2 hydroxy 2 methyl 1 phenyl 1 propanone

The SDS aqueous solution was prepared from sodium dodecyl sulfate (SDS, from Meryer) dissolved in deionized water (from Greagent) at two different concentrations. A 2.5% (w/w) SDS aqueous solution was used as the continuous phase in the experiment of generating hollow-core double emulsions with Fluorinert FC40 oil (purchased from 3 M). A 0.2% (w/w) SDS aqueous solution was used as the continuous phase in the experiments of generating the trimethylolpropane ethoxylate triacrylate (ETPTA) droplets. ETPTA (from Aladdin) was mixed with 0.5% (w/w) of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (from Sigma‒Aldrich). The surface tension between the liquids was measured using the pendent drop method with an optical contact angle meter Dataphysics OCA20.

Negatively charged silica nanoparticles and GelMA were self‐synthesized in the laboratory by the Stöber method according to previous studies.^[41] Gelatin and methacrylic anhydride that utilized for GelMA synthesis, AAm, N,N′‐methylenebis(acrylamide), PEGDA (Mw = 700), 2‐Hydroxy‐2‐methyl‐1‐phenyl‐1‐propanone, trypsin, pancreatin, 5‐bromo‐2‐deoxyuridine and isoproterenol were obtained from Sigma–Aldrich (St. Louis, MO). Cellulose dialysis membranes acquired from Yuanye Biotechnology Corporation (China) were employed for GelMA purification. In the biocompatibility test, 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2, 5‐diphenyl‐2‐H‐tetrazolium bromide was from J&K Scientific Ltd. and dimethyl sulfoxide was derived from Macklin Biochemical Co., Ltd, respectively. SACNTs were achieved from the Beijing Funat Innovation Technology Corporation of China. Dulbecco's Modified Eagle Medium/Nutrient Mixture F‐12, Hanks’ Balanced Salt Solution, fetal bovine serum, cellular dyes including Alexa Fluor 488 Phalloidin, and 4′,6‐diamidino‐2‐phenylindole were all acquired from Life Technologies (USA). Worthington provided collagenase type 2, while Gibco (USA) supplied penicillin‐streptomycin and phosphate‐buffered saline solution.