小分子磷酸酯单体诱导仿生矿化的机理研究

In the biomimetic mineralization of collagen, the theory of polymer induced liquid precursor(PILP) is widely accepted, and the macromolecular polymers such as polyacrylic acid (PAA) and polyaspartic acid (PAsp) have been used to induce the mineralization of collagen. However, there is few research on whether small molecular monomer such as phosphate monomer could induce collagen mineralization. Our preliminary research showed that small molecular phosphate monomer: MDP could induce mineralization of reconstituted type I collagen fibrils. But the specific mechanism is not clear. Since MDP can bind to specific stereotactic sites of type I collagen, it is assumed that MDP can regulate the formation of calcium and phosphate minerals and induce collagen biomimetic mineralization. This study will investigate the mechanism of MDP inducing biomimetic mineralization which could provide a new way and method for biomimetic mineralization. Cryo-TEM is used in the dynamic observation study to explore whether MDP could regulate the formation of calcium phosphate minerals in calcium phosphate solution and collagen mineralization; The adsorption/desorption experiment is to elucidate the nature of the interaction between MDP and collagen; and the contact angle between collagen and amorphous calcium phosphate (ACP) is determined.

聚合物诱导的液态前驱体的仿生矿化理论已被广泛接受，其利用大分子聚合物如聚丙烯酸（PAA）、聚天冬氨酸(PAsp)等诱导了胶原的矿化。但是对于小分子单体如磷酸酯单体是否能诱导胶原的矿化研究甚少。我们初步研究发现小分子磷酸酯单体：甲基丙烯酰氧癸基磷酸酯（MDP）具有诱导重组胶原纤维矿化的能力，但其机理不清。由于MDP能与胶原纤维上的特定立体位点结合，假设在此基础上MDP可调控钙磷矿物以及诱导胶原仿生矿化。拟用cryo-TEM等原位追踪研究MDP调控钙磷溶液中矿物质的形成及胶原的矿化；采用吸附/解吸附实验分析MDP与胶原的作用方式；测定胶原与无定形磷酸钙的接触角等方法来探索小分子磷酸酯单体MDP诱导仿生矿化的机制，为胶原的仿生矿化提供一种新的思路和方法。

甲基丙烯酰氧基二氢磷酸酯（MDP）可诱导矿化，但尚未有令人信服的证据表明其能够诱导纤维内矿化。聚合物作为无定形前驱体的稳定剂/诱导剂在仿生矿化中起着关键作用。目前，未添加聚合物的MDP诱导的仿生矿化尚未得到充分验证或阐明。通过将三维随机光学重建显微镜（3D-STORM）、表面zeta电位、接触角测量、电感耦合等离子体光发射光谱（ICP-OES）、透射电子显微镜（TEM）、原子力显微镜（AFM）和傅里叶变换红外光谱（FTIR）与圆二色谱（CD）相结合，我们发现，两亲性MDP不仅可以通过释放质子使牙本质脱矿，还可以渗透包括牙本质胶原在内的胶原纤维，打破多肽之间的氢键，解开三螺旋结构，最终通过形成化学键固定胶原。与化学磷酸化修饰不同，MDP结合的胶原蛋白作为巨大的胶原蛋白磷酸化蛋白（HCPP）发挥作用。HCPP可以在不添加聚合物添加剂的情况下，通过静电吸引交替吸引钙和磷酸盐，从而诱导仿生矿化。因此，我们在此提出了具有脱矿和再矿化能力的两亲性MDP单体的双重功能。游离状态下的MDP可通过释放质子使牙本质基质脱矿，而胶原结合状态下的MDP与HCPP一样可诱导纤维内矿化。具有脱矿和再矿化特性的MDP单体的双重功能可能会在粘接牙科和预防牙科中创造新的时代。