Fibronectin solution

A photo-crosslinker was used to minimize sample contraction [54 (link),55 ]. According to various papers using Sulfo-SANPAH, it has been proven that there is no effect on cells in the case of long-term experiments [54 (link),55 ,56 (link)]. A high-power UV curing device (JHCI-051BS-V2; Jueun UV Teq Anyang, Korea) was used after filling the FSOC cell chamber with 10 mM sulfo-SANPAH (Proteo Chem, Hurricane, UT, USA; Figure 9). The device is used to expose for 45 min under a high-power UV (wavelength 365 nm) of 400 W at a distance of about 15 cm from the PDMS surface. During this process, a nitrophenyl azide reaction occurs and the sulfo-SANPAH molecules become perpendicular and bind to the PDMS surface. Next, the cell chamber was then cleaned with PBS, filled with a fibronectin solution (0.66 mg/mL Corning Inc., New York, NY, USA), reacted to the cell chamber for 3 h at 4 °C, then cultured in the cell. During this process, fibronectin binds to the amine group at the end of the sulfo-SANPAH attached to the PDMS surface. The bound fibronectin then binds strongly to the 3D culture support, collagen, and prevents contraction during culture.

FN-coated polyacrylamide gel substrates with stiffness 6, 10, and 16 kPa were respectively established as the method described previously except for the coated matrix protein (13 (link)). A gel substrate with a diameter of 6 cm was coated with 320 μl fibronectin solution (0.17 mg/ml, Corning, NY, United States).