Improving cell adhesion on titanium by covalent immobilization of collagen

Initial cell adhesion is a major requirement for the integration of any implant material in the human body. Because it has been established that collagen accelerates receptor-mediated cell adhesion, the aim of the present study was to investigate the influence of titanium modification by covalent attachment of fibrillar collagen on adhesion and proliferation of osteoblastlike cells. Several silane coupling agents and cross-linking molecules have been tested to connect metal and protein, and to stabilize the bound collagen layer against biodegradation. We found that immobilization of collagen was most effective utilizing an amino group-containing silane and a water soluble carbodiimide, the latter performing both covalent attachment and protein cross-linking. In vitro-collagenase digestion revealed higher stability of the covalently bound and cross-linked collagen layer compared to a physically adsorbed and cross-linked collagen layer. Adhesion and proliferation of human osteoblast-like cells (MG-63) was enhanced on titanium biomaterials that have been modified with covalently immobilized and cross-linked fibrillar collagen. References [1] Hallab N. J., Bundy K.J., O ́Connor K. , Moses R. L. , Jacobs J. J.: Evaluation of metallic and polymeric biomaterial surface energy and surface roughness characteristics for directed cell adhesion. Tissue Engineering 7: 55-71, 2001 [2] Rupp F. , Scheideler L. , Olshanska N. , De Wild M. , Wieland M. , Geis-Gerstorfer J.: Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces. J Biomed Mater Res 76A: 323334, 2006 [3] Puleo D. A. , Nanci A. : Understanding and controlling the bone-implant interface. Biomaterials 20: 2311-2321, 1999 [4] Weng W. , Baptista J. L. : Preparation and characterization of hydroxyapatite coatings on Ti6Al4V alloy by a sol-gel method. J Am Ceram Soc 82: 27-32, 1999 [5] Xiao S. J., Textor M. , Spencer N. D. , Sigrist H. : Covalent Attachment of Cell-Adhesive, (Arg-Gly-Asp)-Containing Peptides to Titanium Surfaces. Langmuir 14: 5507-5516, 1998 [6] Rammelt S. , Illert T. , Bierbaum S. , Scharnweber D. , Zwipp H. , Schneiders W. : Coating of titanium implants with collagen, RGD peptide and chondroitin sulfate. Biomaterials 27: 5561-5571, 2006 [7] Park J. C. , Kim H. M. , Ko J. S. : Effects of the extracellular matrix constituents on the attachment of human oral epithelial cells at the titanium surface. Int J Oral Maxillofac Implants 13: 826-836, 1998 ORIGINAL ARBEITEN Rainer Müller: Improving cell adhesion on titanium by covalent immobilization of collagen Figure 5. Stability of covalently and adsorptively bound collagen layers against collagenase digestion. Both collagen layers were cross-linked by carbodiimide reaction (EDC/NHS) whereby covalent attachment was realized on amino group (APS)-modified titanium surfaces and adsorptive binding on surfaces which were only oxidized. Residual collagen was quantified with picrosirius red (n=4). Figure 6. Adhesion (1 day) and proliferation (7 days) of MG-63 osteoblastlike cells on differently modified titanium surfaces. All collagen layers were cross-linked by carbodiimide reaction (EDC/NHS). Cell numbers were determined by the MTS-assay (n=6).