Biocompatible fabrication of cell-laden calcium alginate microbeads using microfluidic double flow-focusing device

We employed a microfluidic double emulsion gelation method to generate highly-viable cell encapsulation. Cells encapsulated in sodium alginate droplets were entrapped again in oil droplets to form double emulsions. Through indirect gelation process realized by this double emulsion method, cell-laden alginate microgels were generated to keep cell viability well. Oil droplets could detach spontaneously to further increase the biocompatiblity for encapsulation. [Display omitted] •Microfluidic double emulsion to generate cell encapsulation with high cell viability.•Water-in-oil-in-water (W/O/W) regime to gelate sodium alginate droplets into calcium alginate beads in a mild manner to encapsulate cells.•Oil detached spontaneously from cell-laden microgels to remove the cytotoxic oil.•The influence of flow rates on the size and occupation efficiency of double emulsions was investigated. Cell encapsulation based on droplet microfluidics has been widely adopted in single cell researches, and corresponding highly-uniform cell-laden microgels play significant roles in tissue engineering and cell therapy. However, the encapsulation always faces challenges to maintain favorable cell viability. Herein, based on a double flow-focusing regime, cells were encapsulated in biocompatible sodium alginate droplets, and enveloped in oil droplets to form double emulsions. Ca2+ ions in the outer aqueous phase diffused through the oil and introduced the gelation of sodium alginate to form cell encapsulation. This indirect gelation process and the spontaneous detachment of oil helped to keep cell viability well, which was validated by FDA/PI staining tests.