Co-reporter:Junlei Li, Lili Tan, Peng Wan, Xiaoming Yu, Ke Yang
Materials Science and Engineering: C 2015 Volume 49() pp:422-429
Publication Date(Web):1 April 2015
DOI:10.1016/j.msec.2015.01.029
•The extruded NZ20 alloy appeared fine-grained and globular.•A lot of fine granular particles were observable in the E1 sample.•Both E1 and E2 presented excellent plasticity.•Compared with E2, E1 exhibited a relatively lower corrosion rate.Mg–2Nd–0.2Zn (NZ20) alloy was prepared for the application as biodegradable implant material in this study. The effects of the extrusion process on microstructure, mechanical and corrosion properties of the alloy were investigated. The as-cast alloy was composed of α-Mg matrix and Mg12Nd eutectic compound. The solution treatment could lead to the Mg12Nd phase dissolution and the grain coarsening. The alloy (E1) preheated at 380 °C for 1 h and extruded at 390 °C presents fine grains with amounts of tiny Mg12Nd particles uniformly dispersed throughout the boundaries and the interior of the grains. The alloy (E2) preheated at 480 °C for 1 h and extruded at 500 °C exhibits relatively larger grains with few nano-scale Mg12Nd phase particles dispersed. The alloy of E1, compared with E2, showed relatively lower corrosion rate, higher yield strength and slightly lower elongation.
Co-reporter:Lili Tan, Qiang Wang, Xiao Lin, Peng Wan, Guangdao Zhang, Qiang Zhang, Ke Yang
Acta Biomaterialia 2014 Volume 10(Issue 5) pp:2333-2340
Publication Date(Web):May 2014
DOI:10.1016/j.actbio.2013.12.020
Abstract
In this study the loss of mechanical properties and the interface strength of coated AZ31B magnesium alloy (a magnesium–aluminum alloy) screws with surrounding host tissues were investigated and compared with non-coated AZ31B, degradable polymer and biostable titanium alloy screws in a rabbit animal model after 1, 4, 12 and 21 weeks of implantation. The interface strength was evaluated in terms of the extraction torque required to back out the screws. The loss of mechanical properties over time was indicated by one-point bending load loss of the screws after these were extracted at different times. AZ31B samples with a silicon-containing coating had a decreased degradation rate and improved biological properties. The extraction torque of Ti6Al4V, poly-l-lactide (PLLA) and coated AZ31B increased significantly from 1 week to 4 weeks post-implantation, indicating a rapid osteosynthesis process over 3 weeks. The extraction torque of coated AZ31B increased with implantation time, and was higher than that of PLLA after 4 weeks of implantation, equalling that of Ti6Al4V at 12 weeks and was higher at 21 weeks. The bending loads of non-coated AZ31B and PLLA screws degraded sharply after implantation, and that of coated AZ31B degraded more slowly. The biodegradation mechanism, the coating to control the degradation rate and the bioactivity of magnesium alloys influencing the mechanical properties loss over time and bone–implant interface strength are discussed in this study and it is concluded that a suitable degradation rate will result in an improvement in the mechanical performance of magnesium alloys, making them more suitable for clinical application.
Co-reporter:Xiao Lin, Xiaoming Yang, Lili Tan, Mei Li, Xin Wang, Yu Zhang, Ke Yang, Zhuangqi Hu, Jianhong Qiu
Applied Surface Science 2014 Volume 288() pp:718-726
Publication Date(Web):1 January 2014
DOI:10.1016/j.apsusc.2013.10.113
Highlights
- •
Strontium element was incorporated into the phosphate MAO coatings.
- •
The degradation of MAO coating was accompanied with the CaP deposition.
- •
A degradation model of the phosphate MAO coating was proposed.
- •
The biocompatibility/bioactivity was enhanced by the incorporation of strontium.
Co-reporter:Chen Liu, Huazhe Yang, Peng Wan, Kehong Wang, Lili Tan, Ke Yang
Materials Science and Engineering: C 2014 Volume 35() pp:1-7
Publication Date(Web):1 February 2014
DOI:10.1016/j.msec.2013.10.020
•Degradation of Mg17Al12 was investigated via experiment and calculations.•Normal and inflammatory response environment were simulated with different pH.•Degradation mechanism of Mg17Al12 second phase and magnesium matrix was discussed.The in vitro biodegradation behavior of Mg17Al12 as a second phase in Mg–Al–Zn alloys was investigated via electrochemical measurement and immersion test. The Hank's solutions with neutral and acidic pH values were adopted as electrolytes to simulate the in vivo environment during normal and inflammatory response process. Furthermore, the local orbital density functional theory approach was employed to study the thermodynamical stability of Mg17Al12 phase. All the results proved the occurrence of pitting corrosion process with crackings for Mg17Al12 phase in Hank's solution, but with a much lower degradation rate compared with both AZ31 alloy and pure magnesium. Furthermore, a preliminary explanation on the biodegradation behaviors of Mg17Al12 phase was proposed.
Co-reporter:Junlei Li, Feng Zheng, Xun Qiu, Peng Wan, Lili Tan, Ke Yang
Materials Science and Engineering: C 2014 Volume 42() pp:705-714
Publication Date(Web):1 September 2014
DOI:10.1016/j.msec.2014.05.078
•A 3D FEA model of MAS model was proposed.•The strain can be decreased by adding a peak-to-valley unit to the stent.•The mechanical behavior of the stent can be optimized by the gradual strut.•The annealing technology helps to decrease the residual stress of the stent.•Experiments were carried out for a preliminary validation of the simulation.Stents made of biodegradable magnesium alloys are expected to provide a temporary opening into a narrowed arterial vessel until it remodels and will progressively disappear thereafter. Inferior mechanical properties and fast corrosion of the magnesium alloys are the two crucial factors that impede the clinical application of the magnesium alloy stents (MAS). In the present study, gradual strut width, addition of the peak-to-valley unit and introduction of the annealing technology were designed and investigated by finite element analysis in order to improve the performance of the MAS. Two experiments were carried out for a preliminary validation of the simulation.
Co-reporter:Qiang Zhang, Xiao Lin, Zhengrong Qi, Lili Tan, Ke Yang, Zhuangqi Hu, Yan Wang
Journal of Materials Science & Technology 2013 Volume 29(Issue 6) pp:539-544
Publication Date(Web):June 2013
DOI:10.1016/j.jmst.2013.03.003
Bone graft substitutes are widely-studied as alternatives to bone grafts in the clinic. The currently available products are mostly ceramics and polymers. Considerable progress has been made in the study of the biodegradable magnesium alloys, which possess the necessary attributions of a suitable substitute, including an excellent mechanical property. In the present study, a minipig model of a lateral tibial plateau defect was used to evaluate the effectiveness of a magnesium alloy in the repair of a critical-sized defect. The micro-arc oxidation (MAO)-coated ZK60 alloy tablets and medical-grade calcium sulfate pellets were used as the test and control materials, respectively. Bone morphology was monitored by computed tomography after the implantation for 2 and 4 months. It was found that the bone morphology in minipigs following magnesium treatment was similar to that of the normal bone, whereas an abnormal and concave morphology was displayed following the calcium sulfate treatment. The average bone healing rate for the magnesium-treated defects was higher than that of the calcium sulfate-treated defects at the first 4 months following the implantation. Overall, magnesium treatment appeared to improve the defect repair as compared with the calcium sulfate treatment. Thus, the MAO-coated ZK60 alloy appears to be a useful biocompatible bone graft substitute, and further research on its biological activity in vivo is needed.
Co-reporter:Chen Shanshan, Tan Lili, Teng Yingxue, Zhang Bingchun, Yang Ke
Materials Science and Engineering: C 2013 Volume 33(Issue 3) pp:1476-1480
Publication Date(Web):1 April 2013
DOI:10.1016/j.msec.2012.12.049
Drug-eluting stent has been proved to decrease the restenosis caused by the stent implantation, owing to the existence of a drug-eluting coating on the stent. For ensuring the effectivity and security of the drug-eluting stent during the service period, the uniform surface, good deformation and stabilized drug release behavior of the stents should be satisfied. In this study, the performances mentioned were studied on stainless steel stents. The results showed that the surface morphology of the coating was affected by the sorts of solvent, the parameters of the spraying process and the addition of the plasticizer. The drug-eluting profile of the coating was influenced by the plasticizer content and PLGA/drug ratio of the coating. Meanwhile, the plasticizer as an additional agent obviously increased the deformation performance of the coating. Optimized parameters for preparation of the drug-eluting coating were investigated to obtain a drug-eluting coating with good integrated performances.Highlights► How the spray parameters control the quality of coating was systematically studied. ► PEG increased the coating deformation ability and affected the drug-eluting profile. ► Proper increase of polymer/drug ratio could avoid the drug burst releasing. ► Uniform surface, good deformation and stabilized drug release profiles were obtained. ► Relevance between spray process and surface, deformation, drug release was studied.
Co-reporter:Ling Ren, Xiao Lin, Lili Tan, Ke Yang
Materials Letters 2011 Volume 65(23–24) pp:3509-3511
Publication Date(Web):December 2011
DOI:10.1016/j.matlet.2011.07.109
Antibacterial behaviors of magnesium (Mg) based metal, pure Mg and AZ31 alloy, with and without surface coatings were studied. The results indicated that both pure Mg and AZ31 alloy had strong antibacterial effect against Escherichia coli and Staphylococcus aureus with rapid increases of pH values of the bacterial suspensions. Pure Mg with porous silicon-contained (Si) coating by micro-arc oxidation still maintained its antibacterial ability while with a mild increase of the pH value. However, pure Mg and AZ31 alloy with fluorine-contained (F) and Si coatings by chemical conversion, respectively, lost their antibacterial abilities with nearly no change of the pH values, owing to the much dense coatings on surfaces.Highlights► Mg based metals, pure Mg and its alloys possess antibacterial functions. ► Antibacterial functions of Mg based metals are related to the increase of pH. ► Surface coating on Mg based metals can affect their antibacterial abilities. ► Loose and porous coating on Mg could maintain its antibacterial ability. ► Dense coating on Mg and its alloy could lose its antibacterial ability.
Co-reporter:Tingting Yan, Lili Tan, Dangsheng Xiong, Xinjie Liu, Bingchun Zhang, Ke Yang
Materials Science and Engineering: C 2010 30(5) pp: 740-748
Publication Date(Web):
DOI:10.1016/j.msec.2010.03.007
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2_b.png)
