Overcoming Hypoxia: Review of the Encapsulation System to Increase Survival and Viability of Stem Cells

Abstract

Islet encapsulation technologies aim to protect insulin-producing cells from immune attack while supporting their metabolic function. Two main strategies are currently pursued: microencapsulation and macroencapsulation. Microencapsulation offers a favorable surface to volume ratio, allowing sufficient nutrient and oxygen diffusion to individual or clustered islets. In contrast, macroencapsulation systems enclose larger cell masses within a single device, simplifying retrieval but creating pronounced diffusion limitations, particularly for oxygen. These hypoxic conditions often lead to central necrosis and loss of islet function. To overcome this, various oxygen delivery strategies have been explored, including oxygen-generating materials and external oxygen refueling chambers. However, many of these approaches are limited by uncontrolled release kinetics, cytotoxic byproducts, and poor longterm stability. Perfluorocarbons (PFCs) offer an elegant alternative. These synthetic compounds can physically dissolve and gradually release oxygen in response to local gradients, without generating reactive intermediates. Their compatibility with encapsulation matrices and potential for repeated oxygen loading make them ideal candidates for improving islet survival, especially in macroencapsulation formats. This review highlights current advances in encapsulation technology, compares oxygenation strategies, and explores the potential of PFCs to overcome one of the most persistent barriers in islet transplantation: the challenge of maintaining viability in oxygen-restricted enviroments.