Advances in alginate encapsulation of pancreatic islets for immunoprotection in type 1 diabetes

Background: Islet transplantation is a promising minimally invasive approach that dispenses with many challenges, especially immunological complications such as instant blood-mediated inflammatory reaction, autoimmunity, and allogeneic or xenogeneic rejection. Besides, scare of islet donor, side effects of immunosuppressant, and poor angiogenesis are also crucial factors for long-term islet survival and function. Approaches to the encapsulation of islets have been introduced to address aforementioned challenges. Area covered: In this review, we summarize the concept of islet encapsulation using alginate to minimize the immunological complications, maintain islet morphology, and exchange of nutrients, hormones, and metabolic waste via isolating pancreatic islets from host immune cells. Alginate encapsulation technologies like dripping, microfluidics, and 3D printing are also briefly introduced. Similarly, this review outlines islet encapsulation strategies (co-encapsulation with other cells, peptides, drugs, etc.,) and approaches (nano-, micro-, and macroencapsulation) using alginate. Alongside this, this review introduces the use of alginate in an oxygenation system to overcome the hypoxic environment faced by encapsulated islets. Finally, challenges and opportunities for islet encapsulation using alginate are also discussed in terms of clinical applications. Expert opinion: With the aim of immunoisolation, islet encapsulation using alginate reduces immunological attacks and enhances the survivability of islets after transplantation. Alginate shows promise based on its biocompatibility, non-toxicity, and easy and fast gelation under physiological conditions. Intriguingly, it can also co-encapsulate islets with other biomolecules and shows compatibility with other polymers. With ongoing strides in research on islet encapsulation, alginate-encapsulated islets could be available for the treatment of type 1 diabetes in the near future.