With the rapid increase in number of diabetes patients in the world, there has been an urgent need for a clinically effective diabetes treatment. Islet transplantation is able to replace the impaired islets by implanting normal islets so as to maintain normal blood glucose level, which is recognized as an ideal treatment for diabetes. However, there is a shortage of islet donor resources, and the clinical outcome suffers from a variety of adverse reactions and even cancer risks for long-term use of immunosuppressive agents after transplantation. These challenges have greatly impeded the clinical application of islet transplantation. The applications of bio-derived or synthesized polymers(natural polymers, synthetic polymers, inorganic compounds and other biomaterials) to encapsulate islets enable to create an immune isolation microenvironment. These artificial constructs effectively inhibit immune rejection by avoiding the direct contact between host immune cells and implanted islets. In the application, the islet encapsulation is mandatory to keep the exchange capacity of essential key molecules, such as insulin, glucose and oxygen. This is necessary to ensure the normal physiological activity of transplanted islets and the ability to accurately control blood glucose level. This review summarizes the state-of-the-art of the field of islet encapsulation, including the introduction of the most employed materials, strategies of islet encapsulation, as well as the perspective.
Contents
1 Introduction
2 Advantages of islet encapsulation in islet transplantation
3 Encapsulation materials for islets and islet cells
3.1 Natural polymers
3.2 Synthetic macromolecules
3.3 Inorganic nanomaterials
4 Design strategy of encapsulation of islets and islet cells
4.1 Long-term immune isolation effect
4.2 Transportation of nutrients and oxygen
4.3 Biocompatibility of materials
4.4 Choice of the appropriate transplantation site
4.5 Suppression of the immune response around the graft
5 Conclusion and outlook