| Porous anodic alumina(PAA) is a kind of long-range ordered self-assembly materials with nano-pore arrays. It has been widely used in various fields such as nanomaterials preparation, substance separation and so on. At present, the research is mainly based on small-diameter PAA, whereas the ordered large-diameter PAA is currently a research focus and a difficult problem. In addition, PAA has good chemical stability, biocompability and biomimetic structure, and has shown great potential in the practical application of medical metal surface coating modification. However, PAA is inherently bioinert, thus could not form efficient osseointegration with surrounding bone tissue. Therefore, it is significantly important to improve the surface properties of PAA. Due to the large area of paralled and hexagonally arranged nano-pores of PAA, it can also be used as an excellent carrier of bioactive substances, thereby endowing it with particular biological functions. In recent years, numerous studies have shown that calcium-silicon (CaO-SiO2) bioactive materials have excellent bioactivity and biodegradability, where the materials can rapidly induce bonelike apatite deposition and promote the bone-related cells proliferation and differentiation. The silver ions have broad-spectrum and efficient antibacterial effect. Therefore, through designing of silicon-calcium-silver (Ca0-SiO2-Ag2O) ternary system of bioactive glass and loading them into the PAA pores, thus making it possible to combine the material properties of treatment, repair and infection prevention together, which has significant theoretical and medicinal value.At first, ordered large-diameter PAA was prepared by an improved two-step anodization approach. Then, field emission scanning electron microscopy(FESEM), energy dispersive X-ray spectroscopy(EDS) and X-ray diffraction(XRD) were used to characterize the morphology, structure and composition of PAA. A systematic study was carried out to investigate the effect of anodization voltages, voltage matching on the pore diameter, interpore distance and regularity of PAA. In order to endow PAA surface with bonelike apatite formation ability, the phosphorylation treatment of PAA was performed by impregnating them in phosphoric acid at low temperature and a subsequent heat treatment. The apatite-forming ability of phosphorylated PAA was evaluated by soaking them in simulated body fluid(SBF). PAA, phosphorylated PAA and the in vitro apatite formation on phosphorylated PAA specimens were characterized by means of FESEM, EDS and fourier transform infrared spectroscopy(FTIR). The CaO-SiO2and CaO-SiO2-Ag2O sol were prepared using a sol-gel method, then filled into the pores of200nm PAA by vacuum impregnation method, CaO-SiO2/PAA, CaO-SiO2-Ag2O/PAA composite biomaterials were eventually prepared by these preparation techniques. A preliminary study of the in vitro bioactivity and ion release behavior of CaO-SiO2-Ag2O/PAA were carried out by soaking them in SBF. The antibacterial activities of PAA, CaO-SiO2/PAA, CaO-SiO2-Ag2O/PAA and the morphology changes of bacteria on the surface of these materials were also investigated. The conclusions are as follows:The PAA prepared by the improved two-step anodization approach are hexagonally close-packed, orderly arranged. The EDS measurement result shows that the specimen mainly contains Al and O element. The XRD result indicates that the specimen is amorphous. A serial highly ordered large-diameter PAA were prepared by the improved two-step anodization approach under the voltages of100-140V. The pore diameters are in the range of200-300nm, and the interpore distance is in the range of260-350nm. Furthermore, there is a linear relationship between interpore distance and anodization voltages, and the proportionality constant is2.29nm/V. When the disparity of the two-step anodization voltages was too large(first anodization voltage:40V; second anodization voltage:100V), the nanopores were not uniform and disorderly arranged. Then the well-arranged and hexagonally close-packed PAA can be formed when the two-step anodization voltages were completely matched(first anodization voltage:100V; second anodization voltage:100V). In the experiment of phosphorylation treatment, the EDS analysis indicated that the phosphate species were introduced onto the PAA surface, while FTIR results confirmed that through the phosphorylation treatment, the negatively charged-PO4H2groups could be introduced onto PAA surface. The SBF soaking test showed that the phosphorylated PAA has excellent ability to induce bonelike apatite formation. The FESEM observations of CaO-SiO2/PAA and CaO-SiO2-Ag2O/PAA showed that the bioactive glass almost filled the entire PAA channels without too much coving layer on the surface. The SBF soaking test indicated that CaO-SiO2-Ag2O/PAA possess excellent ability to induce the formation of bone-like apatite and favourable ion release properties. The results of antibacterial activities showed that, after24h of incubation, the inhibition rates of CaO-SiO2-Ag2O/PAA to E. coli and S. aureus were90%and92%, respectively. While the inhibition rates of CaO-Si02/PAA to E. coli and S. aureus were35%and41%, respectively. The results of morphology changes of bacteria on the materials showed that, the E. coli and S. aureus on PAA surface displayed smooth and intact., the morphology changes on CaO-SiO2/PAA was not obvious, while obvious death cells and lysed cells were observed on CaO-SiO2-Ag2O/PAA. |
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