Continuous Microfluidic Encapsulation of Single Mesenchymal Stem Cells Using Alginate Microgels as Injectable Fillers for Bone Regeneration

Abstract

Encapsulation of single cell in microgels in a biocompatible and scalable manner can enable major advances in applications such as tissue engineering, cell biology, and cell-based therapies. Here, a microfluidics-based approach is developed for continuous encapsulation of mesenchymal stem cells (MSCs) at single-cell level using alginate as the extracellular matrix. This microfluidic technique enables on-chip encapsulation by triggered gelation and direct extraction of cell-laden microgels from oil into aqueous phase, thus retaining the viability and functionality of the loaded cells. Osteogenic culture of MSCs in Ca-alginate microgels show significantly accelerated osteogenesis compared to conventional 2D culture. It is further demonstrated that microfludics-generated alginate microgels can act as delivery vehicles of allogeneic rat MSCs for inducing bone regeneration using the rat tibial ablation model. A significantly higher amount of new bone formation is observed in the bone medullary cavity treated by MSC-laden microgels as relevant to naked MSCs with microgels and empty microgels. To conclude, single cell-laden microgels boost therapeutic effects of bone regeneration compared to conventional cell-based tissue engineering therapy by providing a controlled osteogenic and immune-shielding microenvironment for allogeneic MSCs.