Nge Thi Thi, Sugiyama Junji
Laboratory of Biomass Morphogenesis and Information, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
J Biomed Mater Res A. 2007 Apr;81(1):124-34. doi: 10.1002/jbm.a.31020.
The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals.
通过在生理条件下（37摄氏度，pH值7.4）将不同的细菌纤维素（BC）标本浸泡在模拟体液（1.5 SBF）中，模拟磷灰石形成的自然过程，研究了生物聚合物细菌纤维素（BC）的磷灰石形成能力。从衰减全反射傅里叶变换红外光谱（ATR-FTIR）和电感耦合等离子体发射光谱（ICP-AES）分析可知，无论底物如何，在BC微纤维表面成核的晶相都是缺钙碳酸磷灰石，这是通过最初形成磷酸八钙（OCP）或类OCP磷酸钙相实现的。扫描电子显微镜（SEM）、场发射扫描电子显微镜（FE-SEM）和透射电子显微镜（TEM）观察到的沉积物形态显示，相对于底物，薄膜板的精细结构结合在一起形成了各种尺寸（从小于1微米到3微米）的磷灰石球。通过2,2,6,6-四甲基哌啶-1-氧基（TEMPO）介导的氧化进行表面改性，该氧化过程可在BC微纤维表面的伯羟基选择性氧化时轻易形成活性羧基官能团，提高了磷灰石成核速率。发现TEMPO介导的氧化后用氯化钙溶液进行离子交换处理与其他BC底物有显著不同，其沉积物重量最高且磷灰石球尺寸最小。BC底物诱导矿化速率的作用因BC底物的性质而异，这强烈影响磷灰石晶体的生长行为。
