Synthesis and characterization of lanthanum-incorporated hydroxyapatite coatings

doi:10.3969/j.issn.2095-4344.2014.08.013

Abstract

Abstract:

BACKGROUND: Hydroxyapatite-coated titanium substrates improve the biocompatibility and have the property of intimating ossteointegration with host bonebed. However, hydroxyapatite lacks the necessary mechanical strength and degrades easily in the extracellular fluids, which may affect the stability of the titanium implant.
OBJECTIVE: To study the synthesis and characterization of lanthanum-incorporated hydroxyapatite coatings.
METHODS: Lanthanum-incorporated hydroxyapatite coatings were prepared by hydroxyapatite and 10%, 20% and 30% lanthanum, respectively, by means of sol-gel, which were then deposited on titanium substrates with dip-withdrawal technique. Surface morphology and crystalline microstructure of the coatings were observed by scanning electron microscope. The presence of functional groups for the obtained samples was performed by Fourier transform infrared absorption spectroscopy and X-ray diffraction. The Ca2+ concentration released from the coatings was measured by atomic absorption spectrometry for analysis of degradation property.
RESULTS AND CONCLUSION: With the increase of lanthanum content, the diffraction peak and crystallinity of lanthanum-incorporated hydroxyapatite coatings were increased, but the whole structure of lanthanum-incorporated hydroxyapatites had little changes. The crystal structure maintained stable with charge balance. The lanthanum-incorporated hydroxyapatite coatings showed uniform and high-dense structure and were free of cracks, indicating the coatings had good bonding strength. Under the simulated biological environment, based on the determination of Ca2+ release from the coatings, we can conclude the lanthanum-incorporated hydroxyapatite coatings have a stronger acidoresistance.

中国组织工程研究杂志出版内容重点：生物材料；骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性；组织工程

全文链接：

Key words: biocompatible materials, hydroxyapatites, titanium, lanthanum

CLC Number:

R318

Lou Wei-wei, Dong Yi-wen, Jin Yi-fan, Liu Jin-song. Synthesis and characterization of lanthanum-incorporated hydroxyapatite coatings[J]. Chinese Journal of Tissue Engineering Research, 2014, 18(8): 1224-1230.

Figures/Tables 3

2.2 傅里叶红外光谱分析图2B为掺镧羟基磷灰石和纯羟基磷灰石粉末的傅利叶红外分析图谱，从图中可以看出随着掺镧量的递增，曲线相应特征谱带出现向低波数移动的趋势，这是由于La3+离子取代Ca2+，影响了P-O键的键长造成的结果。在波数470，564，603，958，1 043，1 093 cm-1的吸收波峰为PO43-基团的特征谱带，从图中可见上述波数相应的波峰与纯羟基磷灰石各特征波谱带相一致，其中470 cm-1是PO43-的振动吸收谱带，958 cm-1是PO43-的对称伸缩振动吸收峰，1 043 cm-1和1 093 cm-1为PO43-的非对称伸缩振动吸收峰，3 440 cm-1和1 629 cm-1为样品中所含H2O的特征谱带，在875 cm-1处未见HPO42-的特征谱带，说明La3+可以顺利取代Ca2+进入羟基磷灰石的晶体结构中，形成稳定的键合，对羟基磷灰石的整体结构影响较小。在图中可以看到3 440，1 629 cm-1为H2O的特征谱带，然而常规O-H的特征谱带多见于630 cm-1和3 570 cm-1处，其中纯羟基磷灰石吸收光谱中波数3 568 cm -1可见处有一波峰为OH-的伸缩振动吸收峰，但掺镧羟基磷灰石中未见特征谱带代表OH-，这证明了La3+替代了Ca2+，由于La3+比Ca2+多一个正电荷，进入晶格后，部分OH-转化为O-，维持了晶体的结构稳定和电荷平衡[35]。 2.3 扫描电子显微镜分析图3A可以直接观察到掺镧羟基磷灰石涂层重复涂5次后在钛基体表面均匀涂覆，经过 900 ℃退火煅烧之后未见任何裂纹。在高倍镜下可看到涂层中的磷灰石晶体呈棒状，晶粒之间紧密排列未见明显缝隙。图3B断面扫描电镜可以看出掺镧羟基磷灰石涂层致密均匀，厚度约2 μm，和钛基底结合紧密，两者之间虽有可见的界面，但没有明显缝隙和裂纹，提示涂层具有较好的结合强度。同样，作为对照，图3C可见同样方法制备的羟基磷灰石涂层晶粒形貌与掺镧羟基磷灰石相似也呈棒状，由此可推断出羟基磷灰石中掺入其他微量元素之后并不会影响磷灰石的晶粒结构形成，同样图3D可见羟基磷灰石涂层重复涂5次后在钛基体表面均匀附着，结构致密，未出现任何断裂和破坏。"

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