Bone is a hierarchical tissue in which the extracellular matrix consists of hydroxyapatite (HAP) crystals embedded in the collagen matrix. Artificial bone regeneration remains a great challenge due to the difficulty of balancing the chemical composition, biological compatibility, and mechanical performance of the implant. Biomineralization starts from the formation of a hydrogel-like biomacromolecule matrix in many cases, while the mineralization of HAP often builds from amorphous calcium phosphate (ACP) nanoclusters. Inspired by these discoveries, here we use a hydrogel loaded with ∼1 nm sized polymer-stabilized ACP nanoclusters (cluster-loaded hydrogel) as an injectable bone regeneration material. The hydrogel is biocompatible and stabilizes the ACP clusters such that they could efficiently infiltrate into collagen fibrils leading to intrafibrillar mineralization of HAP nanocrystals. Ex vivo results reveal that the cluster-loaded hydrogel has an excellent bone affinity as well as provides a suitable environment for the proliferation and differentiation of bone cells. In vivo experiments with rat bone show that the cluster-loaded hydrogel can generate HAP-based fillings within bone defects with perfect bonding to the surrounding tissue and a mechanical performance comparable with native bone. The fluidity of the hydrogel is further beneficial by providing a feasible minimally invasive bone healing procedure via syringe injection. The discovery and utilization of the cluster-loaded hydrogel described here provide a promising bioinspired approach for bone tissue regeneration.

中文翻译：

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磷酸钙纳米团簇可注射水凝胶用于骨再生

骨是一种分级组织，其中细胞外基质由嵌入胶原蛋白基质中的羟磷灰石（HAP）晶体组成。由于难以平衡植入物的化学成分，生物相容性和机械性能，人工骨再生仍然是一个巨大的挑战。在许多情况下，生物矿化从水凝胶状生物大分子基质的形成开始，而HAP的矿化通常由无定形磷酸钙（ACP）纳米团簇形成。受这些发现的启发，此处我们将装有约1 nm尺寸的聚合物稳定的ACP纳米团簇（团簇负载的水凝胶）的水凝胶用作可注射的骨再生材料。离体结果表明，簇状负载的水凝胶具有出色的骨亲和力，并为骨细胞的增殖和分化提供了合适的环境。用大鼠骨骼进行的体内实验表明，簇状负载的水凝胶可以在骨缺损内生成基于HAP的填充物，与周围组织完美结合，并且具有与天然骨骼相当的机械性能。水凝胶的流动性通过经由注射器注射提供可行的微创骨愈合程序而进一步有益。此处描述的簇状水凝胶的发现和利用为骨组织再生提供了有前途的生物启发方法。