To prepare microcapsules with uniform size, the electrospray approach was employed to produce W/W emulsion droplets firstly. An emulsion phase containing 10% (w/v) dextran and 0.3% (w/v) alginate was electrosprayed in air to form droplets, and the emulsion phase was dissolved in the complete H-DMEM medium. The applied voltage was 2.22.4 kV and the distance between the anodic nozzle and cathode was 1.5 mm. The droplets were collected in a petri dish containing 3 ml PEG-rich continuous phase (8% PEG, 0.02% PF-4, and 0.1% pluronic@-127, w/v) and placed at room temperature for 1 h. Then, 3 ml of 0.2% (w/v) CaCl2/8% (w/v) PEG solution was slowly injected into the petri dish. Both of the continuous phase and the CaCl2/PEG solution was dissolved in the normal saline.