Modification of the adhesive properties of collagen by covalent grafting with RGD peptides

Collagen, either alone or in combination with other materials, is an import ant natural biomaterial that is used in a variety of tissue-engineering app lications. Cell adhesion and migration of cells within collagen-based bioma terials may be controlled by modifying the adhesive properties of collagen. Furthermore, spatially controlling the adhesiveness of the collagen may al low controlled localization or redistribution of cells. A method is present ed for covalently coupling peptides that contain the well-characterized arg inine-glycine-aspartic acid adhesion sequence directly to type I collagen m onomers prior to fibrillogenesis. A heterobifunctional coupling agent was u sed to create stable amide and disulfide bonds with the lysine residues of the collagen monomers and the cysteine termini of the peptide molecules, re spectively. The degree of conjugation could be controlled by changing the r eaction conditions (ratios of reactants added and the length of incubation) . The microstructure and gelation times of gels composed of covalently modi fied collagen were similar to those of unmodified gels. Cell adhesion on ad sorbed monolayers of modified collagen was quantified using a well-establis hed clonal cell line (K1735 murine melanoma). Cell adhesion was found to in crease with both increasing degree of conjugation and increasing ratio of m odified to unmodified collagen.