Gelatin type a from

The BETA scaffold was manufactured, as previously described [21 (link)]. Briefly, the copolymer emulsion of poly(ε-caprolactone) (PCL: Sigma-Aldrich, Saint Louis, MO, USA, Mn 80,000), and gelatin (Type A from porcine skin, Sigma) dissolved in TFE ((2,2,2-trifluoroethanol; Roth) were spin-coated (2000 rpm) and were dried under vacuum (300 mbar). The optimum mixing ratio of 9.35% PCL and 6.34% gelatin [w/v solvent] was used for the co-polymer of PCL/gelatin as previously described [22 (link)]. Membranes were sterilized before cell culture experiments with PBS, ethanol 80%, and UV exposure. Scanning electron microscopy (SEM, Zeiss Crossbeam 340, Carl Zeiss AG, Oberkochen, Germany) was used to study the morphology of the BETA scaffolds. The cells were fixed in 2% v/v glutaraldehyde (GA; Sigma-Aldrich) and then dehydrated in gradient acetone solutions (Sigma-Aldrich) followed by hexamethyldisilazane (HDMS, Sigma-Aldrich) for 15 min. The samples were subsequently sputter-coated with platinum and analyzed at an operating voltage of 2 kV.

Gelatin (type A, from porcine skin) and chitosan (low molecular weight) was purchased from Sigma-Aldrich (Shanghai, China). Methacrylic anhydride was purchased from Aladdin (Shanghai, China). 3,4-Dihydroxyhydrocinnamic acid, N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), ethanol (AR, 99.7%), DL-dithiothreitol (DTT) and zinc chloride (ZnCl₂) were purchased from Macklin (Shanghai, China). CCK-8 proliferation assay kit was purchased from Beyotime (Shanghai, China). Dulbecco’s modified Eagle’s medium/Ham’s F-12 medium (DMEM/F-12), induction media (osteogenic, chondrogenic and adipogenic) and fetal bovine serum (FBS) were ordered from Invitrogen. Cell culture plate was ordered from Corning.