Yu Bao Li

Antibacterial Activity of Silver-Hydroxyapatite/Titania Nanocomposite Coating on Titanium against Oral Bacteria

This study was focused on evaluating the bactericidal and anti-adhesive efficacy of silver-hydroxyapatite/ titania nanocomposites (nAg-HA/TiO2) coating on titanium against oral bacteria. Porphyromonas gingivalis, Prevotella intermedia and Fusohacterium nucleatum and Streptococcus mutans were used. Antibacterial activity of nAg-HA/TiO2 coating was investigated quantitatively using film applicator coating method and titanium plates incubated with bacteria were prepared for SEM to observe the adherence of oral bacteria. The viability of each type of bacteria on the antibacterial film was suppressed to about 10% after anaerobic incubation for 3 hours. Image of SEM demonstrated that bacteria on sandblasting surfaces were relatively confluent whilst on coated surfaces fewer bacteria were observed. Adherence of bacteria on nAg-HA / TiO2-coated surfaces compared with uncoated surfaces was remarkably decreased.

Novel Method to Fabricate Porous n-HA/PVA Hydrogel Scaffolds

Porous n-HA/PVA hydrogel composite was prepared through in-situ hydrothermal treatment under normal pressure and emulsion foam freeze-drying method, which was used to fabricate porous hydrogel. The pores exhibited interconnection-pore structure owing to the injection of air bubbles and the removal of emulsifier (OP). The porous hydrogels were investigated by using IR, XRD, TEM and SEM. The results indicated that n-HA in the composite could disperse uniformly, and there were chemical bonding with PVA. In addition, nano-hydroxyapatite existed in the composite in the shape of short-rod. The pores were interconnection with narrowly pore size and highly porosity. And the pore size and size distribution were influenced by the weight of OP. The emulsion foam freeze-drying method can be used to prepare porous hydrogel scaffold for tissue engineering, or to contain proteins scaffold, because of operating at a low temperature. The method displayed a vast potential of applied foreground.

Study on crystallisation of nano-hydroxyapatite/polyvinyl alcohol composite hydrogel

Abstract Composite hydrogels of nano-hydroxyapatite (n-HA)/polyvinyl alcohol (PVA) were prepared by solution and freeze thawing methods in this paper. The effect of different n-HA content on PVA melting point, crystallinity and mechanical property was studied. Differential scanning calorimetry measurement exhibited a decrease in the crystallisation temperature and crystallinity of PVA with the addition of n-HA. The reason should be that hydrogen bonds in PVA macromolecule are destroyed when PVA form bonding with n-HA, thus suppressing the crystallisation of PVA polymer chains. Mechanical property test of the composite hydrogels reveals that the tensile strength is correlated with PVA crystallisation; the higher the crystallisation of PVA, the greater the tensile strength. The n-HA also lowers the water absorption ratio of PVA hydrogel.

Study on the Biomimetic Properties of Bone Substitute Material: Nanohydroxyapatite/Polyamide 66 Composite

To compare with the human cortical bone, the biomimetic properties of nano-hydroxyapatite/polyamide 66 composite (n-HA/PA66) were preliminarily studied qualitatively and quantitatively with TEM, XRD in crystal morphology, phase composition and crystal structure. A series of structure parameters such as cell lattice parameters (a and c), mean crystallite size and micro-strain were calculated to characterize quantitatively the microstructure of n-HA/PA66 and human cortical bone at the atomic level. The results show that n-HA/PA66 is a good biomimetic biomaterial. But there still are some differences between n-HA/PA66 and human cortical bone. Compared to human cortical bone, the crystal microstructure of n-HA/PA66 is denser, the crystal lattice of n-HA is more perfect and the distortion of crystal lattice decreases.

Antibacterial Effect and Security Evaluation on Nano-Hydroxyapatite Bearing Cu2+ and Zn2+

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.

Preparation and in vitro evaluation of polyurethane composite scaffolds based on glycerol esterified castor oil and hydroxyapatite

Abstract Sponge-like polyurethane (PU) and composite have recently attracted attention in biomedical field as scaffolds for bone repair or tissue engineering research. In this study, castor oil was transesterified with glycerol to increase its functional hydroxyl groups and improve the mechanical properties of the resulting composite scaffolds. The glyceride of castor oil (GCO) was used to copolymerise with isophorone diisocyanate to generate PU, meanwhile blending with hydroxyapatite (HA) powder to prepare porous HA/PU composite scaffolds. The HA/glyceride based PU (GCPU) scaffolds were compared with pristine castor oil (PCO) based PU scaffolds (PCPU) by investigating the physicochemical properties and cytocompatibility using Fourier transform infrared, X-ray diffraction, SEM, mechanical testing and methylthiazolyldiphenyl-tetrazolium bromide assay. The results showed that the number of hydroxyl groups of GCO was nearly twice as high as that of PCO, which enhanced efficiently the crosslinking density of PU matrix. The compressive strength of HA/GCPU scaffold with 40 wt-%HA was ∼4·6 MPa, much higher than that (0·058 MPa) of HA/PCPU scaffolds. The in vitro biological results demonstrated that both GCPU and HA/GCPU scaffolds exhibited desirable cytocompatibility. The novel synthetic route is highly effective for the preparation of HA/GCPU porous scaffolds, which have good prospect in the repair of bone defects or for bone tissue engineering.

Antibacterial Activity of Silver-Hydroxyapatite/Titania Nanoparticles on Oral Bacteria

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.

Synthesis and Characterization of n-HA/PVA/Gel Composite

A unique composite consisted of nano-hydroxyapatite (n-HA), poly (vinyl alcohol) (PVA) and gelatin (Gel), was prepared and characterized by Fourier transform infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and burning test. The homogenicity of the composite was evaluated, and the presence of interior chemical bond was confirmed and discussed. Mechanical strength and water absorption of the prepared composite were investigated, respectively. The results show that n-HA/PVA/Gel composite has good homogeneity, similar mechanical properties to natural cartilage and excellent in vivo biocompatibility.

Comparison of Hydroxyapatite Synthesized under Different Conditions

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.

In vitro evaluation of antibacterial activity and cytotoxicity of novel nanocomposite material for bone filling

Abstract In this study, silver ion substituted nanohydroxyapatite, titania nanoparticles and polyamide 66 composite bone filling materials were prepared, which were expected to be a suitable bone repair material with good antibacterial activity, biocompatibility and osteoconductivity, for use in osteomyelitis surgery. The antibacterial activity and release of Ag ions in vitro were evaluated. Two types of bacteria strains, Staphylococcus aureus and Escherichia coli were used in this test. The results showed that the composite materials exhibited significant antibacterial effects on the two bacteria. Time course release testing of Ag ions from the composite materials on immersion in simulated body fluid showed pronounced Ag release in the first several days after immersion, and then the release speed slowed down after 14 days. International standard ISO 10993‐12:2007 was adopted for cytotoxicity evaluation using fibroblast cell line L929, and it was found that the cytotoxicities for the composite materials ranked are all within 1, which showed no cytotoxicity for the composite materials.