Facile Preparative Access to Bioactive Silicon Oxycarbides with Tunable Porosity
Facile Preparative Access to Bioactive Silicon Oxycarbides with Tunable Porosity
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DOI：
10.3390/ma12233862
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发表时间：
2019-11
期刊：
影响因子：
3.4
通讯作者：
Fang Xie;E. Ionescu;M. Arango-Ospina;R. Riedel;A. Boccaccini;I. Gonzalo-Juan
中科院分区：
文献类型：
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作者：
Fang Xie;E. Ionescu;M. Arango-Ospina;R. Riedel;A. Boccaccini;I. Gonzalo-Juan
本工作采用溶胶凝胶法和惰性气氛热处理(热解)法合成了不同钙含量的含钙碳氧化硅(SiCaOC)。结果表明，低Ca负载量(Ca/Si摩尔比=0.05或0.12)的SiCaOC材料为X射线非晶态，其玻璃网络中含有Q3位，表明钙离子存在于非桥氧位。高Ca含量(即Ca/Si摩尔比=0.50)的SiCaOC具有结晶硅酸钙(主要是假硅灰石)的存在。此外，研究还表明，Ca的加入对SiOC玻璃网络的孔隙率和比表面积有显著影响。结果表明，制备的无钙SiOC材料无孔，比表面积为22.5m~2/g，而Ca/Si摩尔比为0.05时的SiCaOC具有中孔结构，其比表面积为123.4 m~2/g。因此，Ca/Si摩尔比为0.12的SiCaOC是大孔的，SSA值为39.5m2/g。模拟体液(SBF)中的生物活性评估证实，与相对惰性的三元碳化硅参照物不同，所有SiCaOC样品在浸泡7天后都形成了羟基磷灰石。特别是，与Ca/Si摩尔比为0.12的SiCaOC相比，Ca/Si摩尔比为0.05的SiCaOC具有更强的磷灰石形成能力；这种差异被认为是由于Ca/Si摩尔比为0.05的样品的SSA显著增加的直接结果。本工作表明，钙离子掺入碳化硅玻璃网络对其生物活性有两种影响：第一，钙离子促进了网络的轻微解聚，明显地触发了羟基磷灰石的形成(比较了SiOC和SiCaOC在SBF暴露下的生物活性行为，其中Ca/Si摩尔比为0.12)；第二，钙离子的掺入似乎强烈地影响了所制备的SiCaOC材料的孔隙率和比表面积。在硅氧碳化硅玻璃网络中存在一个最佳的钙负载量(当Ca/Si摩尔比为0.05时)，它提供了介孔并达到了最大的比表面积，这对材料的生物活性都是非常有利的。钙负载量的增加除了导致硅酸钙的结晶外，还会导致孔的粗化(即大孔率)和比表面积的显著降低，这两个方面都对生物活性产生了负面影响。
In the present work, Ca-containing silicon oxycarbides (SiCaOC) with varying Ca content have been synthesized via sol-gel processing and thermal treatment in inert gas atmosphere (pyrolysis). It has been shown that the as-prepared SiCaOC materials with low Ca loadings (Ca/Si molar ratios = 0.05 or 0.12) were X-ray amorphous; their glassy network contains Q3 sites, indicating the presence of Ca2+ at non-bridging-oxygen sites. SiCaOC with high Ca content (i.e., Ca/Si molar ratio = 0.50) exhibits the presence of crystalline calcium silicate (mainly pseudowollastonite). Furthermore, it has been shown that the incorporation of Ca into the SiOC glassy network has a significant effect on its porosity and specific surface area. Thus, the as-prepared Ca-free SiOC material is shown to be non-porous and having a specific surface area (SSA) of 22.5 m2/g; whereas SiCaOC with Ca/Si molar ratio of 0.05 exhibits mesoporosity and a SSA value of 123.4 m2/g. The further increase of Ca content leads to a decrease of the SSA and the generation of macroporosity in SiCaOC; thus, SiCaOC with Ca/Si molar ratio of 0.12 is macroporous and exhibits a SSA value of 39.5 m2/g. Bioactivity assessment in simulated body fluid (SBF) confirms the hydroxyapatite formation on all SiCaOC samples after seven days soaking, unlike the relatively inert ternary silicon oxycarbide reference. In particular, SiCaOC with a Ca/Si molar ratio of 0.05 shows an increased apatite forming ability compared to that of SiCaOC with Ca/Si molar ratio of 0.12; this difference is considered to be a direct consequence of the significantly higher SSA of the sample with the Ca/Si ratio of 0.05. The present work indicates two effects of Ca incorporation into the silicon oxycarbide glassy network on its bioactivity: Firstly, Ca2+ is shown to contribute to the slight depolymerization of the network, which clearly triggers the hydroxyapatite formation (compare the bioactive behavior of SiOC to that of SiCaOC with Ca/Si molar ratio 0.12 upon SBF exposure); secondly, the Ca2+ incorporation seems to strongly affect the porosity and SSA in the prepared SiCaOC materials. There is an optimum of Ca loading into the silicon oxycarbide glassy network (at a Ca/Si molar ration of 0.05), which provides mesoporosity and reaches maximum SSA, both highly beneficial for the bioactive behavior of the materials. An increase of the Ca loading leads, in addition to the crystallization of calcium silicates, to a coarsening of the pores (i.e., macroporosity) and a significant decrease of the SSA, both negatively affecting the bioactivity.