Papers by Author: Guo Yu Lv

Abstract: In the present in vitro study, osteoblasts proliferation, vitality and ultrastructure were investigated when cultured in the presence of silver-hydroxyapatite/titania nanoparticles (nAg_HA/TiO2) compared to HA nanoparticles (nHA) at various concentrations and cell culture without nanoparticles for up to 120 hours. Results confirmed the detrimental influences of both nAg_HA/TiO2 and nHA on osteoblast growth.Cell vitality was slightly higher during the earlier 24h, but after that was inhibited. Both cell proliferation and vitality by addition of nanoparticles were restricted with concentrations of nanoparticles increasing. However, the respiration rates by addition of nanoparticles were showed higher than that of the cell culture without nanoparticles. No remarkable ultrastructure changes were showed in the osteoblasts exposed nanoparticles. The difference in cell proliferation, vitality and ultrastructure between nAg_HA/TiO2 and nHA were insignificant. It was demonstrated that biocompatibility of nAg_HA/TiO2 is almost the same as nHA.

Abstract: Since bacterial accumulation surrounding biomaterials has pathogens known to cause the biomaterials centered infection, it may be important to develop some kind of biomaterial with antibacterial activity as well as biocompatibility. This study focused on evaluating the antibacterial activity of silver-hydroxyapatite/ Titania nanoparticles (Ag-nHA/nTiO2) against oral bacteria with agar dilution method. Bacteria were seeded on agar plate containing antibacterial material with different concentrations after incubation of 48 hours. The antibacterial activity was demonstrated by MICs. The MICs of Ag-nHA/nTiO2 ranged between 1000μg/ ml and 7500μg /ml under anaerobic conditions. And it also exhibited remarkable antibacterial activity to all the aerobe bacteria (MIC≤500μg/ml). On the other hand, the antibacterial activities of Ag-nHA/nTiO2 differentiate to some extent with the bacterial strains. This Ag-nHA/nTiO2 exhibited remarkable antibacterial activity to anaerobic and aerobe bacteria. This antibacterial effect may reduce the potential for bacterial colonisation of oral biomaterials with Ag-nHA/nTiO2.

Abstract: The crystallization behavior of n-HA/PA66 biocomposites at different processing pressure and annealing temperature were investigated by XRD and DSC. The results showed that increasing annealing temperature would weaken the crystalline intensities of pure PA66 and its composites. For n-HA/PA66 composites, the peaks of α1 crystals of PA66 disappeared, only α2 crystals existed, and with the increase of injection pressure and annealing temperature, the crystalline intensity of PA66 decreased. The degree of crystallinity (Xc) of PA66 in composites increased with the increase of injection pressure, however, annealing temperature had no obvious effects on crystalline degree. The mechanical properties had close relationship with the crystallization behavior of the materials.

Abstract: Nano-hydroxyapatite (n-HA) slurry was synthesized at normal pressure, and (Cu2+, Zn2+)-bearing nano-hydroxyapatite (Cu-Zn-HA) was prepared by ion exchange reaction in water medium. The properties of n-HA and Cu-Zn-HA were characterized by AAS, TEM, XRD and FTIR. The results of XRD analysis indicate that Cu2+ and Zn2+ can occupy Ca2+ sites and enter the crystal lattice of hydroxyapatite. Through the antibacterial experiments, it was found that Cu-Zn-HA had better antibacterial ability on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). After heat treatment at 400°C for an hour, the materials still had good antibacterial effect. The accelerated aging method was employed to test antibacterial durability of the material and the results indicated that the durability was good. The results of the security assessment, including skin stimulation test of rabbit, acute toxicity test by stomach filling and the micronucleus test in bone marrow polychromatic erythrocytes of mice, showed that the security of the material was excellent.

Abstract: In this paper, using sodium phosphate and calcium nitrate as reagents, nano-hydroxyapatite (n-HA) was synthesised under 8 conditions. The morphology and crystallinity of these prepared HA were investigated by Transmission Electron Microscope (TEM) and X-ray diffraction pattern (XRD). The Ca/P molar ratio of n-HA was tested by chemical method. In order to find a better way to obtain purer nano-hydroxyapatite, the phases transition and purification of these 8 samples before and after sintering at 1000°C were compared. The results indicated that all these samples showed similar, poorly crystallized apatite structures before sintering. The adding order between calcium and phosphate would affect the crystallinity, structure and Ca/P molar ratio of hydoxyapatite significantly. XRD analysis showed that adding sodium phosphate into calcium nitrate could gain more HA phase after sintering at 1000°C. The pH of reaction system had obvious effects on the structure of hydroxyapatite. Besides the pH of reactants also affected the structure of hydoxyapatite.

Abstract: In this paper a series of silver ions-substituted hydroxyapatites (HA) were prepared. The antibacterial activities of these materials on textiles against bacteria have been investigated. Titania (TiO2) was selectively added into the materials to decrease the silver-ions concentration to get the same active antimicrobial effects. The microstructure, the shape and size, concentration of silver, and the groups of the composite materials were characterized using transmission electron microscopy (TEM), infrared spectroscopy (IR), Atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). The results showed that there was a dose dependent-effect of silver-ions concentration from the disk diffusion test. The higher the silver-ions concentration, the better the antibacterial activity of the composite materials was. Keeping silver-ions concentration constant, the antibacterial activity of the materials for adding Titania was better than that of without Titania. Moreover, the addition of Titania would inhibit the discolouration of the composite materials. The antibacterial activities of the composite materials differentiate to some extent with the bacterial strains.

Abstract: Porous scaffold containing biodegradable Ca-crosslinked alginate(ALG) and nano-hydroxyapatite(n-HA) is synthesized by the freeze-extraction and freeze-gelation methods. The prepared scaffolds were tested by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared absorption spectra (IR), raman spectra, X-ray diffraction (XRD) and burning test. Chemical binding between inorganic n-HA and Ca-crosslinked alginate was investigated. It indicated that n-HA was interacted with Ca-crosslinked alginate. The results of SEM showed that the scaffolds exhibited open-cellular pore structures. The content of n-HA affected the porosity and pore size of the composite. The composite can be a promising scaffold material for tissue engineering.