Recently, Southern University of Science and Technology Department of Materials Science and Engineering Associate Professor Ren Fuzeng's research group has made a series of research progress in biomedical orthopedic implant materials, and published 5 consecutive papers in internationally renowned journals.
Due to the aging population, accidents and bone tissue disease and other reasons, countless bone-damaged patients need surgery each year, bone repair biomaterials and implanted instruments are An important means to protect human health. Therefore, the development of new materials for bone tissue repair, replacement or promotion of bone tissue regeneration is very important, and it plays an important role in saving tens of thousands of critically ill patients, improving the quality of life of patients, and reducing medical costs.
Natural bone has a very delicate anisotropic structure. At the nanometer scale, hydroxyapatite (HA) crystals are distributed orderly in the gaps of collagen fiber bundles, and then assembled layer by layer to obtain a multi-level organic/inorganic composite structure. This fine and orderly directional structure endows bone tissue with excellent mechanical properties and biological functions. How to realize this complex fine hierarchical structure and biological function in artificial materials has important scientific significance and application value for designing bone repair materials that are compatible with natural bone mechanics and biology and improving the osseointegration after implantation. Similar to natural bone, wood is a natural anisotropic multi-level assembly material. The oriented cellulose fibers act as the skeleton, and the lignin and hemicellulose act as the binder, which together form the "reinforced concrete" microstructure of the wood, giving the wood superior mechanical properties. Inspired by the anisotropic multi-level structure of natural bone and wood, the research team developed a bionic design strategy "from wood to artificial bone". First, the natural wood was delignified to obtain a porous lignocellulose template, and then reused The vacuum infiltration method impregnates the alginate solution into the pores of the template, and deposits HA nanocrystals in situ after crosslinking to obtain a HA-wood-hydrogel composite material with a high degree of orientation. The research results show that the tensile strength of the composite material along the fiber orientation is as high as 67.8 MPa and the compressive strength is as high as 39.5 MPa.Exceeds most current strong hydrogels. In terms of microstructure, HA nanoparticles are deposited in the interstices of the fiber skeleton in an orderly manner, simulating the organic/inorganic composite structure and composition of collagen fibers and HA grains in bone tissue, successfully inducing the directional adhesion of cells and promoting the bone orientation of cells Differentiation. The results of animal implantation experiments show that this composite scaffold material can significantly accelerate the formation of new bone at the interface of the scaffold and induce the growth of new bone into the scaffold, thereby improving the overall osseointegration of the scaffold. The research results were published in Advanced Functional Materials under the title "Bioinspired Highly Anisotropic, Ultrastrong and Stiff, and Osteoconductive Mineralized Wood Hydrogel Composites for Bone Repair".
Figure 1. The biomimetic design strategy of HA nanocrystalline/alginate hydrogel/wood composite and its potential application in bone repair
poor bone formation performance Infections related to implants are an important reason for the failure of orthopedic implants. Realizing the organic unity of promoting osteogenesis and anti-bacterial infection on the surface of implants is a huge challenge for the surface modification of orthopedic implant materials. The research team constructed a high-resolution, controllable topological structure on the surface of medical titanium in the early stage, and used the material genome method to high-throughput screening of the surface topology and geometric dimensions that promote cell osteogenic differentiation (ACS Appl. Mater. On the basis of the research of Interfaces 2019, 11, 47, 43888–43901), in order to improve the osteoinductive and antibacterial properties, metal tantalum and tantalum copper nano-layer films were further deposited on the optimized topological titanium surface, and they were systematically studied. Effect on cell proliferation, differentiation, gene expression and antibacterial properties. The results show that the surface micro-nano topology can effectively regulate cell morphology and bone differentiation; tantalum and tantalum-copper films have good cell compatibility.It is suitable for cell adhesion, proliferation and differentiation, and has the function of anti-bacterial infection. In vivo implantation experiments further confirmed that the synergistic effect of the surface micro-nano topology and the tantalum-copper bilayer film can significantly induce bone formation and resist bacterial infection. This research is of great significance to the biofunctional design of medical metal surfaces. The research results were published in Advanced Healthcare Materials under the title "The synergy of topographical micropatterning and Ta|TaCu bilayered thin film on titanium implants enables dual-functions of enhanced osteogenesis and anti-infection".
Figure 2. The synergistic effect of micro-nano topology and Ta|TaCu double-layer nano-film on cell contact guidance and antibacterial mechanism schematic diagram
in the field of degradable metal scaffolds Iron has excellent mechanical properties, but its degradation rate is too slow; zinc has a moderate degradation rate, and its degradation products can be absorbed. However, compared with iron, zinc has low mechanical strength (especially when it has a three-dimensional porous structure), and porous zinc is difficult to prepare and the degradation mechanism in vivo is still unclear, which limits its application in bone repair materials. Based on this, the research team prepared a Fe@ Zn porous scaffold with a core-shell structure through template-assisted electrodeposition technology. Its pore structure and mechanical properties are similar to those of natural cancellous bone, and it has excellent antibacterial and antibacterial properties. Good effect of promoting bone repair. In addition, focused ion beam (FIB)-transmission electron microscopy (TEM) technology was used to analyze the degradation products of porous zinc in the body on a nanometer scale, and the degradation mechanism was clarified. This study proved the feasibility of Fe@Zn porous scaffold as a degradable orthopedic implant and provided direct evidence of the degradation products of zinc in vivo.The research results were published in Acta Biomaterialia under the title "Cancellous bone-like porous Fe@Zn scaffolds with core-shell-structured skeletons for biodegradable bone implants".
Figure 3. Schematic diagram of the preparation, in vivo, and in vitro research of Fe@Zn stent β-titanium alloy has great application potential as a bone repair material, but its mechanical properties do not match with natural bone, which easily causes stress shielding effect. Bone repair metal scaffold materials not only need to have a low elastic modulus close to that of human bone, but also need a higher yield strength and a certain degree of ductility to cope with the cyclic fatigue impact of the implant during long-term service. Therefore, how to obtain high yield strength while maintaining low modulus has become a major scientific problem. Moreover, this type of beta titanium alloy material contains a large amount of refractory elements, and the traditional process usually requires a long time homogenization treatment to solve the problem of uniformity of the structure. Its low cutting rate also brings about the processing of personalized implant materials. challenge. In recent years, 3D printing technology has shown significant advantages in the personalized customization of orthopedic implant materials. The research team used powder bed laser 3D printing technology combined with a low-cost in-situ alloying method to successfully prepare a uniformly structured Ti-12Mo-6Zr-2Fe alloy. By adjusting the molding parameters and post-processing technology, the microstructure of the molded part (including the preferred orientation of crystal grains, lattice defects and the composition of precipitated phases) is controlled, and excellent mechanical properties are obtained, and both high strength and low modulus are obtained. It provides a new choice for the preparation of high-performance biomedical titanium alloy implant materials, and is of great significance for the development of high-strength 3D printing β-titanium alloy materials. The research results were published in Additive Manufacturing under the title "A high strength and low modulus metastable β Ti-12Mo-6Zr-2Fe alloy fabricated by laser powder bed fusion in-situ alloying".
Figure 4. Processing schematic diagram, microstructure and mechanical properties of in-situ alloyed powder bed laser 3D printing β Ti-12Mo-6Zr-2Fe alloy
Niobium ( Nb ) has the advantages of corrosion resistance, wear resistance, high ductility, easy molding, low magnetic susceptibility, and compatibility with MRI. It is a potential orthopedic implant material. However, the traditional coarse-grained structure of niobium has low yield strength, lack of antibacterial properties, high melting point, easy to react with oxygen, high manufacturing cost and difficulty, which limits its wide application in orthopedic implant materials. Based on this, the research team prepared a nanostructured Nb-5 at.% Ag alloy through mechanical alloying and spark plasma sintering (SPS) technology. Compared with pure Nb, the compressive strength (1486 Mpa) and plasticity (35%) of the Nb-5 at% Ag alloy are significantly improved. The second phase of Ag precipitated on the Nb matrix not only greatly improves the tribological properties of the alloy, but also gives Nb strong antibacterial properties (antibacterial rate of 99%). Animal implantation experiments also confirmed the alloy's good biocompatibility, anti-infection function and osseointegrity. This Nb-based nanostructured alloy with good mechanical properties, corrosion resistance, biocompatibility and antibacterial properties is expected to become a new type of orthopedic implant metal material. The research results were published in the Journal of Materials Science & Technology with the title "A high strength, wear and corrosion-resistant, antibacterial and biocompatible Nb-5 at.% Ag alloy for dental and orthopedic implants".
Figure 5. Nanostructured Nb-5 at% Ag alloy exhibits excellent mechanical, anti-infection and osseointegration properties A communication unit,Ren Fuzeng is the corresponding author of the paper. The main contributors are: Department of Materials Science and Engineering Department, Research Assistant Professor Wang Xiaofei, Institute of Frontier and Interdisciplinary Sciences, Research Assistant Professor Fang Ju and He Jin, Department of Materials Science and Engineering, PhD students Zhu Mingyu, Duan Ranxi, Research Assistant Wan Tian, 2012 undergraduate student Chu Kangjie; the collaborators of the paper include Professor Zhao Yusheng of Southern University of Science and Technology, Southwest Jiaotong University Professor Lu Xiong, assistant professor Ye Dongdong of Wuyi University, and Professor Moataz M. Attallah of University of Birmingham. The above research work has been supported by the National Key Research and Development Program, the Guangdong Provincial Natural Science Foundation, the Shenzhen Basic Research Project, and the Southern University of Science and Technology Analysis and Testing Center imaging platform, micro-nano platform and laboratory animal center.
Links to related papers:
Links to papers: https://doi.org/10.1002/adfm.202010068
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Link to the paper: https://doi.org/10.1016/j.actbio.2020.11.032
Link to the paper:
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paper link:
https://doi.org/10.1016/j.jmst.2020.11.049
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