Papers by Author: Yong Xiang Leng

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Authors: Zhi Hao Wang, Yong Xiang Leng, Nan Huang, Min Hao Zhu
Abstract: Titanium oxides films were deposited on tensile sample and vascular stents made of 316L stainless steel by unbalanced magnetron sputtering. The effects of structures, deposition temperature, Ti interlayer and thickness on the adhesion of titanium oxide films were investigated by tensile tests. The results revealed that the structure of the Ti-O films affect their adhesion dramatically. TiO film is brittle and fragile, lacking ability of deformation. Therefore its adhesion was worse than that of TiO2 film. The higher substrate temperature was helpful to improve adhesion of film, the adhesion of the TiO film deposited at 673K was better than those of the TiO films deposited at 323K and 473K. The adhesion of the TiO film with Ti interlayer was better than the one without interlayer. The introduction of Ti interlayer was beneficial to adhesion of film. The adhesion of thinner TiO2 film was better than that of thicker one. TiO2 film deposited on stents had good adhesion. After expansion, the film didn’t crack and peel off. TiO2 film has potential application on the vascular stents for improving its blood compatibility.
Authors: Feng Juan Jing, Lu Wang, Y.W. Liu, J.Y. Cheng, Yong Xiang Leng, R.K.Y. Fu, X.B. Zhao, Paul K. Chu, Nan Huang
Abstract: Cerium oxide films have been fabricated using dual plasma deposition. X-ray diffraction. (XRD) reveals a crystalline phase and X-ray photoelectron spectroscopy (XPS) shows that La exists predominantly in the +4 oxidation state. The activated partial thromboplastin time is longer than that of blood plasma and stainless steel. Furthermore, the numbers of adhered, aggregated and morphologically changed platelets are reduced compared to low-temperature isotropic carbon (LTIC). HUVEC cells exhibit good adhesion and proliferation behavior on cerium oxide films. This study suggests rare earth oxide films are potential blood-contacting biomedical materials.
Authors: Ji Liang Mo, Min Hao Zhu, J. An, H. Sun, Yong Xiang Leng, Nan Huang
Abstract: CrN coatings were deposited on cemented carbide substrates by filtered cathodic vacuum arc technique (FCVA). The effect of different deposition parameters: nitrogen partial pressure, substrate-bias voltage and preheating of the substrate, on the structural and mechanical properties of the coating was investigated. X-ray diffraction analysis was used to determine the structure and composition of the coatings. The tribological behaviour and wear properties of the coatings against Si3N4 ball at different normal loads were studied under reciprocating sliding condition. The results showed that a smooth and dense CrN coating with good properties can be obtained provided a pure Cr interlayer was pre-deposited. The optimal deposition parameters were the nitrogen partial pressure of 0.1 Pa, substrate-bias voltage of -100 V. Preheating of the substrate was no good for improving the properties of the coating. The FCVA CrN coating showed high hardness and good wear resistance, which was probably attributed to its smooth surface and dense microstructure. The wear mechanism of the CrN coating was a combination of abrasion and oxidation. However, the coating flaked off at high normal load due to the deficient adhesion strength of the coating to the substrate.
Authors: Lan Xin Xu, Peng Li, Jin Wang, Yong Xiang Leng, Hong Sun, Guang Jun Cai, Nan Huang
Abstract: In order to improve the abrasion property of polyoxymethylene (POM),diamond like carbon (DLC) film was deposited on POM substrate by the method of magnetic filtered cathodic vacuum arc deposition (MFCVAD). X-ray photoelectron spectroscopy (XPS) showed that the sp3 fraction decreased with the negative bias voltages increased. According to the result of the nano-indenter, the hardness of POM plates coated with DLC films was significantly harder than POM substrate. The results of ball-on-disc tribological testing demonstrated that the hardest DLC film had the lowest friction coefficient (0.11). The evaluation of in vitro platelet adhesion test indicates that the numbers of adhered and activated platelet on the DLC film deposited under the condition of 0V and 9min were remarkably decreased compared with that of the untreated POM.
Authors: Jin Biao Wang, Ping Yang, Gui Cai Li, Zhong Hai Yang, Yong Xiang Leng, Hong Sun, Nan Huang
Abstract: For an application as biomedical materials of high performance with a good biocompatibility, the Ti-O film on Si (110) wafer substrate has been synthesize by means of unbalance reactive magnetron sputtering method and modified by phosphorus ion implantation and succeeding vacuum annealing. X-ray diffraction (XRD) results indicated that such prepared Ti-O film had a rutile structure. X-ray photoelectron spectroscopy (XPS) analysis demonstrates the effect of P ion doping. The contact angle test and sheet resistance results showed that titanium oxide film and phosphorus-doped titanium oxide film became more hydrophilic and higher conductance after annealing. The morphology and roughness of the surface have been investigated using SEM. Antithrombotic property of the titanium oxide thin film was examined by platelet adhesion tests. The results showed that the undoped Ti-O films and the P implant and annealing at 900 °C Ti-O film had good blood compatibility.
Authors: Feng Juan Jing, Nan Huang, Jun Ying Chen, Yong Xiang Leng, H. Sun
Abstract: Aminopropyltriethoxysilane (APTE) was covalently interacted with hydroxyl on the surface of Ti-O films prepared by magnetron sputtering, and albumin and heparin were immobilized on the APTE-coated surface with addition of 1-ethyl-3- (3-dimethyl aminopropyl) carbodiimide (EDC) as cross-link agent. X-ray photoelectron spectroscopy (XPS) was used to investigate the modified surface. Contact angle results indicate that there was an increase in the contact angle to the surface of APTE-coated Ti-O films, and a decrease in the contact angle to the surface of albuminand heparin-immobilized surfaces. Blood platelet adhesion in vitro was improved significantly after immobilization of albumin and heparin on Ti-O films. Endothelial cell (EC) culture tests showed that EC could grow on the surface of Ti-O films immobilized with albumin and heparin, but the growth and proliferation behavior of endothelial cells was not as good as on naked Ti-O films. This investigation showed that the surface of bio-inert inorganic materials immobilized with biological molecules is feasible and effective for improving the blood compatibility.
Authors: Nan Huang, Ping Yang, Yong Xiang Leng, Jun Ying Chen, Jin Wang, Guo Jiang Wan, Hong Sun, X. Wu, An Sha Zhao
Abstract: This paper presents recent activities on the surface modification of blood contacting biomaterials and devices in the author’s laboratory. Surface coating of inorganic films on materials for artificial heart valves, ventricular pumps and coronary stents, such as titanium, stainless steel and low temperature isotropic pryolitc carbon, etc, shows a significant improvement in the anticoagulation behavior. Further, the formation of functional groups such as hydroxyl or amino groups and the binding of biomolecules as well as seeding of endothelial cell shows the promise of biomimetic surface formation. Plasma grafting on materials for artificial heart valve sewing cuff, extracorporeal circulation tube, etc, such as PET, PU, PVC polymers, revealed a significant improvement of anti-platelet adhesion as well as anti-bacterial properties.
Authors: Bo Feng, Jie Weng, Shao Xing Qu, Yong Xiang Leng, Zhong Rong Zhou
Abstract: Influence of heat-treatment conditions on wear resistance of titanium was investigated. Titanium plates were subjected to heat-treatment in air and water vapor respectively. Heat-treatments increased micro-hardness of titanium. The plate heat-treated in air (H) has the highest roughness and the plate treated in water vapor (W) lowest. After heat-treatment surface oxide was rutile. The friction coefficient of W was the lowest and almost stable at about 0.18. Non-heat--treated titanium plate (S) had a highest coefficient up to 1.1. Wear resistance of heat--treated titanium, especially W was significantly superior to non-treated titanium. The wear of S resulted mainly from adhesion failure, H involved with abrasive wear and fatigue failure. For W, a complex wear mechanism was probably existed.
Authors: An Sha Zhao, Ping Yang, Yong Xiang Leng, Jun Ying Chen, Jin Wang, Guo Jiang Wan, Nan Huang
Abstract: Ti-O film is a kind of potential biomaterial may be applied in medical devices. But the mechanism of its good biocompatility is not so clear. This study revealed that when Titanium oxide contact with macrophage and plasma, the activation, adhesion and secretion of inflammatory molecule MCP-1 of macrophage is lower than reference material. Ti-O film also show minor contact activation to plasma. So reducing the host reaction including contact activation and inflammation may be the important reason for the good biocompatibility of Ti-O film.
Authors: An Sha Zhao, Gui Cai Li, Ping Yang, Yong Xiang Leng, Jun Ying Chen, Jin Wang, Guo Jiang Wan, Nan Huang
Abstract: Macrophages play a critical role in inflammatory response to implanted biomaterials and formation of restenosis. Macrophage adhesion may lead to macrophage activation and smooth muscle cell proliferation. Titanium oxide films on stainless steel are potential biomaterials for application to vascular stents. They have different influences on smooth muscle cell proliferation in in vivo tests, which could be the main reason for restenosis, but the mechanism is not clear. In this study we show that titanium oxide films can reduce inflammatory reaction with macrophages. Unstimulated macrophages release small amounts of chemical substance such as NO and give slight effect on smooth muscle cell proliferation.
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