| At present,bone defects caused by factors such as trauma,tumors or congenital deformities affected the bone health of millions of people every year.Although human bone tissue has endogenous self-healing and regeneration ability,the regeneration ability of bone tissue was limited and difficult to achieve.It was a huge challenge for both patients and orthopaedic surgeons to meet the repair of large-scale defects caused by tumors or trauma.Some patients generally use external fixation(plaster,fixation frame,etc.)to achieve fracture healing,while other patients often require implant fixation(stainless steel,titanium plate,screw,intramedullary nail,total hip joint,etc.)or bone graft repair materials(bone cement).,Bio-Oss bone meal,etc.)according to the severity of the patient’s condition.Bone repair material implantation(bone cement,Bio-Oss bone powder,etc.)filling treatment.Among them,Bone repair material was a high-quality utilization product,which was of great significance in both basic biomedical research and clinical practice in orthopaedics,which means that the requirements for bone repair materials were very strict.At the same time,the physical and biochemical coupling relationship between blood vessels and bones in bone healing has been paid attention to.In the early stage of bone healing,the growth of blood vessels was conducive to the delivery of nutrients and wastes,thereby better promoting bone tissue regeneration.Therefore,to develop biomaterials with better performance in the field of bone repair,the most important and challenging task was how to coordinate the regeneration of blood vessels and bone tissue in the process of bone repair.Therefore,how to prepare bone repair implant materials with excellent biosafety,osteogenic performance and angiogenesis was a key problem that needs to be solved urgently in orthopaedic clinical practice.In this paper,a LDHs-modified HAp scaffold composite was developed to realize the integrated repair of bone and blood vessels in bone tissue defects and promote bone tissue regeneration.Surface modification of hydroxyapatite(HAp)scaffolds by a facile one-step hydrothermal method,in situ growth of Mg-based LDHs doped with europium element to form the surface topography of micronano array structures and implanted in vivo.Afterwards,bioactive Mg and Eu ions were continuously released to promote cell adhesion and synergistic regeneration of bone and blood vessels.Subsequently,the key signaling pathway Wnt/β-catenin of the material in the process of bone repair was determined by gene sequencing,and the significant osteogenic differentiation/angiogenesis in vitro and the good bone defect repair performance in vivo of the LDHs-modified scaffold material were proved.1.Preparation and properties of europium-doped magnesium-based LDHs surface-modified HAp scaffold.Due to the lack of high biological activity,HAp scaffolds remain a great challenge in bone tissue engineering when used to treat disease-induced bone defects.Although hydroxyapatite(HAp)scaffolds have been considered as an attractive bone regeneration material,its poor biological activity greatly limits its wide application and could only play a role in osteoconduction.Here,we developed a multifunctional bioactive HAp scaffold(HAp/LDHs)of in situ grown Mg Al Eu-LDHs to confer excellent osteogenic differentiation/angiogenic properties to HAp scaffolds without adding additional cells or growth factor.First,we used a one-step hydrothermal method to grow europium-doped magnesium-based LDHs on HAp scaffolds,and set different hydrothermal times as controls to observe the changes of the growth amount of LDHs on HAp scaffolds with hydrothermal time.The hydrophilic properties and ion release properties of the HAp scaffolds with different hydrothermal times were further studied.The results showed that the experimental group with a hydrothermal time of 24 h had the best hydrophilicity,and the HAp/LDHs scaffold could maintain the ability to continuously release active ions for 35 days or even longer.Finally,we explored the adhesion ability of MC3T3-E1 cells(progenitor cells of mouse embryonic osteoblasts)on different scaffolds,and the results showed that the morphology of micro-nano structures could promote cell adhesion.This series of characterizations laid a good foundation for the further exploration of HAp scaffolds for in situ growth of LDHs in bone tissue engineering.2.Europium-doped magnesium-based LDHs surface-modified HAp scaffold for bone-vascular integrated repair.The HAp/LDHs scaffolds exhibited excellent biocompatibility during coincubation with two different cells,MC3T3-E1 and HUVEC,and exhibited potent osteogenic and angiogenic abilities in vitro.Alkaline phosphatase and alizarin red S staining showed that HAp had better osteogenic differentiation performance after in situ growth of europium-doped magnesium-based LDHs.Through the migration of HUVECs and Transwell crystal violet staining experiments,it was found that LDHs grown in situ had stronger angiogenesis ability,which may be related to the release of Eu ions during angiogenesis.The key Wnt/β-catenin signaling pathway of HAp/LDHs scaffold induced osteogenesis and angiogenesis was further revealed by gene sequencing,and the expression of related genes/proteins was verified by PCR and Western Blot.Finally,the osteogenic effect of HAp/LDHs scaffolds on bone defect repair was confirmed using a rabbit skull defect model.In summary,in this paper,the smooth surface of HAp was successfully modified by in situ growth of europium-doped magnesium-based LDHs,thereby promoting cell adhesion and enhancing its induction of osteogenic differentiation and angiogenesis.Furthermore,the key mechanism and signaling pathway of LDHs-modified HAp scaffolds in bone-vascular integrated repair was deeply explored,indicating that europium-doped magnesium-based LDHs surface-modified HAp scaffolds can be used as a surface-modified bone repair material with enhanced performance.It provides a brand new vision for implanted bone repair materials in bone-vascular tissue engineering. |
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