Scaffolds for Encapsulation of Stem Cell-Derived ß Cells

Currently, clinical islet transplantation is the most promising minimal invasive therapy to treat the most severe cases of type 1 diabetes, where exogenous insulin administration can no longer be used to control blood glucose levels. Bioengineering approaches through encapsulation of islets can be used to support islets or offer novel implantation sites which could potentially improve the outcome of clinical islet transplantation. However, each bioengineering approach has its advantages and limitations. For instance, shielding islets from the immune system could be realized through the utilization of a barrier strategy, in which immune cells are prevented from entering the islet delivery devices. Nonetheless, this barrier will also impede revascularization of the islets and potentially increase the diffusion distance of oxygen, leading to hypoxic conditions for the encapsulated islets. This chapter covers the main benefits and shortcomings of nano-, micro-, and various macroencapsulation techniques. In general, there is a clear need for evaluation of encapsulation devices in large animal models before translation toward the clinic can be realized. Rodent models often do not translate to the human situation, and successful outcomes in rodent studies do not necessarily guarantee successful clinical outcomes. Finally, commonly used implantation sites and clinical potential of the techniques are also broadly reviewed.