Microfluidic Double Emulsion Gelation Method To Generate Highly Viable Cell Encapsulation

Cell encapsulation based on droplet microfluidics has been widely adopted in single cell researches,and further,the resulting highly-uniform cell-laden microgels play a significant role in tissue engineering and cell therapy.However,the encapsulation methods nowadays face challenges to maintain favorable cell viability.In this work,we demonstrate a microfluidic double emulsion method to generate cell encapsulation with high cell viability.Based on a double flow-focusing regime,cells were at first encapsulated in biocompatible sodium alginate(SA)droplets,and then the oil carrier together with SA droplets were sheared off into droplets by another outer aqueous(OA)phase to form double emulsions.Through adjusting fluidic flow rates,size and occupation efficiency of the double emulsions could be mediated.Ca2+ions in OA phase diffused through the oil and introduced the gelation of SA droplets into calcium alginate(CA)hydrogel beads.This indirect gelation process,together with the spontaneous detachment of oil droplets from CA beads,helped to keep cell viability well,which was validated by FDA/PI staining tests.We believe our method have great potentials for bio-engineering assays based on cell encapsulation,especially those demanding high cell viability.