An amino acid sequence containing the short peptide RGD was ligated with another sequence selected from the crystalline region of Bombyx mori silk fibroin by using the genetic engineering method. The Bombyx mori silk fibroin-RGD fusion protein with the primary structure of [TGRGDSPA(GVP-GV)₂- GG(GAGAGS)₃AS]_n was synthesized with the different molecular weights by regulating the polymerization degree of DNA. The ¹³C isotope labeling of fusion proteins were performed by adding [3-¹³C]Ala in a modified M9 medium during cell cultivation. ¹³C CP/MAS NMR results showed that the GAGAGS region in the fusion proteins tended to take the similar molecular structure to the native silk fibroin protein, i.e., homogeneous silk I structure after treatment or heterogeneous silk II structure after treatment including three structural components. The evaluation of cell biocompatibility to the BALB/3T3 cell line showed that the fusion proteins had higher cell adhesive ability than that of native collagen, even though both have the similar ability on the cell proliferation. These results suggested that the B. mori silk fibroin-RGD fusion proteins may be the candidate for the scaffolds in tissue engineering after suitable processing.

Key words: Bombyx mori silk fibroin, RGD, fusion protein, NMR, cell adhesive ability