Microfluidic device for islet conformal coating with a polyethylene glycol-based hydrogel: innovating cell...

Microencapsulation of therapeutic cell clusters within immunoprotective hydrogels is a key strategy in endocrine, hepatic, neural, and musculoskeletal regenerative medicine. Conformal hydrogel coating (CC) of pancreatic islets represents a promising approach for β cell replacement in type 1 diabetes (T1D), offering immunoprotection to prevent rejection. However, current CC techniques are limited by poor scalability, complex workflows, and high reagent use. Here, we present a flow-focusing soft lithographic microfluidic platform that enables thin polyethylene glycol (PEG)-based CC around insulin-secreting cell clusters in a tunable and scalable manner. The device employs three immiscible phases-an aqueous PEG precursor, an oil sheath, and an external cross-linking emulsion-configured to achieve 10-20 μm coating thicknesses. Both murine insulinoma pseudoislets and primary human islets were encapsulated and assessed for coating dimensions, viability, and glucose-stimulated insulin secretion (GSIS). The platform reliably generated CC with thickness independent of cluster size. Fluorescent labeling of PEG coatings and confocal imaging confirmed complete and uniform coverage. Encapsulated clusters retained high viability and GSIS functionality. The system achieved a >10-100-fold reduction in graft volume relative to conventional microencapsulation, potentially expanding implantation site options. The process maintains physiological pH throughout encapsulation, a condition known to support cell health and reduce stress-induced damage. In addition, the streamlined workflow reduces processing time and simplifies operation compared to previous CC approaches. Overall, this work introduces a robust, low-footprint, and adaptable microfluidic strategy for conformal coating of cell clusters, offering a scalable platform for immunoisolated therapeutic cell transplantation in T1D and broader regenerative medicine applications.