下载文档原格式
高性能多孔β-磷酸三钙骨组织工程支架的3D打印袁景;甄平;赵红斌【摘要】背景：虽然采用溶液浇铸/离子洗出法、原位成型法、静电纺丝法、相分离/冻干法、气体成孔法等制备骨组织工程支架可以获得比较满意的效果，但在精确性、孔隙均匀性、空间结构复杂性、支架个性化等方面略显不足。
<br> 目的：利用3D打印制备β-磷酸三钙骨组织工程支架。
<br> 方法：利用3D打印制备载药β-磷酸三钙支架，观察其结构，测量其孔隙率和力学强度。
将载药β-磷酸三钙支架置入模拟体液中15周，观察其质量变化。
将载药β-磷酸三钙支架与大鼠骨髓间充质干细胞共培养7 d，观察细胞黏附与形态变化。
分别采用载药β-磷酸三钙支架浸提液与含体积分数15%胎牛血清的低糖 DMEM培养基培养大鼠骨髓间充质干细胞，培养24，48，72 h检测细胞A值，并确定细胞毒性分级；同时成骨诱导培养1周，检测两组细胞碱性磷酸酶活性。
<br> 结果与结论：实验制备的支架微观孔隙呈不规则形，孔隙率高，孔隙分布均匀，孔隙连通率高，抗压强度大。
载药β-磷酸三钙支架在15周内基本降解完全，与松质骨缺损修复时间相当。
大鼠骨髓间充质干细胞黏附于载药β-磷酸三钙支架表面，并深入支架内部，生长良好，增殖活跃，细胞碱性磷酸酶活性有提高，说明载药β-磷酸三钙支架具有良好的细胞相容性。
%BACKGROUND:Although the preparation of bone tissue engineering scaffolds can achieve satisfactory results by solvent casting/particulate leaching, in situ molding method, electrospinning, phase seperation/freeze drying, gas foaming, there are stil some deficiencies in the accuracy, pore uniformity, spatial structure complexity, personalized stents. <br> OBJECTIVE:To prepareβ-tricalcium phosphate bone tissue engineering scaffolds using 3D printing. <br>METHODS:Drug-loadedβ-tricalcium phosphate scaffolds were prepared with 3D printing, and the structure was observed to measure its porosity and mechanical strength. The scaffold was immersed in simulated body fluid for 15 weeks to observe the quality change. The scaffold was co-cultured with rat bone marrow mesenchymal stem cells for 7 days to observe celladhesion and morphological changes. Rat bone marrow mesenchymal stem cells were cultured in extracts of drug-loadedβ-tricalcium phosphate scaffold and low-glucose Dulbecco's modified Eagle’s medium containing 15%fetal bovine serum for 24, 48, and 72 hours, to determine the absorbance values and cytotoxicity grading, respectively. Meanwhile, the cells were subjected to osteogenic culture for 1 week, and <br> the alkaline phosphatase activities in two groups were detected. <br> RESULTS AND CONCLUSION:The prepared scaffold showed irregular micropores, high porosity, uniform pore distribution, high pore connectivity rate, and large compressive strength. The drug-loadedβ-tricalcium phosphate scaffold degraded completely with 15 weeks, and cancellous bone defect repair was completed in the same period. Rat bone marrow mesenchymal stem cells adhered to the surface of drug-loadedβ-tricalcium phosphate scaffold and went deep into the scaffold, showing good growth and proliferation. The activity of alkaline phosphatase was also improved. These findings indicate that the drug-loadedβ-tricalcium phosphate scaffold has good biocompatibility.【期刊名称】《中国组织工程研究》【年(卷),期】2014(000)043【总页数】8页(P6914-6921)【关键词】生物材料;骨生物材料;孔隙率;抗压强度;细胞相容性;有限元分析;国家自然科学基金【作者】袁景;甄平;赵红斌【作者单位】解放军兰州军区总医院全军骨科中心，甘肃省兰州市 730050; 甘肃中医学院研究生院，甘肃省兰州市730030;解放军兰州军区总医院全军骨科中心，甘肃省兰州市 730050;解放军兰州军区总医院全军骨科中心，甘肃省兰州市730050【正文语种】中文【中图分类】R318文章亮点：1 制备骨组织工程支架以往常采用溶液浇铸/离子洗出法、原位成型法、静电纺丝法、相分离/冻干法、气体成孔法等，这些制备方法获得了比较满意的效果，但在精确性、孔隙均匀性、空间结构复杂性、支架个性化等方面不尽人意。
文章编号:1001-9731(2021)01-01022-04镁合金表面微弧氧化陶瓷涂层的制备及耐蚀性能*余灏勋,马廷霞(西南石油大学机电工程学院,成都610500)摘要:利用微弧氧化法,在微弧氧化反应电解质中加入氟钛酸钾和G R/T i O2粉末,在镁合金表面制备了MA O-G R/T i O2涂层㊂采用S E M和F T-I R分别对G R/T i O2粉末的表面形貌和结构进行了研究,用S E M㊁X R D 和元素线扫描对MA O-G R/T i O2涂层的表面形貌㊁相结构和元素分布进行了研究,用三电极技术对MA O-G R/T i O2涂层的耐腐蚀性能进行了研究㊂结果表明,通过溶胶-凝胶法可将纳米T i O2接枝到G O表面,生成G R/T i O2粉末;MA O-G R/T i O2涂层主要由M g2T i O4相㊁M g3(P O4)2相㊁M g和M g O相组成;以界面为分界线,涂层一侧T i㊁P和O元素高于基体一侧,基体一侧M g元素高于涂层一侧;MA O-G R/T i O2涂层的腐蚀电位为-0.723V,腐蚀电流密度为8.96ˑ10-8A/c m2,相比镁合金基体和MA O涂层,腐蚀电位提高了48.3%和36.7%,表明MA O-G R/T i O2涂层可以显著提高镁合金基体的耐蚀性能㊂关键词:镁合金;微弧氧化法;复合涂层;耐腐蚀性能中图分类号: T B332文献标识码:A D O I:10.3969/j.i s s n.1001-9731.2021.01.0040引言镁合金耐蚀性差严重限制了其在许多领域的应用[1-2]㊂目前为止,研究者广泛研究的耐腐蚀方法是在合金表面形成防腐涂层㊂微弧氧化技术(MA O)是在常规阳极氧化技术基础上发展起来的一种新型的镁合金表面处理技术,该技术可以制造高质量的涂层,具有高硬度值,强附着力,并可以大幅提高镁合金基体的耐腐蚀性[3]㊂因此,MA O已经成为提高镁合金耐蚀性研究最热门的技术之一[4-6]㊂MA O涂层的耐蚀性主要取决于涂层的厚度㊁成分和组织结构[7]㊂根据已有的研究,电解液的组成会影响涂层的微观结构㊁成分和性能,因为这些元素可以在氧化过程中掺杂入涂层中[8-9]㊂几种类型的电解质,如硅酸盐[10]㊁铬酸盐[11]和磷酸盐[12],已被用于制备MA O涂层㊂一般来说,在这些电解质中形成的MA O涂层主要由M g O相和其它一些与电解质有关的化合物组成[如M g O㊁M g3-(P O4)2㊁M g A l2O4或M g F2][13]㊂由于M g O在中性或酸性环境中不稳定,这些涂层不能提供足够的长期腐蚀保护㊂解决该问题最有效的办法是通过改变电解质的组成,在MA O涂层中加入稳定氧化物或其它稳定化合物,如N b2O5㊁Z r O2㊁T i O2㊁M g2Z r5O12㊁C e O2㊁M g F2或Z r F4㊂这些氧化物和化合物可以在氧化处理过程中嵌入到涂层中,以提高涂层的耐蚀性[14]㊂然而,在这些电解液中,有许多化合物不能长期使用(相对不稳定),因为在微弧氧化过程中,试样表面预先形成了小的火花,不能得到均匀的MA O涂层[15]㊂石墨烯(G R)和氧化石墨烯(G O)具有优异的力学和耐腐蚀性能,不仅力学强度高,而且耐磨性优异[16-17]㊂T i O2颗粒具有优异的耐腐蚀性能[18-20]㊂本文以氟钛酸钾(K2T i F6)㊁六偏磷酸钠[(N a P O3)6]㊁氢氧化钠(N a O H)和三乙胺(T E A)组成的合适电解质,制备了含有M g2T i O4和G R/T i O2的MA O-G R/T i O2涂层㊂采用X R D㊁S E M和元素线扫描等手段研究了涂层的相结构㊁表面形貌和元素组成,并采用电化学阻抗法评价了涂层的耐蚀性㊂1实验1.1 G R/T i O2粉末的制备采用加压氧化法合成G O,采用溶胶-凝胶法制备G R/T i O2粉末㊂由于G O的亲水性和静电斥力,在水中形成了稳定的溶胶㊂具体制备方法:取5m L钛酸丁酯,与10m L冰乙酸均匀混合,然后加入30m L无水酒精进行稀释,分散搅拌均匀30m i n后得到溶液A;将G O超声分散在15m L蒸馏水中,超声浴2h,随后加入15m L无水酒精,并用稀硝酸调节p H值至2,得到溶液B㊂将溶液B缓慢加入到溶液A中,并在室温下搅拌3h,并陈化得到凝胶,随后将凝胶转入水热反应釜中,210ħ下恒温反应10h后自然冷却至室温,用去离子水将所得产物洗涤至中性,并烘干,即得到G R/T i O2粉末㊂220102021年第1期(52)卷*基金项目:四川省科技计划资助项目(18F Z J C00734)收到初稿日期:2020-06-03收到修改稿日期:2020-09-23通讯作者:马廷霞,E-m a i l:1499893831@q q.c o m 作者简介:余灏勋(1994 )男,成都人,硕士,主要从事新型复合材料制备研究㊂1.2复合涂层的制备将A Z31合金(M g-3%(质量分数)A l-0.8%(质量分数)Z n)试样切割成10mmˑ10mmˑ5mm,用100~1000#的S i C砂纸打磨㊂然后分别在乙醇和去离子水中超声清洗20m i n,最后在空气中干燥㊂采用功率为2k W的恒流电源,通过MA O法制备涂料㊂分别以镁合金基体和不锈钢板作为工作电极和对电极㊂为了制备含有G R/T i O2的MA O涂层,采用以下磷酸盐电解质进行一次处理:即由15g/L氟钛酸钾(K2T i F6),20g/L六偏磷酸钠[(N a P O3)6], 10g/L氢氧化钠(N a O H),3g/L G R/T i O2粉末和0.3g/L三乙胺(T E A)组成的电解质,使G R/T i O2粉末带负电荷,然后将电解质超声处理1h,随后连接电极,并将电极放入电解质中㊂两个电极之间的距离为2c m,在400V的固定外加电压下进行10m i n的一次微弧氧化反应㊂得到的复合涂层标记为MA O-G R/ T i O2涂层㊂采用相同的MA O工艺(磷酸盐电解质中没有G R/T i O2)制备的M g合金作为对照组,标记为MA O涂层㊂1.3样品的表征采用T T R I I IX射线衍射仪对制备的涂层相组成进行了X射线衍射分析,2θ值在10~85ʎ之间,步长增量为0.01ʎ,扫描速度为4ʎ/m i n;采用N I C O L E T F T-I R5700光谱仪对G O㊁G R/T i O2粉末及复合涂层进行F T-I R光谱测试;采用德国蔡司(型号:S U P R A-55)扫描电子显微镜对G R/T i O2粉末和复合涂层的表面形貌及元素组成进行研究㊂1.4电化学测量采用三电极技术在电化学工作站(C H I660E)上进行动电位极化实验㊂以复合涂层样品为工作电极,铂板为对电极,饱和甘汞电极(S E C)为参比㊂所有测试都在(37ʃ1)ħ的3.5%(质量分数)氯化钠溶液中进行㊂用1c m2的硅胶覆盖所有样品暴露的表面㊂在溶液中稳定1h后进行动电位极化试验,以确保开路电位是静态的㊂电位扫描速度为5m V/s,记录极化曲线㊂E I S的信号幅度为5m V,频率为0.01~ 10000H z㊂采用T a f e l外推和线性极化法,从动电位极化图中获取腐蚀电位(E c o r r)和腐蚀电流密度(i c o r r)㊂本文选择性地展示了极化曲线,所展示的极化曲线数据最接近每组样本的平均值㊂2结果与讨论2.1 G O和G R/T i O2粉末的表征2.1.1 F T-I R分析图1为G O和G R/T i O2粉末的F T-I R光谱图㊂由图1可知,G O曲线中3395c m-1处的宽吸收峰为-O H伸缩振动峰,2358c m-1处的伸缩振动对应C-O 键,1733c m-1处的伸缩振动对应C=O键, 1621c m-1位置的伸缩振动对应C=C键,1222c m-1位置的伸缩振动对应C-O-C键,1057c m-1位置的伸缩振动对应C-O H键;G R/T i O2曲线中,535c m-1处的吸收峰对应T i-O-T i键,而1733,1222和1057c m-1处峰强的减弱,说明G O在反应过程中被还原成了G R ㊂图1 G O和G R/T i O2粉末的F T-I R光谱图F i g1F T-I Rs p e c t r a o fG Oa n dG R/T i O2p o w d e r2.1.2S E M分析图2为G O和G R/T i O2粉末的S E M图㊂从图2 (a)可以看出,G O为片状多层结构,具有许多类似于波动丝绸的褶状㊂从图2(b)可以看出,T i O2颗粒分散在G R的片状表面,大部分G R表面可以被T i O2颗粒包裹住,颗粒大小为纳米级,表明T i O2纳米粒子可以成功地接枝到G R表面㊂图2 G O和G R/T i O2粉末的S E M图F i g2S E Mi m a g e s o fG Oa n dG R/T i O2p o w d e r s2.2 MA O-G R/T i O2涂层的表征2.2.1 X R D和元素线扫描分析图3为MA O-G R/T i O2涂层的X R D图谱㊂由图3可知,涂层X R D图谱中可以明显观察到18.6ʎ和29.5ʎ处的M g2T i O4对应峰;此外,还可以观察到明显的M g3(P O4)2㊁M g和M g O的对应峰,但是并未发现典型的T i O2峰,可能是因为T i O2峰和M g2T i O4峰有一定重叠而被掩盖,也有可能是T i O2含量太少㊂图4为MA O-G R/T i O2涂层截面元素的线扫描分析㊂从图4可以看出,以界面为分界线,涂层一侧T i㊁P和O元素高于基体一侧,基体一侧M g元素高于涂层一侧,而基体一侧A l元素只稍微高于涂层一侧,区别并不明显㊂这一元素分布和图3中MA O-G R/ T i O2涂层X R D图谱测试结果正好吻合㊂32010余灏勋等:镁合金表面微弧氧化陶瓷涂层的制备及耐蚀性能图3 MA O -G R /T i O 2涂层的XR D 图谱F i g 3X R D p a t t e r no fMA O -G R /T i O 2co a t i ng 图4 MA O -G R /T i O 2涂层截面元素的线扫描分析F i g 4L i n e s c a n n i n g a n a l ys i s o f s e c t i o n a l e l e m e n t s o f MA O -G R /T i O 2co a t i n g 2.2.2 S E M 分析图5展示了镁合金基体上MA O 和MA O -G R/T i O 2涂层的SE M 形貌㊂从图5可以看出,由于涂层生长不均匀,MA O 生长过程中会捕获熔融氧化物和气泡,MA O 涂层和MA O -G R /T i O 2涂层的表面均存在圆形孔隙通道,这是电解质与M g 合金基体接触的通道㊂由于在相对冷的电解质中,熔融氧化物是从数千度的温度下快速冷却的,所以在MA O 涂层和MA O -G R /T i O 2涂层上表面粗糙,并可以观察到微小裂纹㊂MA O -G R /T i O 2涂层表面并未观察到明显的G R /T i O 2材料,只是相比MA O ,表面更加粗糙㊂图5 MA O 和MA O -G R /T i O 2涂层的S E M 图F i g 5S E Mi m a g e s o fMA Oa n dMA O -G R /T i O 2co a t -i n gs 2.3 腐蚀行为评价图6为镁合金基体㊁M A O 涂层和M A O -G R /T i O 2涂层在N a C l 溶液中的典型动电位极化曲线㊂根据T a f e l 外推和线性极化法提取了电化学参数的平均值,结果如表1所示㊂由图6和表1可知,与镁合金基体相比,M A O 涂层和M A O -G R /T i O 2涂层都提高了腐蚀电位,说明涂层的稳定性和有效性优于镁合金基体㊂M A O -G R /T i O 2涂层的腐蚀电位相比镁合金基体和M A O 涂层,提高了48.3%和36.7%㊂这些结果表明,M A O -G R /T i O 2涂层可以显著提高M g 合金基体的耐蚀性能㊂图6 镁合金基体㊁MA O 涂层和MA O -G R /T i O 2涂层在Na C l 溶液中的动电位极化曲线F i g 6P o t e n t i o d yn a m i c p o l a r i z a t i o nc u r v e s o f m a g n e s i u m a l l o y ma t r i x ,MA O c o a t i n g a n d MA O -G R /T i O 2co a t i n g i nN a C l s o l u t i o n表1 镁合金基体㊁MA O 涂层和MA O -G R /T i O 2涂层材料的腐蚀特性分析结果T a b l e1A n a l ys i sr e s u l t so fc o r r o s i o nc h a r a c t e r i s t i c s o f m a g n e s i u m a l l o y m a t r i x ,MA O c o a t i n ga n dMA O -G R /T i O 2co a t i n g i nN a C l s o l u t i o n 试样腐蚀电位/V 腐蚀电流密度/A ㊃c m -2镁合金基体-1.3981.59ˑ10-5MA O 涂层-1.1423.12ˑ10-7MA O -G O /T i O 2涂层-0.7238.96ˑ10-83 结 论(1)通过溶胶-凝胶法可将纳米T i O 2接枝到GO 表面,但是接枝过程中,G O 被还原成了G R ,生成了G R /T i O 2粉末材料㊂(2)MA O -G R /T i O 2涂层主要由M g 2T i O 4相㊁M g 3(P O 4)2相㊁M g 和M g O 相组成㊂以界面为分界线,涂层一侧T i ㊁P 和O 元素高于基体一侧,基体一侧M g 元素高于涂层一侧,而基体一侧A l 元素只稍微高于涂层一侧㊂(3)MA O -G R /T i O 2涂层的腐蚀电位为-0.723V ,腐蚀电流密度为8.96ˑ10-8A /c m 2,相比镁合金基体和MA O 涂层,腐蚀电位提高了48.3%和36.7%,表明MA O -G R /T i O 2涂层可以显著提高镁合金基体的耐蚀性能㊂参考文献:[1] G u oK W.Ar e v i e wo fm a g n e s i u m /m a g n e s i u ma l l o ys c o r -420102021年第1期(52)卷r o s i o n [J ].R e c e n tP a t e n t so n C o r r o s i o nS c i e n c e ,2011,1(1):72-90.[2] Y a n g K H ,G e rM D ,H w uW H ,e t a l .S t u d y of v a n a d i u m -b a s e d c h e m i c a l c o n v e r s i o n c o a t i ng on t h e c o r r o s i o n r e s i s t -a n c e o fm a g n e s i u ma l l o y [J ].M a t e r i a l sC h e m i s t r y &P h ys -i c s ,2015,101(2-3):480-485.[3] H u a n g YS ,L i uH W.T E Ma n a l y s i s o nm i c r o -a r c o x i d e c o a t i n go n t h e s u r f a c e o fm a g n e s i u ma l l o y[J ].J o u r n a l o fM a t e r i a l sE n -g i n e e r i n g &Pe rf o r m a n c e ,2011,20(3):463-467.[4] J i a ng BL ,G eYF .M i c r o -a r c o x i d a t i o n (M A O )t o i m pr o v e t h e c o r r o s i o n r e s i s t a n c eo fm a g n e s i u m (M g )a l l o ys [J ].C o r r o s i o n P r e v e n t i o n o fM a g n e s i u m A l l o ys ,2013:163-196.[5] W a n g S ,L i uP .T h e t e c h n o l o g y o f p r e p a r i n gg r e e nc o a t i n gb yc o nd u c t i n g m i c r o -a r co x i d a t i o no n A Z 91D m a gn e s i u m a l l o y [J ].P o l i s hJ o u r n a l o fC h e m i c a lT e c h n o l o g y ,2016,18(4):36-40.[6] L iY ,L uF ,L iH L ,e t a l .C o r r o s i o n m e c h a n i s mo fm i c r o -a r co x i d a t i o nt r e a t e db i o c o m p a t i b l eA Z 31m a gn e s i u m a l -l o y i ns i m u l a t e db o d y f l u i d [J ].P r o gr e s s i n N a t u r a lS c i -e n c e :M a t e r i a l s I n t e r n a t i o n a l ,2014,24(5):516-522.[7] N i eR R ,Z h uF ,S h e nL R ,e t a l .E f f e c t so f f i l mt h i c k n e s so n t h e p h a s e c o m p o s i t i o n a n dm i c r o s t r u c t u r e p r o pe r t i e s of m i c r o -a r c o x i d a t i o n c o a t i ng [J ].J o u r n a l o fB i o m e d i c a lE n -g i n e e r i n g,2010,27(2):354-357.[8] Y a n g W ,X uD P ,G u oQ Q ,e t a l .I n f l u e n c eo f e l e c t r o l yt e c o m p o s i t i o no n m i c r o s t r u c t u r ea n d p r o p e r t i e so f c o a t i n gs f o r m e do n p u r eT i s u b s t r a t eb y mi c r oa r co x i d a t i o n [J ].S u r f a c e&C o a t i n g sT e c h n o l o g y,2018,349:522-528.[9] P a kSN ,Y a oZP ,J uKS ,e t a l .E f f e c t o f o r ga n i c a d d i t i v e s o n s t r u c t u r e a n d c o r r o s i o n r e s i s t a n c e o fMA Oc o a t i n g[J ].V a c u u m ,2018,151:8-14.[10] Z h a n g R F ,X i o n g G Y ,H uC Y.C o m p a r i s o no f c o a t i n gp r o p e r t i e so b t a i n e db y MA Oo nm a g n e s i u ma l l o y s i n s i l -i c a t ea n d p h y t i ca c i de l e c t r o l y t e s [J ].C u r r e n t A p pl i e d P h ys i c s ,2010,10(1):255-259.[11] M aY ,L i uN ,W a n g Y ,e t a l .Ef f e c t o f c h r o m a t ea d d i t i v e o nc o r r o s i o nr e s i s t a n c eo fMA Oc o a t i ng so n m a gn e s i u m a l l o ys [J ].J o u r n a l o f t h eC h i n e s eC e r a m i cS o c i e t y ,2011,39(9):1493-1497.[12] S o l d a t o v a E ,B o l b a s o vE ,K o z e l s k a y aA I ,e t a l .T h e e l a s t i c i t yo f c a l c i u m p h o s p h a t eM A Oc o a t i n g s c o n t a i n i n g di f f e r e n t c o n c e n -t r a t i o n s o f c h i t o s a n [J ].I O PC o n f e r e n c eS e r i e s M a t e r i a l sS c i -e n c e a n dE n g i n e e r i n g,2009,544:63-70.[13] G u oP Y ,W a n g N ,Q i nZS ,e ta l .E f f e c to fe l e c t r o l yt e c o m p o s i t i o no n g r o w t h m e c h a n i s m a n ds t r u c t u r eo fc e -r a m i cc o a t i n g so n p u r eT i b yp l a s m ae l e c t r o l yt i co x i d a -t i o n [J ].T r a n s a c t i o n sof M a t e r i a l s &H e a tT r e a t m e n t ,2013,34(7):181-186.[14] S a n k a r aN a r a y a n a nTSN ,P a r k I S ,L e eM H.S t r a t e gi e s t o i m p r o v e t h e c o r r o s i o n r e s i s t a n c e o fm i c r o a r c o x i d a t i o n (MA O )c o a t e d m a g n e s i u m a l l o y sf o rd e gr a d a b l ei m -p l a n t s :P r o s p e c t s a n d c h a l l e n g e s [J ].P r o gr e s s i n M a t e r i -a l sS c i e n c e ,2014,60:1-71.[15] W a n g C ,C h e nJ ,H e JH ,e t a l .E f f e c t o f e l e c t r o l yt e c o n -c e n t r a t i o no n t h e t r i b o l o g i c a l pe rf o r m a n c e o fMA Oc o a t -i ng s o na l u m i n u ma l l o y s [J ].F r o n t i e r so fCh e mi c a lS c i -e n c e a n dE n g i n e e r i n g,2020,12:1-7.[16] L i uS ,G uL ,Z h a oHC ,e t a l .C o r r o s i o n r e s i s t a n c e o f g r a ph e n e -r e i n f o r c e dw a t e r b o r n e e p o x y c o a t i n gs [J ].J o u r n a l o fM a t e r i a l s S c i e n c e&T e c h n o l o g y ,2016,32(05):425-431.[17] Z h a n g XR ,MaR N ,D u A ,e t a l .C o r r o s i o n r e s i s t a n c e o f o r g a n i c c o a t i n g b a s e do n p o l y h e d r a l o l i g o m e r i c s i l s e s qu i -o x a n e -f u n c t i o n a l i z e d g r a p h e n eo x i d e [J ].A p pl i e dS u r f a c e S c i e n c e ,2019,484:814-824.[18] D e ya b M A ,K e e r a ST.E f f e c t o f n a n o -T i O 2p a r t i c l e s s i z e o n t h e c o r r o s i o n r e s i s t a n c e o f a l k y d c o a t i n g[J ].M a t e r i a l s C h e m i s t r y &P h ys i c s ,2014,146(3):406-411.[19] A oN ,L i uD X ,W a n g SX ,e t a l .M i c r o s t r u c t u r ea n dt r i -b o l o g i c a lb e h a v i o ro fa T i O 2/h B N c o m p o s i t ec e r a m i c c o a t i n g fo r m e dv i am i c r o -a r co x i d a t i o no fT i -6A l -4Va l -l o y [J ].J o u r n a lo f M a t e r i a l s S c i e n c e &T e c h n o l o g y,2016,32(10):1071-1076.[20] M o m e n z a d e h M ,S a n j a b i S .T h e e f f e c t o fT i O 2n a n o pa r t i -c l e c o d e po s i t i o no n m i c r o s t r u c t u r ea n dc o r r o s i o nr e s i s t -a n c e o fe l e c t r o l e s s N i Pc o a t i n g [J ].M a t e r i a l s &C o r r o -s i o n ,2012,63(7):614-619.P r e pa r a t i o na n d c o r r o s i o n r e s i s t a n c e o fm i c r o -a r c o x i d e c e r a m i c c o a t i n g o nm a g n e s i u ma l l o y su r f a c e Y U H a o x u n ,MA T i n gx i a (S c h o o l o fM e c h a n i c a l E n g i n e e r i n g ,S o u t h w e s tP e t r o l e u m U n i v e r s i t y ,C h e n g d u610500,C h i n a )A b s t r a c t :MA O -G R /T i O 2co a t i n g w a s p r e p a r e d o n t h e s u r f a c e o fm a g n e s i u ma l l o y b y a d d i n g p o t a s s i u mf l u o r i d e t i t a n a t e a n dG R /T i O 2po w d e r i n t o t h e e l e c t r o l y t e o fm i c r o -a r c o x i d a t i o n r e a c t i o nb y m i c r o -a r c o x i d a t i o nm e t h o d .T h e s u r f a c em o r p h o l o g y a n d s t r u c t u r eo fG R /T i O 2po w d e rw e r e s t u d i e db y S E M a n dF T -I R.S E M ,X R Da n d e l e m e n t a l l i n e s c a n n i n g w e r eu s e d t o s t u d y t h e s u r f a c em o r p h o l o g y ,ph a s e s t r u c t u r e a n d e l e m e n t d i s t r i b u t i o no f MA O -G R /T i O 2c o a t i n g ,a n d t h e c o r r o s i o n r e s i s t a n c e o fMA O -G R /T i O 2co a t i n g w a s s t u d i e db y t h r e e -e l e c t r o d e t e c h n o l o g y .T h e r e s u l t s s h o w e d t h a tn a n oT i O 2co u l db e g r a f t e do n t o t h es u r f a c eo fG O b y s o l -g e lm e t h o dt o g e n e r a t eG R /T i O 2p o w d e r .MA O -G R /T i O 2c o a t i n g w a s m a i n l y c o m p o s e do f M g 2T i O 4p h a s e ,M g 3(P O 4)2p h a s e ,M g a n d M g O p h a s e .T a k i n g t h e i n t e r f a c ea s t h eb o u n d a r y ,T i ,Pa n d Oe l e m e n t so nt h ec o a t i n g si d e w e r eh i g h e r t h a n t h o s e o n t h e s u b s t r a t e s i d e ,a n dM g e l e m e n t s o n t h e s u b s t r a t e s i d ew e r e h i gh e r t h a n t h o s e o n t h e c o a t i n g s i d e .T h e c o r r o s i o n p o t e n t i a l o fMA O -G R /T i O 2co a t i n g w a s -0.723Va n d t h e c o r r o s i o n c u r r e n t d e n -s i t y w a s 8.96ˑ10-8A /c m 2.C o m p a r e dw i t hm a g n e s i u ma l l o y s u b s t r a t e a n dMA Oc o a t i n g ,t h e c o r r o s i o n p o t e n -t i a l o fMA O -G R /T i O 2c o a t i n g w a s i n c r e a s e db y 48.3%a n d 36.7%,w h i c h i n d i c a t e d t h a tMA O -G R /T i O 2co a t -i n g c o u l d s i g n i f i c a n t l y i m p r o v e t h e c o r r o s i o n r e s i s t a n c e o fm a g n e s i u ma l l o y su b s t r a t e .K e y w o r d s :m a g n e s i u ma l l o y ;m i c r o -a r c o x i d a t i o n ;c o m p o s i t e c o a t i n g;c o r r o s i o n r e s i s t a n c e 52010余灏勋等:镁合金表面微弧氧化陶瓷涂层的制备及耐蚀性能。
热处理-有机覆膜预处理镁合金表面的快速仿生矿化研究[摘要]本文研究了热处理-有机覆膜处理对镁合金在不同模拟体液中仿生矿化过程的影响。
实验首先比较了未处理、热处理-有机覆膜预处理后的镁合金az91d试样在模拟体液（simulated body fluid，sbf）中的腐蚀速率和对溶液ph的影响。
然后提高sbf中的某些离子浓度，研究未处理和预处理试样在改性模拟体液（modified sbf， m-sbf）中的仿生矿化行为。
研究结果表明，经过热处理-有机覆膜预处理的az91d试样在sbf溶液中的耐蚀性有较大的提高，有机覆膜的离子诱导作用以及m-sbf溶液中充足的离子供给使羟基磷灰石涂层在试样表面快速、均匀生长。
[关键词]镁合金预处理腐蚀仿生矿化羟基磷灰石中图分类号：tg178文献标识码：a文章编号：1009-914x（2013）17-0097-03镁合金作为一种潜在的人体植入材料，具有优越的生物相容性和力学相容性[1-2]。
它有较好的抗凝血和血液相容性，能促进骨细胞的生成和加速骨折的愈合，不必担心微量金属离子对细胞的毒性[3]。
镁合金的密度（～1.80 g/cm3）与人体密质骨的密度（～1.75 g/cm3）相近；强度和弹性模量等综合力学性能也与人体骨相近，能够有效避免应力阻挡效应[4，5]。
从上世纪就有科学家曾尝试将纯镁用于整形与外伤的手术中[6，7]。
然而，镁合金在人体环境中腐蚀速率过快，所产生的大量气体容易引起皮下鼓泡，导致手术失败[8]。
因此，镁合金在人体中的耐腐蚀研究显得异常关键。
要解决医用镁合金的耐腐蚀性问题，就需要研究镁合金表面改性的方法。
但是，目前关于生物医用镁合金表面改性的报道较少，大部分研究集中于医用纯镁的研究[9]。
目前，医用纯镁表面改性方法主要包括仿生矿化法、激光熔覆、等离子喷涂、电泳沉积等。
与其他表面改性技术相比，仿生矿化法具有所需设备简单、操作方便、沉积工艺易控制等特点[9，10]。
人工骨桥蛋白合成过程## Artificial Bone Bridge Protein Synthesis 英文回答，##。
Introduction:Artificial bone bridge proteins are synthetic materials designed to promote bone regeneration and repair. They mimic the natural structure and properties of bone tissue, providing a scaffold for new bone cells to grow and attach to. The synthesis of artificial bone bridge proteins involves several key steps, including:1. Design and Synthesis of Peptide Sequences:The first step is to design the peptide sequences that will form the backbone of the artificial bone bridge protein. These sequences are typically based on the amino acid composition of natural bone proteins, such as collagen and hydroxyapatite. Peptides are synthesized using solid-phase peptide synthesis or recombinant DNA technology.2. Assembly and Cross-linking:The synthesized peptides are then assembled into athree-dimensional scaffold using cross-linking agents. The cross-linking process creates a stable structure that provides mechanical support and facilitates cell attachment. Various cross-linking techniques can be employed, such as chemical cross-linking, enzymatic cross-linking, or photo-cross-linking.3. Biomineralization:The assembled scaffold is subjected to a biomineralization process to induce the deposition of hydroxyapatite crystals, the primary mineral component of bone. Biomineralization can be achieved through immersionin simulated body fluid, which provides the necessary ions for crystal growth. The resulting structure mimics the mineralized matrix of natural bone tissue.4. Cell Seeding and Culture:Once the artificial bone bridge protein is biomineralized, it is seeded with osteogenic cells, such as mesenchymal stem cells or bone marrow stromal cells. These cells differentiate into osteoblasts, which produce new bone tissue. The cells are cultured in a bioreactor or on a cell culture substrate to promote cell growth and differentiation.5. Implantation and Bone Regeneration:The cell-seeded artificial bone bridge is then implanted into the defect site, where it serves as a scaffold for bone regeneration. The scaffold provides a favorable environment for cell attachment, proliferation, and differentiation, leading to the formation of new bone tissue. Over time, the artificial bone bridge is gradually replaced by newly formed bone, restoring the structural integrity and function of the bone defect.## 中文回答，##。
碳纤维增强磷酸钙骨水泥张睿;张彭风;薛润苗;王志强【摘要】以碳纤维为增强相,Na2HPO4/柠檬酸为调和液,α-磷酸三钙、磷酸四钙、磷酸二氢钙、羟基磷灰石和碳酸钙为原料制备骨水泥,研究不同掺杂比例的短碳纤维对其性能的影响.在磷酸钙骨水泥中掺杂碳纤维能够提高样品的致密性,缩短固化时间,提高抗压强度.当掺杂质量分数0.5％的碳纤维时,骨水泥的初凝、终凝时间分别为9.3和24.9 min,模拟体液中浸泡28 d后抗压强度最大为38.24MPa.掺杂的碳纤维对浸泡液pH影响不大,pH在小范围内浮动,均在人体安全范围内.%The effect of carbon fiber on the performance of calcium phosphate bone cement was studied. Calcium phosphate bone cement doped with carbon fiber was prepared from crtricalcium phosphate, tetracalcium phosphate, monocalcium phosphate monohydrate, hydroxyapatite and calcium carbonate, in which Na2 HPO4/citric acid was added as mixing liquid. The results show that carbon fiber doped in calcium phosphate cement can increase the density, reduce the setting time and enhance the compressive strength. When the doping amount of carbon fiber is 0.5%, the initial setting time and the final setting time is respectively 9. 3 and 24. 9 min. The compressive strength reaches up to 38. 24 MPa after immersed 28 d in the simulated body fluid. Meanwhile, the doping of carbon fiber has little influence on the change of pH, which is in the range of human security.【期刊名称】《大连工业大学学报》【年(卷),期】2012(031)006【总页数】4页(P465-468)【关键词】磷酸钙骨水泥;碳纤维;模拟体液【作者】张睿;张彭风;薛润苗;王志强【作者单位】大连工业大学纺织与材料工程学院,辽宁大连 116034;大连工业大学纺织与材料工程学院,辽宁大连 116034;大连工业大学纺织与材料工程学院,辽宁大连 116034;大连工业大学纺织与材料工程学院,辽宁大连 116034【正文语种】中文【中图分类】R318.080 引言磷酸钙骨水泥的化学成分与人体硬组织相似,能够自行固化,具有良好的可塑性、生物相容性、生物活性、可降解性、骨传导性[1]等优点,因此作为骨修复置换材料被广泛应用于临床医学[2]。
多孔金属植入材料在骨科的应用杨军;杨群【摘要】因外伤、肿瘤、感染等原因造成的骨缺损是骨科临床常见疾患,目前解决这一问题的主要方法为自体骨移植或同种异体骨移植.自体骨移植主要存在取骨量有限,造成附加损伤,感染,出血等缺陷.同种异体骨存在价格昂贵,免疫排斥反应等问题.此外,多种骨材料替代物也越来越多地应用于研究和临床,比如羟基磷灰石,生物陶瓷等.近年来,多孔金属材料由于其良好的生物相容性,较好的抗压强度和与骨接近的弹性模量等优点逐渐成为研究热点.本文针对多孔镁、多孔铁、多孔镍、多孔钽、多孔钛等不同材质的多孔金属材料,对其构建方法、理化特性、基础研究、临床应用等方面进行综述.%Bone defect caused by trauma, tumor and infection is a common disease in orthopedics.Autogenous and allograft bone graft is mainly limited by the amount of graft bone, additional damage, infection, bleeding, immune rejection, etc.A variety of bone substitutes have also been increasingly used in clinical research, such as hydroxyapatite and bioceramics.In recent years, porous metal materials have gradually become the focus of research because of their good biocompatibility, good compressive strength and similar elastic modulus with bone.In this paper, we reviewed the construction methods, physicochemical properties, basic research and clinical application of porous metal materials such as porous magnesium, porous iron, porous nickel, porous tantalum and porous titanium.【期刊名称】《大连医科大学学报》【年(卷),期】2017(039)004【总页数】6页(P397-402)【关键词】骨缺损;植入材料;多孔金属【作者】杨军;杨群【作者单位】大连医科大学附属第一医院脊柱外科,辽宁大连 116011;大连医科大学附属第一医院脊柱外科,辽宁大连 116011【正文语种】中文【中图分类】R687.3+2多孔金属材料是近年来骨科植入材料领域的研究热点之一，虽然其材质多种多样，但它们都有着同样的开放多孔结构，这就可以使新生骨长入其中，从而维持内植物的稳定性。
电流密度对水热电化学沉积HA涂层性能的影响王朴;杜继涛【摘要】在含0. 15mol/L HF,2mol/L H3PO4的水溶液中对Ti6Al4V基体进行阳极氧化处理,然后在0. 02mol/L CaCl2,0. 012mol/L K2HPO4 · 3H2O, 0.139mol/L NaCl的电解液中采用水热电化学沉积方法在预处理的Ti6Al4V基体表面制备羟基磷灰石 (HA)涂层.采用X射线衍射仪 (XRD)、扫描电子显微镜 (SEM)、能谱仪 (EDS)、台阶仪和万能材料试验机等研究沉积过程中电流密度大小对HA涂层物相、微观形貌、厚度、生物活性及结合强度的影响.结果表明:采用水热电化学沉积方法在不同电流密度下均制备出了 HA涂层,涂层表现为分层生长,部分晶体呈花簇状.HA的厚度随电流密度的增加先增大后减小,在1. 25mA/cm2时达到最大为26. 4μm,此时涂层最为致密,与基体的结合强度最高,约为20. 0MPa.模拟体液(SBF)浸泡实验能较快诱导类骨磷灰石 (CHA)的生成,最大直径达到7~8μm,表明涂层具有较好的生物活性.%Ti6Al4V substrates were anodized in aqueous solution containing 0. 15mol/L HF + 2mol/L H3PO4. After that, hydroxyapatite coatings is deposited on the anodized Ti6Al4V substrates surface by hydrothermal-electrochemical method at a constant current in an electro lyte containing 0. 02mol/L CaCl2, 0. 012mol/L K2HPO4 · 3H2O and 0. 139mol/L NaCl. The influence of current density on the coating compositions, microstructure, thickness, bioactivity and bonding strength between the coating and substrate was investigated by XRD, SEM, EDS, step profiler and universal testing machine during deposition process. The results indicate that HA coatings can be successfully obtained on anodized Ti6Al4V surface by hydrothermal-electrochemical deposition with differentcurrent densities. The coatings appear a layered growth and parts of crystals are characterized by flower-shape. The thickness of the HA coatings increases firstly and then decreases with increasing current density. When the current density is 1. 25mA/cm2, the thickness of the HA coatings reaches the maximum 26. 4μm, the coating is the most dense and the bonding strength is near 20. OMPa. The simulated body fluid (SBF) immersion test can quickly promote the deposition of calcium phosphate with a maximum diameter of 7-8μm.【期刊名称】《材料工程》【年(卷),期】2018(046)004【总页数】8页(P58-65)【关键词】Ti6Al4V;阳极氧化处理;水热电化学沉积;羟基磷灰石涂层;结合强度【作者】王朴;杜继涛【作者单位】上海工程技术大学高职学院, 上海 200437;上海市高级技工学校, 上海 200437;上海工程技术大学高职学院, 上海 200437;上海市高级技工学校, 上海200437【正文语种】中文【中图分类】TG174.4钛及钛合金由于具有较好的生物相容性和力学适应性成为人工骨植入体最为理想的生物医用金属材料[1]，但钛合金表面活性不足，其与骨之间只是一种机械嵌连式的骨整合，亟需通过表面改性使之具备诱导骨组织长入并与植入部位实现骨性结合的能力。
*Corresponding author.Tel.:#34-93-402-1134;fax:#34-93-402-1138.E-mail address:lcleries @fao.ub.es (L.Cleries).Biomaterials 21(2000)1861}1865Behavior in simulated body #uid of calcium phosphate coatingsobtained by laser ablationL.Cle ries *,J.M.Ferna ndez-Pradas,J.L.MorenzaDepartament de F n &sica Aplicada i O "ptica,Uni v ersitat de Barcelona,A v da.Diagonal 647,E-08028Barcelona,SpainReceived 28July 1999;accepted 20February 2000AbstractThree types of calcium phosphate coatings onto titanium alloy substrates,deposited by the laser ablation technique,were immersedin a simulated body #uid in order to determine their behavior in conditions similar to the human blood plasma.Neither the hydroxyapatite coating nor the amorphous calcium phosphate coating do dissolve and the -tricalcium phosphate phase of the coating of -tricalcium phosphate with minor phase slightly dissolves.Precipitation of an apatitic phase is favored onto the hydroxyapatite coating and onto the coating of -tricalcium phosphate with minor phase.Onto the titanium alloy substrate reference there is also precipitation but at larger induction times.However,onto the amorphous calcium phosphate coating no precipitate is formed. 2000Elsevier Science Ltd.All rights reserved.Keywords:Calcium phosphate;HA;Pulsed laser deposition;SBF1.IntroductionLaser ablation is a technique employed for the depo-sition of calcium phosphate coatings onto metallic substrates that will be used as implants for bone recon-struction.With this technique,calcium phosphate coatings with tailored phases and structures have suc-cessfully been produced [1,2]and their dissolution properties in undersaturated conditions have been assessed [3,4].However,the real body #uid conditions are saturated with respect to the hydroxyapatite phase,that is,the concentration of calcium ions is higher than the one in equilibrium with this phase.Consequently,it is interest-ing to also test the calcium phosphate coatings in condi-tions closer to the in vivo situation,in order to know their integrity in these conditions and the catalytic }react-ive properties of their surfaces towards precipitation pro-cesses.Therefore,amorphous calcium phosphate coatings (ACP),hydroxyapatite coatings (HA),and coatings of -tricalcium phosphate with minor phase ( -TCP)deposited by laser ablation were immersed in a saturatedsolution for di !erent time periods and the evolution oftheir constitutive properties was determined.The saturated solution used was the simulated body #uid (SBF),a solution whose ion concentrations and pH are almost equal to those of human blood plasma [5].This solution is also the one utilized in the biomimetic (pre-cipitation)process for the production of apatite layers onto the sol }gel activated titanium substrates [6].2.ExperimentalThe simulated body #uid [5]was prepared by dissolv-ing reagent grade chemicals strictly in the following or-der:NaCl,NaHCO ,KCl,K HPO )3H O,MgCl)6H O,CaCl )2H O,and Na SOinto deionized water.The #uid was bu !ered at pH "7.4at 373C with tris-hydroxymethyl-aminomethane and hydrochloric acid.The inorganic composition of SBF emulates that of human blood plasma,as shown in Table 1.No precipita-tion was observed during #uid preparation.Coatings of HA, -TCP,and ACP deposited onto titanium alloy (Ti }6Al }4V)substrates by laser ablation of HA with an excimer laser at 248nm and bare titanium alloy substrates degreased in ultrasonic baths with triclorethylene,acetone and ethanol,were used.Details on the preparation and characterization of the coatings0142-9612/00/$-see front matter 2000Elsevier Science Ltd.All rights reserved.PII:S 0142-9612(00)00060-0Table 1Milimolar concentrations (m M )of the ions of the SBF solution and comparison to those of human plasma [5]Na >K >Ca >Mg >Cl \HCO \HPO \SO \ SBF142.0 5.0 2.5 1.5147.8 4.2 1.00.5Human plasma142.05.02.51.5103.027.01.00.5Bu !er (TRIS solution):tris-hydroxymethyl-aminomethane (CH OH) CNH50m M #HCl 45m M.Fig.1.Scanning electron micrographs for (a)the HA coating,(b)the -TCP coating,(c)the ACP coating,after 8days immersion,and (d)the titaniumalloy substrate after 28days immersion.selected for this study,can be found in previous papers [1}4].All the coatings had a thickness around 1 m.Each sample,with an area of 1cm ,was soaked in 24ml of the SBF solution into separate stopped vials at 373C in a thermostatic oven,for di !erent periods:1,4,8,and 28days.At that point,each representative sample was care-fully washed with distilled water,air dried,weighted and characterized by X-ray di !raction,Raman spectroscopy and scanning electron microscopy (SEM).3.Results 3.1.HA coatingThe SEM micrograph after 8days immersion,depicted in Fig.1a,shows that over the columnar coating struc-ture,a quite dense precipitated layer appears.This layer is not strongly adhered to the underlying HA coating since it cleanly detaches from the HA coating in certain1862L.Cle %ries et al./Biomaterials 21(2000)1861}1865Fig.2.X-ray di !raction spectra for (a)the HA coating,(b)the -TCP coating,(c)the ACP coating,before and after 8days immersion,and (d)the titanium alloy substrate before and after 28days immersion.areas,underexposing the original HA surface which doesnot seem to have degraded.The X-ray di !raction spectra before and after 8days in SBF are shown in Fig.2a.The initial spectrum contains,apart from the substrate peaks,only HA peaks that do not diminish after 8days in solution.It is distinguishable at day 8that the apparition of a broad band centered around 323superimposed to the HA peaks,with an additional peak at 25.93,which are attributed to a non-well crystallized apatite [7]with a preferred (002)orientation.A representative Raman spectrum after 8days (Fig.3a)shows the 962cm \ peak of the HA coating and a relatively small,almost indis-tinct,shoulder towards lower wavenumbers that is also attributable to a non-well crystallized apatite structure [8].The gains in mass of the coating-substrate system,tabulated in Table 2,indicate the growth of the precipi-tate with time.3.2. -TCP coatingThe SEM micrograph in Fig.1b shows that there is the formation of a thick precipitate at day 8.There are some parts where this precipitate has detached,underexposing the coating surface,which does not seem to be thatdegraded.The X-ray di !raction peaks attributed to the minor -TCP slightly diminish after immersion and those of -TCP do not change (Fig.2b).Additionally,the broad band centered around 32and the 25.93peak,attributed to a non-well crystallized apatite structure with a preferred (002)orientation,appear.The represen-tative "nal Raman spectrum (Fig.3b)shows a broad band that contains the TCP peaks at 947and 972cm \ ,but the existence of an intermediate peak at around 960cm \ suggests also the presence of a non-well crystallized apatite structure.The mass changes for the 4and 8day period,which are also tabulated in Table 2,are similar,indicating the early saturation of the precipi-tation process.3.3.ACP coatingIn the SEM image (Fig.1c)no substantial change is detected,neither dissolution nor precipitation,since the original morphology with droplets is maintained.The ACP coating does not show any X-ray di !raction peak other than the substrate ones after 8days immersion (Fig.2c).The representative "nal Raman spectrum (Fig.3c)has only a broad band which is centered towardsL.Cle %ries et al./Biomaterials 21(2000)1861}18651863Fig.3.Raman spectra for(a)the HA coating,(b)the -TCP coating, (c)the ACP coating,after8days immersion,and(d)the titanium alloy substrate after28days immersion.Table2Mass variations in mg/cm and changes observed with the character-ization techniques1day4days8days28days SEM XRDHA0.41Ppte No1.11Ppte NCA-TCP 1.17Ppte NCA#1.19Ppte NCA# ACP!0.03No No!0.03No No!0.01No No Titanium0.23Ppte*alloy0.85Ppte NCANo:non-detected change;NCA:non-well crystallized apatite struc-ture; :decrease in -TCP content;Ppte:precipitate observed.950cm\ ,characteristic of an amorphous structure[6]. Table2con"rms that there is no uptake or loss of mass.3.4.Bare titanium alloy substrateThe SEM image shows the precipitate found after28 days(Fig.1d).The X-ray di!raction spectrum(Fig.2d) indicates that it has also a non well crystallized apatite structure with a(002)preferred orientation.A broad band centered towards960cm\ in its representative "nal Raman spectrum(Fig.3d)also suggests that the precipitate has a non well crystallized apatite structure. Table2shows the mass uptake for this sample.4.DiscussionIn a previous study[3]the same type of calciumphosphate coatings used in the present work were testedin Ca-free undersaturated conditions,and it was foundthat the HA coatings were stable,that the -TCP phasein the -TCP coatings completely dissolved leavinga microporous coating and that the ACP coatings com-pletely dissolved.In the saturated conditions of the SBF neither the HA orthe -TCP phase of the -TCP coatings do dissolve andon both coatings a precipitate is found.The fact that thesephases do not dissolve is not an unexpected result if we takeinto account that this solution is saturated for the di!erentcalcium phosphates,with di!erent degrees of supersatura-tion represented by di!erent negative Gibbs free energies(for instance,!7.94kJ/mol for HA and!3.72kJ/mol for -TCP[9]).The precipitate that is formed has a non-well crystallized apatite structure with a(002)preferred orienta-tion.Indeed,apatite is the most thermodinamically favoredphase to precipitate(has the highest negative Gibbs freeenergy value),and the preferred(002)orientation isa common"nding among other studies[10,11].We have found that the precipitation rate is in theorder -TCP'HA'Ti'ACP.The precipitate isthen formed faster onto the -TCP coating than ontothe HA coating.Radin et al.[12]reported that in a SBFsolution the -TCP phase dissolved during an inductiontime before precipitation took place and suggested that itwas this initial phase dissolution leading to supersatura-tion that consequently helped precipitation.Weng et al.[13]have also suggested that the HA crystalline struc-ture is not critical in the nucleation process.Followingthese interpretations,the dissolution of the -TCP phaseof the -TCP coating could favor the precipitation ofthe non-well crystallized apatite phase on this coatingwhile for the HA coating the absence of dissolutionwould delay this precipitation.Onto the bare titanium alloy the precipitation of thenon-well crystallized apatite phase is observed althoughthe induction time towards precipitation is larger thanfor the HA coating,and is similar to those reported in theliterature[14].Ducheyne et al.[15]have also reportedthat precipitation in a SBF solution occurs earlier ontoHA than onto titanium disks.Taking into account thatneither the HA coating not the titanium alloy do releaseinto the solution the calcium or phosphate ions[3,4]thatcould help precipitation,this would suggest that in thiscase the crystalline structure is indeed important in dic-tating the di!erences in the rate of nucleation.Remarkably,there is no dissolution of the ACP coat-ing nor precipitation processes onto its surface.Contra-dictory reports have been found regarding the behaviorin a SBF solution of ACP coatings obtained by RFmagnetron sputtering:Wolke et al.[16]reported thatthese ACP coatings during immersion were maintained1864L.Cle%ries et al./Biomaterials21(2000)1861}1865and in some areas a calcium phosphate precipitate was found.However,Yoshinari et al.[17]observed dissolu-tion of ACP coated disks within one day without precipi-tation of a calcium phosphate phase.They attributed this di!erence in precipitation processes to the variations on the ratio of solution volume to sample area,the Ca/P ratio,the grain size of the coating,and the impurities.The absence of dissolution for our ACP coating could be explained on the basis that the SBF solution could be saturated with respect to this particular ACP phase.This degree of saturation cannot be easily calculated for amorphous calcium phosphate phases since it largely depends on their Ca/P ratio which can#uctuate.There is no precipitation onto the ACP coating even when onto the titanium alloy substrate a precipitate is found.This is quite surprising since,in the absence of dissolution,the ACP coating should provide a better substrate for the nucleation of apatite compared to the titanium alloy substrate since it already has calcium and phosphate ions in its structure.Therefore,other factors intervening in the mechanisms of the formation of this precipitate,apart from the existence of a calcium phosphate surface or calcium and phosphate release,should be considered.5.ConclusionThe HA coating deposited by excimer laser ablation con"rms its stability in saturated conditions towards dissolution.The ACP coating and the -TCP phase of the -TCP coating are also stable under these condi-tions.The HA and -TCP coatings favor earlier the precipitation of an apatitic phase with a(002)preferred orientation.Onto the titanium alloy substrate reference there is also precipitation but at larger induction times. However,onto the amorphous calcium phosphate coat-ing no precipitate is formed.AcknowledgementsThis work is part of a research program"nanced by DGESIC of the Spanish Government(Project MAT98-0334-C02-01)and DGR of the Catalan Government. References[1]Ferna ndez-Pradas JM,Cle ries L,Sardin G,Morenza JL.Depos-ition of hydroxyapatite thin"lms by excimer laser ablation.Thin Solid Films1998;317:393}6.[2]Ferna ndez-Pradas JM,Cle ries L,Sardin G,Morenza JL,Hydroxyapatite coatings grown by pulsed laser deposition with a beam of355nm wavelength.J Mater Res1999;14: 4715}9.[3]Cle ries L,Ferna ndez-Pradas JM,Sardin G,Morenza JL.Dissolu-tion behaviour of calcium phosphate coatings obtained by laser ablation.Biomaterials1998;19:1483}7.[4]Cle ries L,Ferna ndez-Pradas JM,Sardin G,Morenza JL.Ap-plication of dissolution experiments to characterise the structure of pulsed laser-deposited calcium phosphate coatings.Bio-materials1999;20:1401}5.[5]Kokubo T,Kushitani H,Sakka S,Kitsugi T,Yamamuro T.Solutions able to reproduce in vivo surface changes in bioactive glass-ceramic A-W .Biomed Mater Res1990;24:721}4.[6]Tanahashi M,Kokubo T,Nakamura T,Katsura Y,Nagano M.Ultrastructural study of an apatite layer formed by a biomimetic process and its bonding to bone.Biomaterials1996;17: 47}51.[7]Tong W,Wang Z,Zhang X,Yang A,Feng J,Cao Y,et al.Studieson the di!usion maximum in X-ray di!raction patterns of plasma-sprayed hydroxyapatite coatings.J Biomed Mater Res 1998;40:407}13.[8]Weinlaender M,Beumer III J,Kenney EB,Moy PK,Adar F.Raman microprobe investigation of the calcium phosphate phases of three commercially available plasma-#ame-sprayed hy-droxyapatite-coated dental implants1.J Mater Sci:Mater Med 1992;3:397}401.[9]Ishikawa K,Takagi S,Chow LC,Ishikawa Y,Eanes ED,AsaokaK.Behavior of a calcium phosphate cement in simulated blood plasma in vitro.Dent Mater1994;10:26}32.[10]Ban S,Maruno S,Iwata H,Itoh H.Calcium phosphate precipita-tion on the surface of HA-G-Ti composite under physiologic conditions.J Biomed Mater Res1994;28:65}71.[11]Wen HB,Wolke JGC,de Wijn JR,Liu Q,Cui FZ,de Groot K.Fast precipitation of calcium phosphate layers on titanium induced by simple chemical treatments.Biomaterials1997;18:1471}8. [12]Radin SR,Ducheyne P.The e!ect of calcium phosphate ceramiccomposition and structure on in vitro behavior.II.Precipitation.J Biomed Mater Res1993;27:35}45.[13]Weng J,Liu Q,Wolke JGC,Zhang X,de Groot K.Formationand characteristics of the apatite layer on plasma-sprayed hy-droxyapatite coatings in simulated body-#uid.Biomaterials 1997;18:1027}35.[14]Kim HM,Miyaji F,Kokubo T,Nakamura T.Preparation ofbioactive Ti and its alloy via simple chemical surface treatment.J Biomed Mater Res1996;32:409}17.[15]Ducheyne P,Radin R,Ishikawa K.The rate of calcium phosphateprecipitation on metal and ceramics,and the relationship to bioactivity.In:Ducheyne P,Kokubo T,van Blitterswijk CA, editors.Bone-bonding biomaterials.Leiderdorp:Reed Healthcare Communications,1992.p.213}8.[16]Wolke JGC,van der Waerden JPCM,de Groot K,Jansen JA.Stability of radiofrequency magnetron sputtered calcium phos-phate coatings under cyclically loaded conditions.Biomaterials 1997;18:483}8.[17]Yoshinari M,Hayakawa T,Wolke JGC,Nemoto K,Jansen JA.In#uence of rapid heating with infrared radiation on RF magnet-ron-sputtered calcium-phosphate coatings.J Biomed Mater Res 1997;37:60}7.L.Cle%ries et al./Biomaterials21(2000)1861}18651865。
