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A Cappai

Publications and source records attributed to A Cappai.

6 recordsLinked to original sources
PubMed1995

Evaluation of new small barium alginate microcapsules.

Microencapsulation of islets of Langerhans has been proposed in order to prevent immune rejection and possible recurrence of autoimmune disease. This study introduces a fast simple one-step microencapsulation procedure which allows the production of small sized barium-alginate beads. The volume of the microcapsules produced was approximately that of the encapsulated islets. Consequently, the insulin kinetics and the oxygen diffusion were favoured, while the transplanted tissue volume was reduced. Electron microscopy and immunoisolating testing were performed to evaluate the molecular cut-off, the physical and chemical characteristics of these microcapsules. Immunohistochemical staining and perifusion experiments of microencapsulated pancreatic islets showed their viability after the encapsulation procedure as well as in vivo experiments. In fact, microencapsulated porcine islets were implanted intraperitoneally into streptozotocin-diabetic rats. The xenografts reversed the hyperglycemic state and functioned for a period ranging from 9 to 385 days. The low mannuronic acid concentration and the purity grade of the alginate, exerted a combined influence on the capsule biocompatibility as in vivo studies showed.

Alginates↗
PubMedDate not supplied

[Xenograft of pancreatic islets: preliminary results of a new immunoisolation method].

Results of clinical islet transplantation remain disappointing despite the advances in islet technology. Availability of human organs and control of rejection by adequate immunosuppressive therapy remain the unsolved problems. Transplantation of xenogeneic tissue enclosed in immuno-separating membranes without immunosuppressive drugs may be a solution. In the present study porcine pancreatic islets were isolated by semiautomated method and purified utilizing discontinuous Euroficoll gradients on IBM 2991 cell separator. The porcine pancreatic islets were encapsulated with a new one-step method utilizing a home-made droplet generator. Each microcapsule contained one or two islets and microcapsule diameter was approximately that of the islets. This condition allows an optimal diffusion of insulin, glucose, nutrients and oxygen. Consequently, perifusion experiments with encapsulated porcine islets revealed a typical biphasic pattern of insulin release as it was seen in unencapsulated controls. Human erythrocytes were encapsulated and incubated with serum containing hemolysins and complement. These experiments showed that the encapsulated erythrocytes were protected against the hemolytic activity of Ig G and complement fractions. In conclusion, this encapsulation procedure allows the production of a very thin barium alginate membrane around the islets with very little increase of the total volume of transplanted tissue.

Animals↗