Engineering Immune‐Protective Stem Cell‐Derived β‐Cell Grafts for Type 1 Diabetes: Encapsulation Technologies and the Emerging Graft Ecosystem

BACKGROUND: Stem cell-derived β-cell replacement has emerged as a promising strategy for the treatment of type 1 diabetes (T1D), potentially addressing the limitations of exogenous insulin therapy and donor-dependent islet transplantation. However, despite substantial progress in stem cell differentiation and transplantation technologies, long-term graft survival remains constrained by immune rejection, recurrent autoimmunity, fibrosis, hypoxia, and inadequate vascularization. Encapsulation technologies have therefore become central to the development of clinically viable bioartificial pancreas systems. METHODS: This review examines advances in stem cell-derived β-cell replacement, with particular emphasis on encapsulation technologies and their translational challenges. Major stem cell sources, including embryonic stem cells and induced pluripotent stem cells, contemporary differentiation strategies, and clinical progress were evaluated. Microencapsulation, macroencapsulation, and conformal coating approaches were critically considered with respect to immunoprotection, mass transport, retrievability, and long-term graft functionality. Biological barriers and emerging engineering strategies were further integrated within a unified mechanistic framework. RESULTS: Current evidence indicates that successful long-term β-cell replacement is limited not only by immune-mediated injury but also by foreign body responses, pericapsular fibrosis, hypoxia, inadequate vascular integration, and compromised mass transport. Emerging approaches, including oxygen-generating biomaterials, immunomodulatory encapsulation systems, vascularization-promoting platforms, smart responsive biomaterials, and gene-edited hypoimmune β-cells, are being developed to overcome these barriers. Collectively, these advances indicate that durable graft function requires coordinated regulation of immunity, oxygenation, vascularization, and tissue homeostasis rather than the generation of functional insulin-producing cells alone. CONCLUSIONS: Durable β-cell replacement for T1D will likely require engineering a supportive graft ecosystem rather than focusing exclusively on cell replacement. The field is consequently transitioning from cell replacement engineering toward graft ecosystem engineering, in which stem-cell engineering, biomaterials science, immune modulation, vascularization strategies, and biosensing technologies are integrated to create clinically scalable and durable therapeutic platforms.