Abstract
Extensive bone defect repair remains a clinical challenge, since ideal implantable scaffolds require the integration of excellent biocompatibility, sufficient mechanical strength and high biological activity to support bone regeneration. The inorganic nanomaterial-based therapy is of great significance due to their excellent mechanical properties, adjustable biological interface and diversified functions. Calcium–phosphorus compounds, silica and metal-based materials are the most common categories of inorganic nanomaterials for bone defect repairing. Nano hydroxyapatites, similar to natural bone apatite minerals in terms of physiochemical and biological activities, are the most widely studied in the field of biomineralization. Nano silica could realize the bone-like hierarchical structure through biosilica mineralization process, and biomimetic silicifications could stimulate osteoblast activity for bone formation and also inhibit osteoclast differentiation. Novel metallic nanomaterials, including Ti, Mg, Zn and alloys, possess remarkable strength and stress absorption capacity, which could overcome the drawbacks of low mechanical properties of polymer-based materials and the brittleness of bioceramics. Moreover, the biodegradability, antibacterial activity and stem cell inducibility of metal nanomaterials can promote bone regeneration. In this review, the advantages of the novel inorganic nanomaterial-based therapy are summarized, laying the foundation for the development of novel bone regeneration strategies in future.
Highlights
Laboratory of Biomimetic Nanomaterials, Department of Orthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing
The mechanisms of mesoporous silica nanoparticles (MSNs) that promote bone defect reparation are as follows: (1) the silicon ions released by hydrolysis can promote the expression of osteogenic-related genes in osteoblasts (Figure 4a) [13]; (2) the mesoporous structure helps the deposition of HA, which further promotes mineralization [38]; (3) MSNs induce efficient macrophage uptake and promote immunomodulatory effects, which are conducive to osteogenic differentiation [39]
Zhu et al proved that shape- and size-controlled microgroove-patterned Ti surface structure manufactured by a combination of photolithography and inductively coupled plasma-based dry etching was beneficial to osteogenesis and bone regeneration [80]
Summary
Bone consists of inorganic minerals and organic matrix, and its highly hierarchical structure ensures excellent mechanical properties to withstand stress [1]. The ideal bone graft substitutes should imitate the extracellular matrix (ECM) of natural bone to achieve excellent biocompatibility, more importantly, they must provide strong mechanical support for the defect tissue. Inorganic nanomaterials possess better mechanical strength than natural and synthetic polymer scaffolds and can maintain stability for several weeks in vivo to support the bone healing process in the early stage of regeneration, making them the most promising candidate for bone graft substitutes. Nanomaterials 2021, 11, 789 process in the early stage of regeneration, making them the most promising candidate for bone graft substitutes. Nano silica has been proven to establish hierarchical widely studied due to their high similarity with natural bone apatite [5]. For metala been proven establish hierarchical structure anda promote bone regeneration materials, traditional bulk metal scaffolds have been used for permanent and temporary biosilicification process [6]. The the above three kinds of inorganic nanomaterials in bone tissue engineering will be readvantages and applications of the above three kinds of inorganic nanomaterials in bone viewed (Figure 1). will be reviewed (Figure 1)
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