Controlled release using microencapsulated mammalian cells

Abstract Mammalian cells have been encapsulated in a biocompatible, thermoplastic hydroxyethyl methacrylate-methyl methacrylate copolymer by interfacial precipitation. These microencapsulated cells constitute a novel form of controlled release device in which the therapeutic agent (e.g., insulin, dopamine) is produced by natural or genetically engineered cells which are transplanted into a host, and isolated from the immune system by the permselective capsule wall. Capsules were ~ 900 μm in diameter with an assymmetric, ultrafiltration-like membrane (~90 μm thick). The molecular weight cutoff was ~ 100 kD. Various cells (pancreatic islets, PC12 cells, MLA 144 lymphoma) have been encapsulated. At least some of the cells retain their viability as evidenced by functional assays (insulin or interleukin 2 secretion) or by enzymatic assay. How the capsule wall affects cell behaviour is the focus of current research.