Study on the effect and mechanism of gold nanocoated magnesium bone scaffolds for bone repair

Background: Bone defects caused by trauma, tumors, and infections are common orthopedic diseases. Currently, the most commonly used treatment for bone defects is bone transplantation. Magnesium (Mg) and its alloys are widely used in orthopedic transplantation, but the rapid degradation rate is still a problem that needs to be considered when these materials are applied. The coating modification of magnesium metal surfaces via microarc oxidation (MAO) technology is an effective method for improving the corrosion resistance of Mg-containing implants, but it may reduce their antibacterial properties. Gold nanorods (AuNRs) have excellent antibacterial properties and the ability to regulate bone regeneration. The aim of this study was to construct a magnesium bone scaffold modified with gold nanoparticles and explore its role and mechanism in bone repair. Objective: The aim of this study was to construct a magnesium bone scaffold modified with gold nanoparticles and explore its role and mechanism in bone repair. Method: After screening the appropriate concentration of AuNRs was screened via cytotoxicity experiments, the gold nanoparticles were fixed on pure magnesium scaffolds after microarc oxidation through immersion coating and UV curing. Scanning electron microscope (SEM) was used to observe the microscopic morphology and pore structure characteristics of the surface of the magnesium bone scaffold. The magnesium bone scaffold modified with the gold nanocoating was immersed in phosphate buffer saline at a surface area/solution volume ratio of 1.25cm ² /ml, and then placed in a 37 ℃ constant temperature incubator. The supernatant was collected on days 3, 5, 10, and 15, and the changes in ion content were measured by the magnesium colorimetric method. At the same time, the scaffolds were removed and weighed in weeks 1, 2, 3, and 4 to determine the weight loss of the scaffolds and evaluate their biodegradability. The plates were coated with bacterial solutions co cultured with different materials from Staphylococcus aureus , and the antibacterial properties of the different groups of materials were observed by counting the number of bacterial colonies. MC3T3-E1 cells and vascular endothelial cells were used to validate the in vitro activity of the scaffold in promoting bone and vascular migration. The degradability and promotion of bone activity of the porous scaffolds and porous particles in vivo were evaluated in a rabbit distal femoral defect model. Create a Ø 2 × 5 mm cylindrical defect at the femoral condyle of 24 Sprague-Dawley rats was created, stent particles were implanted, and the rats were euthanized at 12 and 16 weeks to obtain femoral specimens. Various experiments were subsequently conducted on the samples, including histological section analysis. Result: The cell activity and biological properties were good at a concentration of 15 mg/ml AuNRs, which can be used for coating preparation. The SEM results demonstrated that the AuNR composite coating was successfully constructed on the surface of the magnesium bone material. In vitro magnesium ion release experiments revealed that the coating can delay the degradation of magnesium ions. The results of bacterial experiments revealed that the MAO magnesium bone scaffold modified with the AuNR coating had a significant antibacterial effect at 6 h and could reduce the occurrence of preclinical infections. The results of the cell culture experiments revealed that the MAO magnesium bone scaffold modified with the AuNR coating has good biological activity and osteogenic differentiation ability. In addition, animal experiments have shown that the MAO magnesium bone scaffold modified with the AuNR coating can significantly promote bone repair and increase bone integration between the implant and the bone. Conclusion: This study improved the corrosion resistance of magnesium bone scaffolds by constructing gold-containing nanocoatings on their surfaces and systematically evaluated their in vitro biodegradation behavior and in vivo osteogenic performance through a series of methods, promoting the osseointegration and osteogenic ability of internal plants and repairing bone loss sites. This study provides a new approach for the internal implantation treatment of patients with bone defects.