Utilização do compósito P(VDF- TrFE)/Batio3 como revestimento de implantes da liga Ti-30Ta para aplicações biomédicas

Abstract

Titanium and its alloys are widely used as biomaterial for fixation and replacement of bone tissue due to their mechanical properties and their biocompatibility, which can promote to the patient a fast recovery. However, commercially pure titanium is considered as bioinert material and his Young’s modulus (110GPa) is higher when compared to the bone tissue modulus, which corresponds to the range of 10-30 GPa. For this reason, it is sought to add elements to the titanium while maintaining its biocompatible characteristics. Thus, the Ti-30Ta alloy was chosen for this study, which has Young’s modulus more compatible with the bone when related to titanium. Nevertheless, in order to promote osseointegrative properties to the implant, it is possible to cover its surface using biocompatible and biofunctional films. Therefore, biomaterials with piezoelectric properties, such as P(VDF-TrFE) copolymer and BaTiO3 ceramics, were adopted with purpose of covering Ti-30Ta substrates in order to promote the electrostimulation of bone cells and favor the osteogenesis process. For this research, the material was synthesized and deposited on the Ti-30Ta substrate using the spray technique at low temperature. The characterization of the composite was carried out using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), Surface Energy, Wettability and Roughness. For the evaluation of the adhesion of the film in the substrate was used the technique of Scratch Test and the mechanical behavior of the material was evaluated by the Microhardness Vickers and Modulus of Elasticity. The electrical resistivity was obtained through the Impedance Test (AC). In order to evaluate the microbiological activity of the material, were used Staphylococcus aureus and Staphylococcus epidermidis bacteria. The behavior of blood cells when in contact with the material was evaluated by the hemocompatibility test. The results obtained by means of the techniques mentioned above indicate that the coating film demonstrate surface characteristics as wettability – with hydrophilic surface corresponding to a contact angle of 80°, average roughness of 0,24 µm and surface energy corresponding of 40,7 mN/m2 , which are considered adequate to promote cell-implant interaction. In addition, it has also been found that the coating material has thermal stability up to 450°C and presents the piezoelectric phase up to approximately 140°C. Regarding the adhesion of the film on substrate, was observed that through the sanding technique performed on surface, the film behaved in a superior way to the other samples, being the critical load to cause failure in the covering corresponding to 8MPa. Biological assays have shown that the material presents hemocompatible characteristics when in contact with blood cells. The microbiological assay showed that for the Staphylococcus aureusthe bacterial growth in the coated did not present significant differences when compared with de uncoated alloy. In the case of Staphylococcus epidermides, there was a considerable growth in coated alloy in relation with the uncoated alloy. These results can indicate that the film surface may have provided bacterial growth. However, based on the results presented, it can be concluded that the Ti-30Ta alloy coated with P(VDF-TrFE)/BaTiO3 is promising for biomedical applications, especially when used as dental and facial implants.