TMAO hydrogel disks with 1 wt % cross-linker were soaked in 70% ethanol for 2 hours for sterilization and soaked in sterilized PBS until equilibrium. NIH 3T3 fibroblasts were respectively seeded onto TMAO hydrogel disks at a concentration of 105 cells/ml into 24-well plates. The same procedure was conducted on TCPS hydrogel disks with the same surface area as the control. The cells were cultured at 37°C, 5% CO2, and 100% humidity for 72 hours and then were observed and photographed on a Nikon Eclipse TE2000-U microscope at ×100 magnification.