Synergistic intrafibrillar/extrafibrillar mineralization of collagen scaffolds based on a biomimetic strategy to promote the regeneration of bone defects.

The mineralization of collagen scaffolds can improve their mechanical properties and biocompatibility, thereby providing an appropriate microenvironment for bone regeneration. The primary purpose of the present study is to fabricate a synergistically intra- and extrafibrillar mineralized collagen scaffold, which has many advantages in terms of biocompatibility, biomechanical properties, and further osteogenic potential. In this study, mineralized collagen scaffolds were fabricated using a traditional mineralization method (ie, immersed in simulated body fluid) as a control group and using a biomimetic method based on the polymer-induced liquid precursor process as an experimental group. In the polymer-induced liquid precursor process, a negatively charged polymer, carboxymethyl chitosan (CMC), was used to stabilize amorphous calcium phosphate (ACP) to form nanocomplexes of CMC/ACP. Collagen scaffolds mineralized based on the polymer-induced liquid precursor process were in gel form such that nanocomplexes of CMC/ACP can easily be drawn into the interstices of the collagen fibrils. Scanning electron microscopy and transmission electron microscopy were used to examine the porous micromorphology and synergistic mineralization pattern of the collagen scaffolds. Compared with simulated body fluid, nanocomplexes of CMC/ACP significantly increased the modulus of the collagen scaffolds. The results of in vitro experiments showed that the cell count and differentiated degrees in the experimental group were higher than those in the control group. Histological staining and micro-computed tomography showed that the amount of new bone regenerated in the experimental group was larger than that in the control group. The biomimetic mineralization will assist us in fabricating a novel collagen scaffold for clinical applications.

胶原蛋白支架的矿化可以改善其力学性能和生物相容性，从而为骨再生提供适宜的微环境。本研究的主要目的是制备一种纤维内和纤维外协同矿化的胶原蛋白支架，该支架在生物相容性、生物力学性能以及进一步的成骨潜力方面具有诸多优势。在本研究中，采用传统矿化方法（即浸泡在模拟体液中）制备矿化胶原蛋白支架作为对照组，采用基于聚合物诱导液态前体工艺的仿生方法制备的作为实验组。在聚合物诱导液态前体工艺中，使用带负电荷的聚合物羧甲基壳聚糖（CMC）来稳定无定形磷酸钙（ACP），以形成CMC/ACP纳米复合物。基于聚合物诱导液态前体工艺矿化的胶原蛋白支架呈凝胶形式，这样CMC/ACP纳米复合物能够轻易地被吸入胶原蛋白纤维的间隙中。利用扫描电子显微镜和透射电子显微镜来检测胶原蛋白支架的多孔微观形态和协同矿化模式。与模拟体液相比，CMC/ACP纳米复合物显著提高了胶原蛋白支架的模量。体外实验结果表明，实验组的细胞数量和分化程度均高于对照组。组织学染色和微型计算机断层扫描显示，实验组新生骨量多于对照组。仿生矿化将有助于我们制备一种用于临床应用的新型胶原蛋白支架。