“…PSF beads (Sigma-Aldrich, Taipei, Taiwan) and polyethylene glycol (Sigma-Aldrich, Taipei, Taiwan) were mixed until homogenous in a 7:3 mixture of N,N-dimethyl formamide (DMF; Tedia, Fairfield, OH, USA) and dichloromethane (DCM; Mallinckrodt, St. Louis, MO, USA). Under ambient conditions, the resulting polymer solution was electrospun as a ‘shell solution’ with a ‘core solution’ comprised of polyethylene glycol (Sigma-Aldrich, St. Louis, MO, USA) and polyethylene oxide (Sigma-Aldrich, St. Louis, MO, USA, as described in previous works [ 22 , 25 , 34 ]. Briefly, the high voltage charge supply (You-Shang Co., Fongshan City, Taiwan) generated electrostatic force was set up at 4.5–7 kV also current sustained at 750 µA.…”