Chondrocyte-material adhesion plays an essential role in cartilage synthesis, and it is important to evaluate the adhesion quantitatively. In this study, we measured the adhesive force between chondrocytes and two types of Arg-Gly-Asp-Ser (RGDS)-containing silk fibroin substrates: RGDS-transgenic fibroin (RTF) in which a tandem repeat of RGDS sequence was genetically interfused in the fibroin light chain; and RGDS-mixed fibroin (RMF) which is a mixture of wild-type fibroin (WTF) and commercial RGDS peptides. The results showed that chondrocytes grown on the RTF substrate exhibited higher force than those grown on the WTF substrate, however, there were no significant differences between the WTF and RMF groups. Considering that the integrin β1 mRNA expression level showed the same tendency as the adhesive force in comparison among the three groups, integrin-mediated biological interactions can be predominant in changes in chondrocyte adhesive force. This theory is also supported by the results that the introduction of RGDS had no effects on the surface properties of the fibroin substrates and that chondrocyte attachment to the RGDS-containing fibroin substrates was inhibited by the addition of RGDS peptides to the medium.
