ALGINATE POLYLYSINE MICROCAPSULES AS IMMUNE BARRIER - PERMEABILITY OFCYTOKINES AND IMMUNOGLOBULINS OVER THE CAPSULE MEMBRANE

Transplantation of pancreatic islets in alginate polylysine microcapsu les is a potential useful method for treating type I diabetes, In this study, the permeability for alginate-polylysine microcapsules to cyto kines an immunoglobulines has been investigated by a newly developed m ethod. Magnetic monodisperse polymer particles (Dynabeads) coated with antibodies against selected proteins were encapsulated in 0.7 mm algi nate polylysine microcapsules. The capsule membrane permeability to Ig G (150 kDa), Transferrin (81 kDa), Tumor necrosis factor (TNF, 51 kDa) , Interleukin-1 beta (IL-1 beta, 17.5 kDa), and insulin (5.8 kDa) was estimated by measuring the binding of I-125-labeled proteins to the en capsulated antibody coated Dynabeads, Capsules with an inhomogeneous s olid gel core were made of alginates with high guluronic or high mannu ronic acid content and poly-L, (PLL)- or poly-D-lysine (PDL) of concen trations varied from 0.05-0.2%, The various capsules examined were all impermeable to IgG, The capsules made with a PLL-, but not PDL-membra nes were permeable for transferrin, IL-1 beta was found to penetrate a ll of the different capsule types, The high-G capsules, however, could be made impermeable to TNF and still allowed transferrin to pass, The permeability of these capsules to IL-1 beta, but not to TNF was confi rmed in an assay where mouse islets of Langerhans were incubated with TNF and IL-1 beta, and comparing the IL-6 for encapsulated and nonenca psulated islets. (C) 1997 Elsevier Science Inc.