Papers by Author: Na Ru Zhao

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Authors: Gang Wu, Ying Jun Wang, Hua Ding Lu, Xiao Feng Chen, Jian Dong Ye, Cheng Yun Ning, Na Ru Zhao
Abstract: In this article, a multilayer tissue engineering scaffold has been fabricated. The uppermost layer is consisted by the collagen and the downmost layer is consisted by the collagen/hydroxyapatide. Between the two layers, there have several continues changed collagen/HA layers at different ratio. These gradient scaffolds have been made by the freeze dried method. The morphology of the multiphase scaffold has been observed by the SEM. The chondrocytes from New Zealand rabbit knee joint were separated, harvested and cultured on the top layer of the scaffold. The histological and the immunohistochemical testing show that the chondrocytes keep its normal type in the 2 culture weeks.
Authors: Xiao Feng Chen, Ying Jun Wang, Chun Rong Yang, Na Ru Zhao
Abstract: The bone tissue engineering scaffold was developed by compounded the type I collagen with the porous scaffold of the sol-gel derived bioactive glass (BG) in the system CaO-P2O5-SiO2. The resultant porous scaffold was treated in supersaturated calcification solution (SCS) to form the surface layer of hydroxyl-carbonate-apatite (HCA) since the type I collagen possessed good biocompatibility and bio-absorbability, and also, the ability of inducting calcium phosphates to precipitated inside and outside the collagen fibers where the collagen fibers acted as bio-macromolecules template for formation of bone-like inorganic minerals in nature bone such as: octo-calcium phosphate (OCP), tri-calcium phosphate (TCP) and hydroxyl-carbonate-apatite (HCA). On the other hand, the sol-gel derived bioactive glass also played an important role in formation of the above bio-minerals owing to its serial chemical reactions with the body fluid. The in vitro study in supersaturated calcification solution SCS indicated that the surface of the porous scaffold was able to induce formation of bone-like HCA crystals on the pore walls of the scaffold which possessed satisfactory cells biocompatibility.
Authors: Xiao Feng Chen, Jing Hu, Na Ru Zhao, Yong Chun Meng, Yu Li Li
Abstract: The bioactive glass is used widely as bone-repairing material due to its excellent bioactivity, biocompatibility and the function for bone restoration, which depended, to a great extent, on the composition, microstructure of the glass and the process conditions. In this study, effect of process conditions (the melting temperature and time) on compositions, microstructure and the properties of bioactive glass was analyzed using EDS, Density measurement, XRD and FTIR techniques. The results indicated that compositions and microstructure changed because of the selective evaporation of constituent and the change in homogeneity of components.The bioactivities of the glasses prepared under different process conditions were characterized by immersing the glass particles in simulated body fluid (SBF) combined with FTIR technique. The results indicated that hydroxyl-carbonate-apatite (HCA) layer formed on the surface of the samples after 24 hours soaking in SBF. A quantitative method was used to compare the bioactivity of samples. It indicated the different preparation processes had influence on the bio-mineralization properties. Then the optimal preparation condition (1450°C, 30min) was obtained.
Authors: Na Ru Zhao, Ying Jun Wang, Xiao Feng Chen, Cheng Yun Ning
Abstract: In this study, the bioactive composites based on β-tricalcium phosphate (β-TCP), bioglass (BG) and poly lactic acid (PLA) were prepared. The microstructure, degradability and reaction products of the scaffold soaked in a simulated body fluid (SBF) at 36.5°C for different days were characterized through scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) and induced coupled plasma spectroscopy (ICP). The weight loss and strength decrease with the time were tested. The results showed that at the same porosity, the degradability of the scaffold samples decreased as followed: β-TCP/BG/PLA>β-TCP/BG>β-TCP.The materials had highly bioactive response ability to the Simulate Body Fluid (SBF) and promptly induced a bone like HA layer on the surface of the scaffolds when immersed in the SBF.
Authors: Xiao Feng Chen, Ying Jun Wang, Na Ru Zhao, Chun Rong Yang
Abstract: The new type of bone tissue engineering scaffold composed of the sol-gel derived bioactive glass particles, type I collagen, hyaluronic acid and phosphatidylserine were prepared through cross-linking and freeze-drying techniques. SEM observation indicated that the scaffold possessed a 3-D interconnected porous structure and a high porosity. The properties of bio-mineralization and cells biocompatibility were investigated using SBF immersion and cells culture methods combined with SEM, XRD and FTIR techniques. The study revealed that this biomimetic scaffold possessed satisfactory functions of cells attachment, bio-mineralization, and cells biocompatibility. The porous structure and the surface of the scaffold which was covered by a bone-like HA crystal layer due to bio-mineralization were profitable for cells attachment and spread.
Authors: Hua De Zheng, Ying Jun Wang, Chun Rong Yang, Xiao Feng Chen, Na Ru Zhao
Abstract: The spherical nano-sized bioactive particles in the system of CaO-P2O5-SiO2 were bio-mimetically synthesized using micro-emulsion method. The microstructures and properties of the bio- mimetic nano-materials were characterized using XRD, FTIR, SEM/EDAX and TEM techniques. It was indicated that the nano-particles possessed glassy structural characteristics. The porous composite for bone tissue reconstruction was prepared by compounding poly (hydroxybutyrate-2-co-2-hydroxyvalerate) (PHBV) and the nano-particles of bio-mimetic bioactive glasses (BMBG). Bone-like hydroxyl- carbonate-apatite (HCA) could formed on the surface of porous composite by immersing the composite in simulated body fluid (SBF) at 37°C for 8 hours. With increase of immersion time, the morphology of HCA changed from spherical into flake-like crystals. The study on cells attachment of the porous PHBV/BMBG composite proved that the material possessed satisfactory bioactivity, bio-mineralization function and cells biocompatibility.
Authors: Tao Jin, L.R. Liu, Na Ru Zhao, Zhi Wang, Xiao Feng Sun, Heng Rong Guan, Zhuang Qi Hu
Abstract: Investigation of γ -channel widening behavior in a nickel-base single crystal superalloy during uniaxial tensile creep tests was carried out. Scanning electron microscopy (SEM) was adopted to reveal the microstructural evolution of γ -channel and the dimension of γ -channel. It was found that different tests condition such as temperature, time and stress in tensile creep tests all influenced the γ -channel widening behavior, and a parabolic rate law governs the mean increase value of γ -channel width. The stress and temperature enhanced the γ -channel widening. The γ -channel widening was the result of directionally diffusion of multiatom.
Authors: Xiao Feng Chen, Ying Jun Wang, Na Ru Zhao, Jian Dong Ye, Yu Dong Zheng, Cheng Yun Ning, Gang Wu
Abstract: The biomaterials in system CaO-P2O5-SiO2 were synthesized via sol-gel method. The biomaterials can be applied to bone reparation and bone tissue engineering scaffolds The nano-pore structure, degradability, bioactivity and bio-mineralization characteristic of the biomaterials were investigated in details using XRD, SEM/EDX, FTIR, BET and DSC/TG techniques. It was indicated that the sol-gel derived biomaterials have a higher bioactivity than that of the melt derived bioactive glasses or glass-ceramics. It just takes 4-8 hours for HCA to form on the surface of the sol-gel samples in SBF solution at 37°C. The spherical HCA crystal clusters formed on the surface of the sol-gel derived samples immersed in SBF for 8 hours have a low crystallinity. Owing to their interconnected nano-sized pores, the sol-gel samples possess much higher surface areas and the hydrous porous SiO2 gel layer containing a great amount of ºSi-OH groups can be rapidly formed on the biomterials’ surface through a quick ion exchange between H3O+ in the solution and Ca2+ in the surface of the materials. ºSi-OH groups can play a very important role in inducing formation of HCA. They make the material surfaces electronegative, which resulted in a double electrode layer formed between the samples surface and SBF solution. The double electrode layer is in favor of formation of HCA on the surface of the materials.
Authors: Kai Hui Nan, Ying Jun Wang, Xiao Feng Chen, Na Ru Zhao, L.Y. Wang
Abstract: A porous bioglass reinforced tricalcium phosphate scaffold was prepared. The microstructure, degradability and reaction products of the scaffold after immersed in a simulated body fluid for different days were emphatically investigated using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, Fourier transformed infrared spectroscopy and induced coupled plasma spectroscopy. The results showed that a homogeneous hydroxy-carbonate-apatite (HCA) layer forms on the surface of the scaffold for over 30- day immersion and the oriented growth of the HCA occurs. In addition, this paper discussed the competing mechanism between the dissolution and the precipitation via the measurement of calcium and silicon ionic concentrations in the SBF.
Authors: Cheng Yun Ning, Ying Jun Wang, W.W. Lu, Xiao Feng Chen, Gang Wu, Na Ru Zhao
Abstract: For practical applications such as artifical joints and dental implants, there is a strong demand for hydroxyapatite coatings with excellent performances to ensure long-term fixation. In the present study, functionally gradient HA-ZrO2-Bioglass coatings were prepared using net-energy controlled plasma spraying technology. The structural characteristics andmechanical performances of the coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nanoindentation. The results showed that: (1) Pore sizes and compositions of the coatings changed gradually along the vertical substrate, crystal HA with few calcium phosphates was presented in the heat-treated coatings. (2) Surface of the coating was very rough with nano-sized crystalline grains and micropores; (3) Young’s modulus and hardness changed gradually at the range of coating-Ti6Alo4V interface. Compared with HA coatings, the tensile adhesive strength of the functionally graded HA-ZrO2-Bioglass coatings reached 38.6 MPa, much higher than that of single HA coatings.
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