Functionalization of titanium disks to improve osseointegration

Abstract

Titanium implants are nowadays often used in orthopedics and dentistry to repair or replace bone injuries or defects caused by aging, accident or diseases. Even if titanium is biocompatible, a low osseointegration between the implant and the surrounding tissue may result in graft rejection and a series of unwanted reactions. To overcome these issues, two main strategies have been investigated: a physicochemical modification of the implant surface (e.g. roughness, energy or chemistry of the surface) or a functionalization of the surface with cell adhesive molecules. This research project will mainly focus on the second approach which consists on the biofunctionalization of the surface. There are many types of cell adhesive molecules that can be used for such purpose. One of the most common family of cell adhesive molecules used are the proteins found in the extra cellular matrix (ECM).The cell bonding activity of these proteins is usually contained within a few amino acids. This is the case of the sequence Arg-Gly-Asp (RGD) found in many proteins of the ECM. Thus, the use of these short peptide sequences has been explored to biofunctionalize materials and to improve cell adhesion. To create a covalent and stable binding between the peptides (organic molecules) and the titanium surface (inorganic surface), the use of linker molecules is required. This can be achieved by using organosilanes. The aim of this project is to improve the adhesion of the osteoblasts onto the titanium graft. In order to do so, different activation methods of the titanium surface will be explored followed by a silanization step that ensure the attachment of the peptides to the surface. Then, RGD peptides will be immobilized to improve the binding of the cells on the surface. The central theme of this research will be to compare two methods that increase and accelerate the adhesion of the cells in order to decrease the risk of complications. The first method is a simple physisorption of the peptide onto the implant surface and the second method is a creation of a strong covalent bond between the surface of the implant (made of titanium) and the peptides. The effect of the distinct activation treatments on the physicochemical properties of the surfaces will be investigated by means of contact angle measurements, interferometry, scanning electron microscopy and X-ray photoelectron spectroscopy. The biological properties of the functionalized materials will be explored by means of cell adhesion assays with osteosarcoma cells.