Paper TF-WeA3
Bio Modification of Titanium Surfaces with Grafted Sodium Styrene Sulfonate Thin Films

Wednesday, October 20, 2010, 2:40 pm, Room Pecos

Ti and its alloys are commonly used as biomaterials due to their unique mechanical properties and good corrosion resistance. Still, Ti implants can induce the formation of a fibrous layer that can compromise bonding at the interface with the living tissue. The lack of proper integration of Ti with tissue can lead to implant failure. Since the biological response to implanted biomaterials is initiated at their surfaces, the performance of Ti and Ti alloys can be improved by modifying their surfaces. A promising approach for surface bio-modification is grafting a bioactive polymer onto Ti implant surfaces. For optimal grafting, it is important to fully understand the nature of the bio-modified surfaces since it has a pivotal role in the biomaterial performance. The main thrust of this work is to graft bioactive sodium styrene sulfonate (NaSS) onto Ti surfaces to control and improve their response in biological environment.

Smooth Ti films evaporated onto silicon wafers were used as substrates. XPS showed that the surfaces of these films are covered with a layer of TiO₂. The roughness of these surfaces, as measured by AFM, was 0.7nm. Methacryloxypropyltrimethoxysilane (MPS) was used as a cross linker between the Ti and the NaSS; the substrates were soaked in a solution of MPS in chloroform (5%v/v) for 1 hr at room temperature and then removed from the solution and heated at 140°C for 4 hrs. After attaching the MPS molecules, XPS surface composition and high resolution XPS data suggested that the Ti substrates were covered with a uniform thin film. Additional evidence for the MPS attachment to the Ti surfaces was the appearance of the C_xH_yO_z fragments from the methacrylate group along with the decease of the Ti and TiO_x fragments in the ToF-SIMS data. The NaSS grafting was then done at 90°C in an oxygen free environment for 15hrs using a 0.7M solution of NaSS monomer in dimethyl sulfoxide (DMSO). After NaSS grafting the XPS composition showed an increase of the C/Ti ratio and an appearance of sulfur and sodium. ToF-SIMS successfully detected the sulfonate group, C₈H₇SO₃, and a decrease of the Ti containing fragments. Fourier transform infrared spectroscopy (FTIR) and near edge absorption fine structure (NEXAFS) indicated an ordered array of the grafted NaSS layer on the Ti surfaces and AFM showed a uniform coverage with a roughness of 1.11nm.