Due to the soft and wet characteristics of hydrogels that acquire high mechanical strength by toughening strategies, tough and robust hydrogels are attractive as next-generation structural biomaterials, especially for the substitution of soft connective tissues such as cartilage, tendons, and ligaments. Firm fixation of the gels to bone in vivo is an indispensable technology in clinical applications. However, since the surface of the hydrogel is very watery, current medical adhesives cannot fix the gels at all. In this review, first, the double network (DN) strategy, a universal method to toughen hydrogels, is presented. Second, by combining hydroxyapatite (HAp) of a main bony inorganic component with a high-strength DN gel, a biocompatible adhesion method accompanied by spontaneous osteogenesis penetration into the gel matrix is introduced. In addition, the HAp-gel composite can be used as a simplified model of bone tissues because of their similarity in terms of components. Third, HAp formation spatially confined by the polymer network of gel is shown as a model of the earliest stage of biomineralization in vivo. These studies on biomineral–hydrogel composites have great potential to contribute not only basic research on osteogenesis mechanisms but also clinical applications of tough hydrogels. Double network (DN) gel - hydroxyapatite (HAp) composite achieves robust fixation to bone tissue accompanied by spontaneous osteogenesis penetration into the gel matrix. In addition, the HAp-DN gel composite can be used as a simplified model of bone tissues because of their similarity in terms of components. The HAp orientation is regulated by the anisotropy of the polymer network of gel, implying that the collagen matrix is oriented in the earliest stage of biomineralization in vivo .

中文翻译：

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坚固的水凝胶-生物陶瓷复合材料及其骨传导特性

由于水凝胶的柔软和湿润特性，通过增韧策略获得高机械强度，坚韧而坚固的水凝胶作为下一代结构生物材料具有吸引力，特别是用于替代软结缔组织，如软骨、肌腱和韧带。在体内将凝胶牢固地固定到骨骼是临床应用中不可或缺的技术。然而，由于水凝胶的表面非常水，目前的医用粘合剂根本无法固定凝胶。在这篇综述中，首先介绍了双网络 (DN) 策略，这是一种增强水凝胶的通用方法。其次，通过将主要骨无机成分的羟基磷灰石 (HAp) 与高强度 DN 凝胶相结合，引入了一种伴随自发成骨渗透到凝胶基质中的生物相容性粘附方法。此外，HAp-凝胶复合材料可用作骨组织的简化模型，因为它们在成分方面的相似性。第三，由凝胶聚合物网络空间限制的 HAp 形成显示为体内生物矿化最早阶段的模型。这些对生物矿物-水凝胶复合材料的研究不仅对成骨机制的基础研究，而且对坚韧水凝胶的临床应用都有很大的贡献。双网络 (DN) 凝胶 - 羟基磷灰石 (HAp) 复合材料实现了对骨组织的牢固固定，伴随着自发的成骨渗透到凝胶基质中。此外，HAp-DN 凝胶复合材料可用作骨组织的简化模型，因为它们在成分方面具有相似性。HAp 取向受凝胶聚合物网络的各向异性调节，