and (e) contacting said microcapsules formed in step (d) with a biocompatible polymeric material which contains free negatively-charged groups capable of ionic reaction with the free amino groups in a surface layer of the microcapsule, thereby to form an outer coating of said biocompatible polymeric material on said microcapsules.