Study On Photothermal Synergistic Enzymatic Catalysis Of Fe₃O₄ Nanoparticles As Antibacterial And Osteogenic Agent

During the treatment of orthopedic diseases,the defect parts of patients are very prone to infection,and the treatment of infectious bone defects has always been an urgent clinical problem.In response to this problem,effective bone tissue engineering materials should have two functions at the same time,one is to prevent bacterial infection,and the other is to promote regeneration and repair of bone defects.In the previous treatment methods,antibiotics are usually used to kill the bacteria at the defect site,and then bone repair materials are implanted to repair the bone defect.This treatment method has long treatment cycle,easy to cause bacterial drug resistance,and increases the risk of multiple infections.The development of multifunctional biomaterial scaffolds is expected to solve this complex problem.In bone tissue engineering,external field（force,electricity,magnetism,light）responsive scaffolds can promote bone regeneration through external physical stimuli.In addition,photothermal therapy and photodynamic therapy It is also typical of non-antibiotic treatment due to good thermal and oxidative damage.Based on this,this paper proposes a light-responsive bone cement scaffold with both therapeutic and repair functions using the excellent photothermal properties and enzyme-like catalytic ability of iron-based materials,which provides a solution for the treatment of infectious bone defects.In this study,a kind of Fe₃O₄ nanoparticles（IONPs）with good biocompatibility was prepared,which not only had excellent photothermal properties,but also had Fenton-like reaction in a wide p H range,and could be used as a photothermal-nanozyme catalysis synergistic antibacterial platform.In addition,iron oxide nanoparticles with photothermal response and catalytic properties were combined with calcium magnesium phosphate bone cement with good osteoinductive property to construct responsive bone repair scaffolds with therapeutic and repair functions.The main research work and results of this paper are as follows:1)Fe₃O₄ nanoparticles（IONPs）with good biocompatibility were prepared,which had excellent peroxidase-like catalytic activity and photothermal conversion ability,and could be used as a synergistic antibacterial platform of photothermal-nanozyme.IONPs can catalyze H₂O₂ to produce hydroxyl radicals in a slightly acidic environment,oxidizing bacterial cell membrane to damage bacteria.At the same time,its photothermal effect can not only produce hyperthermia to kill bacteria,but also enhance its enzyme-like catalytic capacity.After IONPs treatment,the antibacterial rate of Escherichia coli and Staphylococcus aureus reached nearly 100%.It also has obvious killing effect on bacteria in infected wounds of mice and can effectively promote the healing of infected wounds.2)CMPC@IONPs composite bone cement scaffold was prepared by mixing IONPs and calcium magnesium phosphate cement（CMPC）based on the synergistic effect of photothermal-nanozyme catalysis of IONPs.Studies have shown that CMPC@IONPs have good photothermal properties.In vitro cell experiments showed that CMPC@IONPs had good biocompatibility and promoted osteogenic ability.CMPC@IONPs could promote the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells when heated to 40.5+0.5℃under near-infrared irradiation.