Fig. 3
Scanning electron microscopy (SEM) images of cell attachment on the surface of the silk fibroin (SF) membrane. a SEM image shows the SF membrane surface for day 0, after seeding the initial cell number of 3 × 104. b The cells gradually filled across the fiber texture covering approximately 10–20 % of the SF membrane surface. c At 5 days, the gap between the SF membrane fibers was filled and covered by the cell attachment. d At 7 days, the surface of the SF membrane was nearly filled and covered with cells, to about 90 % confluence, and the fiber texture was nearly totally obscured in the SEM image. 0D cell seeding day, 1D 1 day after cell seeding, 5D 5 days after cell seeding, 7D 7 days after cell seeding