Abstract
Due to the good biocompatibility, mechanical properties, corrosion resistance, Titanium and Ti-based alloys are widely applied in the orthopedic implants. However, there are still some problems of the Ti-based alloy implant, such as the elastic modulus of which (cp-Ti, ~105GPa; Ti64,~112GPa) are still far larger than that of real bone (4-40 GPa), which may easily causes stress-shielding effect and subsequently led to the failure of implant. We developed a β-type Ti-28Nb-11Ta-8Zr alloy (TNTZ) with low elastic modulus (49 GPa) as an osseo-compatible material in this study to avoid the problem. Which meets the bone-mimetic condition with improved biocompatibility and corrosion resistance in the environment of simulated body fluid, Hank’s solution. On the other hand, in order to mimic bone extracellular matrix (ECM), the nanotube structure to promote the cell interlocks was carried out by anodic oxidation (AO) with post heat treatment to get crystallization to manufacture crystallized nanotubular oxide layer on the surface. Furthermore, the as-prepared nanostructure oxides serve as a platform utilized to incorporate SrHA inside to devoid of infection during the surgery and assist in surgery and faster healing. Firstly, material characteristics of nanotube TNTZ oxide coating with SrHA were analyzed including surface morphologies by scanning electron microscopy (SEM) and chemical compositions by X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDS). Subsequently, X-ray diffraction (XRD) was used to confirm the crystalline of the nanotube TNTZ oxide structure. Thirdly, cell dehydration and MTT test were conduct to observe the morphology and adhesion of osteoblast on as-prepared NT-TNTZO/SrHA, and the cell proliferation. Finally, in-vitro antibacterial test were applied to observe the antibacterial efficiency. Experimental results indicated that the surface modification through anodic oxidation, diameters of the nanotubes will change with the different apply voltage. Here we applied bias under 50 volt, 60 minutes to grow the nanotube structure as a platform for SrHA (Strontium-hydroxyl apatite) loading to improve the bioability and antibacterial efficiency simultaneously. In the results of SEM image of cell morphology investigation and MTT assay, HA and SrHA-containing provide a more friendly surrounding for osteoblast cells to attach on, and the pseudopod of osteoblast cells can be clearly observed on the SrHA coating treated group. Besides, the enhancements of cell proliferation from crystallinity, SrHA-coating were also found. The final antibacterial tests, qualitative Kirby-Bauer test, inhibited zone observation, reveals that NT-TNTZO/ SrHA effectively inactivate E. coli. Quantitative test of antibacterial efficiency was presented by growth curve of E. coli. The efficiency at least reaches 4 days and 24h respectively in such a strict environment (high volume of bacteria solution). In our study we successfully developed crystal nanotube structure oxide layer loaded with SrHA (NT-TNTZO/SrHA). In the antibacterial test and the in-vitro tests shown that SrHA containing samples enhanced cell viability and antibacterial efficiency simultaneously.