Organic–inorganic composites are novel bone substitutes that can ameliorate the mismatch of Young's moduli between natural bone and implanted ceramics. Phosphate groups contribute to the formation of apatite in a simulated body fluid (SBF) and the adhesion of osteoblast-like cells. Therefore, modification of a polymer with these functional groups is expected to enhance the ability of the organic–inorganic composite to bond with bone. Two phosphate groups have been used, phosphonic acid (–C–PO₃H₂) and phosphoric acid (–O–PO₃H₂). However, the effects of structural differences between these phosphate groups have not been clarified. In this study, the apatite formation of copolymers modified with Ca²⁺ and either –C–PO₃H₂ or –O–PO₃H₂ was examined. The mechanism of apatite formation is discussed based on analytical and computational approaches. The copolymers containing –O–PO₃H₂, but not those containing –C–PO₃H₂, formed apatite in the SBF, although both released similar amounts of Ca²⁺ into the SBF. Adsorption of HPO₄²⁻ from –O–PO₃H₂ in the SBF following Ca²⁺ adsorption was confirmed by zeta-potential measurement and X-ray photoelectron spectroscopy. The measurement of the complex formation constant revealed that the –O–PO₃²⁻⋯Ca²⁺ complex was thermodynamically unstable enough to convert into CaHPO₄, which was not the case with –C–PO₃²⁻⋯Ca²⁺. The formation of CaHPO₄-based clusters was found to be a key factor for apatite nucleation. In conclusion, this study revealed that modification with –O–PO₃H₂ was more effective for enhancing apatite formation compared with –C–PO₃H₂.

中文翻译：

---

磷酸根基团对模拟体液中 Ca ²⁺改性的共聚物中磷灰石形成的结构影响

有机-无机复合材料是新颖的骨骼替代品，可以改善天然骨骼与植入陶瓷之间的杨氏模量不匹配。磷酸盐基团有助于模拟体液（SBF）中磷灰石的形成以及成骨细胞样细胞的粘附。因此，用这些官能团修饰聚合物有望增强有机-无机复合材料与骨骼结合的能力。使用了两个磷酸基团，膦酸（–C–PO ₃ H ₂）和磷酸（–O–PO ₃ H ₂）。然而，这些磷酸盐基团之间的结构差异的影响尚未阐明。在这项研究中，Ca ²⁺改性的共聚物的磷灰石形成并检查了–C–PO ₃ H ₂或–O–PO ₃ H ₂。基于分析和计算方法，讨论了磷灰石形成的机理。含有–O–PO ₃ H ₂的共聚物，但不含–C–PO ₃ H ₂的共聚物，在SBF中形成了磷灰石，尽管两者都向SBF中释放了相似量的Ca ²⁺。Ca ²⁺对SBF中–O–PO ₃ H ₂的HPO ₄ ^2-的吸附通过ζ电势测量和X射线光电子能谱确认了吸附。络合物形成常数的测量结果表明，–O–PO ₃ ²⁻ ⋯Ca ²⁺络合物在热力学上不稳定，足以转化为CaHPO ₄，–C–PO ₃ ²⁻ ⋯Ca ²⁺则不是这种情况。发现基于CaHPO ₄的团簇的形成是磷灰石成核的关键因素。总之，这项研究表明，与–C–PO ₃ H ₂相比，–O–PO ₃ H ₂修饰对增强磷灰石形成更有效。