Development and optimization of a dual-photoinitiator, emulsion-based technique for rapid generation of cell-laden hydrogel microspheres

A growing number of clinical trials explore the use of cell-based therapies for the treatment of disease and restoration of damaged tissue; however, limited cell survival and engraftment remains a significant challenge. As the field continues to progress, microencapsulation strategies are proving to be a valuable tool for protecting and supporting these cell therapies while preserving minimally invasive delivery. This work presents a novel, dual-photoinitiator technique for encapsulation of cells within hydrogel microspheres. A desktop vortexer was used to generate an emulsion of poly(ethylene glycol) diacrylate (PEGDA) or PEGDA-based precursor solution in mineral oil. Through an optimized combination of photoinitiators added to both the aqueous and the oil phase, rapid gelation of the suspended polymer droplets was achieved. The photoinitiator combination provided superior cross-linking consistency and greater particle yield, and required lower overall initiator concentrations compared with a single initiator system. When cells were combined with the precursor solution, these benefits translated to excellent microencapsulation yield with 60-80% viability for the tested cell types. It was further shown that the scaffold material could be modified with cell-adhesive peptides to be used as surface-seeded microcarriers, or additionally with enzymatically degradable sequences to support three-dimensional spreading, migration and long-term culture of encapsulated cells. Three cell lines relevant to neural stem cell therapies are demonstrated here, but this technology is adaptable, scalable and easy to implement with standard laboratory equipment, making it a useful tool for advancing the next generation of cell-based therapeutics. (C) 2011 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.