Review of Advanced Hydrogel-Based Cell Encapsulation Systems for Insulin Delivery in Type 1 Diabetes Mellitus

Type 1 Diabetes Mellitus (T1DM) is characterized by the autoimmune destruction of beta-cells in the pancreatic islets. In this regard, islet transplantation aims for the replacement of the damaged beta-cells through minimally invasive surgical procedures, thereby being the most suitable strategy to cure T1DM. Unfortunately, this procedure still has limitations for its widespread clinical application, including the need for long-term immunosuppression, the lack of pancreas donors and the loss of a large percentage of islets after transplantation. To overcome the aforementioned issues, islets can be encapsulated within hydrogel-like biomaterials to diminish the loss of islets, to protect the islets resulting in a reduction or elimination of immunosuppression and to enable the use of other insulin-producing cell sources. This review aims to provide an update on the different hydrogel-based encapsulation strategies of insulin-producing cells, highlighting the advantages and drawbacks for a successful clinical application. Authors thank the support to research on cell microencapsulation from the University of the Basque Country UPV/EHU (EHUa16/06 to L.SB) and the Basque Country Government (Grupos Consolidados, ref. no.: IT907-16 to J.L. P). Authors also thank ICTS "NANBIOSIS", specifically by the Drug Formulation Unit (U10) of the CIBER in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN) at the University of Basque Country UPV/EHU in Vitoria-Gasteiz.