Li Yuping, Chen Xi, Fok Alex, Rodriguez-Cabello Jose Carlos, Aparicio Conrado
Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota , Minneapolis, Minnesota 55455, United States.
GIR Bioforge, University of Valladolid , Valladolid 47002, Spain.
ACS Appl Mater Interfaces. 2015 Nov 25;7(46):25784-92. doi: 10.1021/acsami.5b07628. Epub 2015 Nov 11.
The use of insoluble organic matrices as a structural template for the bottom-up fabrication of organic-inorganic nanocomposites is a powerful way to build a variety of advanced materials with defined and controlled morphologies and superior mechanical properties. Calcium phosphate mineralization in polymeric hydrogels is receiving significant attention in terms of obtaining biomimetic hierarchical structures with unique mechanical properties and understanding the mechanisms of the biomineralization process. However, integration of organic matrices with hydroxyapatite nanocrystals, different in morphology and composition, has not been well-achieved yet at nanoscale. In this study, we synthesized thermoresponsive hydrogels, composed of elastin-like recombinamers (ELRs), to template mineralization of hydroxyapatite nanocrystals using a biomimetic polymer-induced liquid-precursor (PILP) mineralization process. Different from conventional mineralization where minerals were deposited on the surface of organic matrices, they were infiltrated into the frameworks of ELR matrices, preserving their microporous structure. After 14 days of mineralization, an average of 78 μm mineralization depth was achieved. Mineral density up to 1.9 g/cm(3) was found after 28 days of mineralization, which is comparable to natural bone and dentin. In the dry state, the elastic modulus and hardness of the mineralized hydrogels were 20.3 ± 1.7 and 0.93 ± 0.07 GPa, respectively. After hydration, they were reduced to 4.50 ± 0.55 and 0.10 ± 0.03 GPa, respectively. These values were lower but still on the same order of magnitude as those of natural hard tissues. The results indicated that inorganic-organic hybrid biomaterials with controlled morphologies can be achieved using organic templates of ELRs. Notably, the chemical and physical properties of ELRs can be tuned, which might help elucidate the mechanisms by which living organisms regulate the mineralization process.
使用不溶性有机基质作为自下而上制备有机-无机纳米复合材料的结构模板，是构建具有特定和可控形态以及优异机械性能的各种先进材料的有效方法。就获得具有独特机械性能的仿生分级结构以及理解生物矿化过程的机制而言，聚合物水凝胶中的磷酸钙矿化受到了广泛关注。然而，在纳米尺度上，形态和组成不同的有机基质与羟基磷灰石纳米晶体的整合尚未得到很好的实现。在本研究中，我们合成了由类弹性蛋白重组体（ELR）组成的热响应水凝胶，以使用仿生聚合物诱导液体前驱体（PILP）矿化过程来模板化羟基磷灰石纳米晶体的矿化。与传统矿化中矿物质沉积在有机基质表面不同，它们渗透到ELR基质的框架中，保留了其微孔结构。矿化14天后，平均矿化深度达到78μm。矿化28天后发现矿物质密度高达1.9 g/cm³，这与天然骨和牙本质相当。在干燥状态下，矿化水凝胶的弹性模量和硬度分别为20.3±1.7和0.93±0.07 GPa。水合后，它们分别降至4.50±0.55和0.10±0.03 GPa。这些值较低，但仍与天然硬组织处于同一数量级。结果表明，使用ELR的有机模板可以实现具有可控形态的无机-有机杂化生物材料。值得注意的是，ELR的化学和物理性质可以调节，这可能有助于阐明生物体调节矿化过程的机制。
