After a week of incubation, the cells on the scaffolds were washed twice with PBS and then fixed with 2.5% glutaraldehyde at 4 °C for 4 h. Part of the cell-seeded scaffolds were stained with TRITC-Phalloidin (Solarbio, CA1610, Beijing, China) and DAPI (Solarbio, C0060, Beijing, China) after being permeabilized with 0.5% Triton X-100 solution (Beyotime, P0096, China). And the fluorescent images were captured by a confocal microscope (Eclipse, NIKON, Japan). Meanwhile, the remaining scaffolds were dehydrated through a gradient of ethanol (50, 60, 70, 80, 90, and 100%), followed by drying in a vacuum. The specimens were gold-coated and observed with scanning electron microscopy (SEM, VEGA 3 LMU, Tescan, CZ).