Papers by Keyword: Nanohydroxyapatite (HA)

Abstract: Acicular nano-hydroxyapatite (n-HA) was used to make a new biomaterial composite with polycarbonate by a novel technique. The physical and chemical characteristics of the composites were tested. It was found that the synthesized n-HA crystals were similar to bone apatite in size, phase composition and crystal structure. The TEM results indicated the biomimetic n-HA crystals were uniformly distributed in the polymer matrix. Chemical inter-action between inorganic n-HA and polycarbonate was investigated and discussed. These results indicate that the composite fulfills the basic requirement of bone substitute material, and has the potential for clinical applications.

Abstract: Proper thermal treatments allowed to modify the number of surface Ca2+ able to coordinate water molecules on the surface of hydroxyapatite (HA) nanoparticles surrounded by an amorphous layer. Despite the consequent significant difference in the first hydration level between untreated and treated HA, the amount of adsorbed BSA, used as a model protein, remained essentially unchanged and the native structure of adsorbed protein was retained (as indicated by mid-IR ATR). Near-IR spectroscopy evidenced that adsorbed proteins should be in direct contact with surface Ca2+ through a displacement of H2O molecules by charged acidic residues. In agreement with a previous study that evidenced the heterogeneity of surface Ca2+ ions in terms of Lewis acidity, it was then proposed that the adsorption of BSA on such nano-HA should be ruled by some feature of the local structure of surface Ca2+ sites, prevailing on the total number of cationic sites exposed and the related features of the first hydration layer.

Abstract: L9 (34) orthogonal array design was employed to optimize experimental conditions for the preparation of the composite using in situ synthesis method and to analyze the relationships between experimental parameters and mechanical property of the composites. Bending strength of the composite was considered as a target property of the composites. Hydroxyapatite content in the composite, synthesis temperature and pH were chosen as main parameters. As a result of this study, bending strength of the composite appeared in peak with the increase of the hydroxyapatite content of the composites and synthesis pH, while with the increase of temperature, bending strength decreased. Optimum experimental conditions for the synthesis of the composites with higher bending strength were determined. The bending strength of the composites was 90 MPa at the optimal synthesis conditions.

Abstract: Scaffold in bone tissue engineering must have a three-dimensional (3-D) interconnected porous structure acting as a template for bone tissue regeneration, and material fabricating the scaffold must be biocompatible and can provide structural support during bone growth and remodeling at the same time. In this paper, a method of phase separation and particle leaching combined (PS/PL) was used to prepare porous scaffold of nano-hydroxyapatite and polyamide6 (n-HA/PA6) composite. The results show that the scaffold prepared by PS/PL has not only interconnected macropores of 100~300 μm, but also micropores on the walls of macropores, and PS/PL scaffold is more interconnective in compare with phase separation (PS) scaffold. When the porosity of the scaffold is about 79%, its compressive strongth is about 3.27 MPa, that is similar to the human cancellous bone(2~10MPa). Ethanol has some effect on hydrogen bonds, but fabricating method will not change the chemical component of the composite. The porous scaffold is prospect for bone tissue engineering.

Abstract: A novel nano-hydroxyapatite/chitosan (n-HA/CS) composite scaffold with high porosity was developed by a new method of emulsion-foaming/freeze-drying process and was characterized by means of infrared spectroscopy (IR), scanning electronic microscopy (SEM) and universal material testing machine. In addition, the porosity and density of the scaffold were also calculated. IR result shows that the characteristic absorption peaks belonging to both CS and HA are present in their composite, and the slight band-shifts and peak-decrease suggest that some interactions have taken place between the two phases of CS and n-HA in the composite. SEM photo displays that, with the dosage increase of Tween-80, the prepared scaffold shows highly porous and interconnected structure, in which macropores and micropores coexist. The calculated data demonstrate that the porosity of the scaffold is proportional to the content of the emulsifier, while the compressive strength is inversely. When 15wt% emulsifier used, the porosity of the scaffold can be up to 90% and the density is 0.453g/cm3, while the corresponding compressive strength is about 2.4MPa. The newly developed n-HA/CS composite scaffolds may serve as a good 3-D substrate for cell attachment and migration in bone tissue engineering.

Abstract: Nano-hydroxyapatite/polyamide66/chitosan composite (n-HA/PA66/CS) was prepared by a co-precipitation method and porous scaffolds from n-HA/PA66/CS composite were prepared by means of porogen–leaching method and were characterized by SEM, IR, XRD and universal mechanical testing machine. IR and XRD analyses showed that some chemical bonds existed between n-HA and polymers. Furthermore, macroporous structure of the scaffolds and mechanical strength were tested with a changed ratio of porogens (PVP/NaCl). When the ratio of PVP and NaCl is1: 6, the scaffold processed highly porosity and the pores were interconnected. The compressive strength of the scaffold, can meet the requirement of tissue regeneration.

Abstract: The objective of this study was to investigate the inhibitory effect of the synthetic nanohydroxyapatite (HA) on dental caries. The nano-HA was synthesized by using the depositing reaction of Ca (H2PO4)2. The artificial dental caries was made by using sour solution and inoculating Streptococcus mutans (S.mutans) to the Sprague-Dawley (SD) rat’s mouth respectively. After mineralization of solution of nano-HA for 10 days, the hardness of enamel was measured. The inhibitory effect of the synthetic nano-HA on dental caries was detected by gargling way to rinse the rat tooth with the solution of nano-HA in the animal test. Transmission electron microscopy (TEM) revealed that the dried HA particles were needle-like with ф5-20nm×60nm and the sintered HA particles were spherical with less than 100nm. The remineralized test indicated that the solution of nano-HA with different shapes enhanced the hardness of artificial caries and improved the remineralization of artificial caries. The animal test showed that the dried nano-HA had the inhibitory effect on dental caries. The good absorptive effect of the nano-HA on both the saliva protein and the glucans leads to the development of interventions that could reduce or modify bacterial colonization of tooth surfaces.

Abstract: Poly 3-hydroxybutyrate (PHB) as a kind of polysaccharides has been proved promising for tissue engineering because of its biocompatibility and biodegradability. But its poor mechanical properties and hydrophilicity limit its application. In order to explore a new useful porch to improve the performance of PHB-based GTR membrane, membrane composed of nano-HA / PHB composite was manufactured through the air/jet electrospinning process which can potentially generate nanometer scale diameter fibers and enlarge surface area of materials while maintaining high porosity. Successively, the biomineralization behavior of the membrane in supersaturated calcification solution (SCS) was studied. The Results of this investigation show that the successfully manufactured porous nano-HA/PHB membrane has high activity in SCS and its ability of inducing the formation of mineral crystal in vitro than that of the unfilled PHB membrane. It can be concluded that the addition of nano-HA and the novel technology could improve the performance of the PHB-based GTR membrane.

Abstract: 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.

Abstract: Hydroxyapatite/collagen composites were prepared in-situ synthesis. The composites were finally achieved by dehydration including air-drying and freeze-drying methods. FTIR, XPS and DSC were employed to investigate the composites dehydrated by two methods. The air-dried composites had better mechanical properties than those of the composites dried by freeze drying. Air-drying of the composite induced more bond formation and crosslink between collagen fibers and HA crystals compared with freeze-drying of the composite, as indicated by the shifting of amide A and I bands to the lower wavenumber and by the changes in the binding energy of O1s, Ca2p, and P2p, leading to the increase of the peak temperature of the composites. Collagen crosslink and bond formation in the air-dried composites were key factors to increase the bending strength of the composites. The results of this study confirm that in situ synthesis and air-dry method are effective ways to obtain nanoHA/COL composites with high mechanical properties.