The Bio-envelope revolution: Encapsulation strategies for stem cell-based therapies

The encapsulation of stem cells within biocompatible biomaterials has revolutionized regenerative medicine by offering a means to enhance cell survival, functionality, and therapeutic efficacy. This strategy creates a protective, semi-permeable microenvironment—often engineered using hydrogels—that closely mimics the native extracellular matrix (ECM) while allowing essential exchange of nutrients, gases, and biochemical signals. Among the most widely studied are mesenchymal stem cells (MSCs), whose multipotent and immunomodulatory properties make them ideal candidates for encapsulated therapies. Encapsulation not only improves MSCs viability and engraftment but also mitigates challenges such as immune rejection and uncontrolled differentiation. A diverse range of natural and synthetic materials—including alginate, collagen, and polyethylene glycol (PEG)—have been developed to fabricate tunable delivery platforms that support cell function and targeted therapeutic action. This review explores the core principles behind cell encapsulation technologies, the pivotal role of hydrogels as ECM analogs, and the clinical advances enabled by these systems. It also addresses current limitations and future directions, including the incorporation of gene-editing tools and stimuli-responsive biomaterials to create intelligent, next-generation cell therapies.