Biomimetic mineralization of collagen fibrils is an essential process because the mineralized collagen fibers constitute the basic building block of natural bone. To overcome the limited availability and high cost of the noncollagenous proteins (NCPs) that regulate the mineralization process of collagen, commercially available analogues were developed to replicate sequestration and templating functions of NCPs. The use of branched polymers in intrafibrillar mineralization applications has never been explored. In this work, two novel carboxyl-rich brushlike polymers, a carboxylated polyethylene glycol terpolymer (PEG-COOH) and a polyethylene glycol/poly(acrylic acid) copolymer (PEG-PAA), were synthesized and modified to mimic the sequestration function of NCPs to induce intrafibrillar mineralization of collagen fibrils. It was found that these synthetic brushlike polymers are able to induce intrafibrillar mineralization by stabilizing the amorphous calcium phosphate (ACP) nanoprecursors and subsequently facilitating the infiltration of ACP into the gap zone of collagen microfibrils. Moreover, the weight ratios of mineral to collagen in the mineralized collagen fibrils in the presence of these brushlike polymers were 2.17 ± 0.07 for PEG-COOH and 2.23 ± 0.03 for PEG-PAA, while it is only 1.81 ± 0.21 for linear PAA. Plausible mineralization mechanisms using brushlike polymers are proposed that offer significant insight into the understanding of collagen mineralization induced by synthetic NCP analogues.

中文翻译：

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刷状聚合物诱导胶原纤维的原纤维内矿化作用增强

胶原蛋白原纤维的仿生矿化是必不可少的过程，因为矿化的胶原蛋白纤维构成了天然骨骼的基本组成部分。为了克服调节胶原蛋白矿化过程的非胶原蛋白（NCP）的有限可用性和高成本，开发了可商购的类似物来复制NCP的螯合和模板化功能。从未探索过支化聚合物在原纤维内矿化应用中的用途。在这项工作中，合成了两种新颖的富含羧基的刷状聚合物，即羧化聚乙二醇三元共聚物（PEG-COOH）和聚乙二醇/聚丙烯酸（PEG-PAA），以模仿NCP的螯合功能诱导胶原原纤维的原纤维内矿化。已发现这些合成的刷状聚合物能够通过稳定无定形磷酸钙（ACP）纳米前体并随后促进ACP渗入胶原微纤维的间隙区域来诱导原纤维内矿化。此外，在存在这些刷状聚合物的情况下，矿化胶原纤维中矿物质与胶原蛋白的重量比对于PEG-COOH为2.17±0.07，对于PEG-PAA为2.23±0.03，而对于线性PAA仅为1.81±0.21。提出了使用刷状聚合物的合理矿化机制，该机制为理解由合成NCP类似物诱导的胶原矿化提供了重要的见识。