Preparation And Antibacterial Properties Of Carbon Quantum Dots And Their Application In The Treatment Of Infectious Bone Defects

Bone defect treatment is extremely prone to the risk of bacterial infection.In order to treat infected bone defects,it is necessary to implant a scaffold material with antibacterial properties to fill the infected bone defect site.Currently,scaffold materials with antibacterial properties are mainly prepared by loading antibiotics.However,some small molecule antibiotics are toxic and can even cause side effects such as allergic reactions in the body.In addition,it is difficult to cure infected bone defects with antibiotics,and large-scale use of antibiotics can also lead to the emergence of more lethal drug-resistant bacteria.Therefore,there is an urgent need to develop scaffold materials containing high-efficiency antibacterial materials with good biocompatibility and resistant to bacterial resistance for the treatment of infectious bone defects,and to achieve simultaneous treatment of antibacterial and bone repair.Carbon Quantum Dots(CQDs),as the smallest member of carbon nanomaterials,have low cytotoxicity,good photostability,and excellent biocompatibility.They are used in biosensing,bioimaging,optoelectronic devices,and pharmaceuticals.There are important potential applications in areas such as delivery and cancer treatment.In this paper,a high-efficiency microwave method was used to synthesize a new type of antibacterial carbon quantum dots with good biocompatibility and high antibacterial activity.The antibacterial carbon quantum dots and graphene quantum dots that promote bone differentiation are co-loaded on the hydrogel three-dimensional network to develop new anti-infective bone repair materials with dual functions of antibacterial and osteogenesis.The main research content of this article includes the following aspects:1.Preparation of antibacterial carbon quantum dots.In this thesis,a microwave synthesis method is used,spermidine is used as a precursor,and a rapid microwave reaction is carried out in the water phase to prepare a carbon quantum dot(a-CQD)with antibacterial activity rich in positive charge groups on the surface.The morphology and microstructure were characterized by various methods.The a-CQD yield is high,the fluorescence yield is high(34.3%),the lateral size is 4-5 nm,the interlayer spacing is 3.76?,and the Zeta potential is+39.4 m V.The surface of a-CQD contains a large number of amino groups and hydroxyl groups,exhibits positive charge characteristics,and has good water solubility.2.Research on the performance of antibacterial carbon quantum dots.The safety of carbon quantum dots was evaluated first,and there is almost no cytotoxicity at high doses(100?g/mL).Then the dilution coating plate method and growth curve method were used to evaluate their in vitro antibacterial performance.It was found that the carbon quantum dots have broad-spectrum antibacterial activity,and the minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus MRSA was 3?g/mL.Mechanism studies reveal the antibacterial mechanism of quantum dots that damage bacterial cell membranes.Finally,a wound model of MRSA infection in mice was constructed,and it was found that the carbon quantum dot antibacterial dressing has excellent antibacterial properties and can accelerate wound healing.3.Preparation of carbon quantum dot composite hydrogel material and its application in the treatment of infectious bone defects.In previous studies,we found that graphene quantum dots(p-CQD)with a negative surface charge have a good potential to promote bone differentiation.We have studied the co-loading of a-CQD and p-CQD for the treatment of infectious bone defects.However,since a-CQD has a strong positive charge and p-CQD has a negative charge,the direct mixing of the two will cause agglomeration of quantum dots,resulting in the failure of antibacterial and osteogenesis functions.In order to solve the problem of agglomeration and deactivation,we first load positively charged a-CQD onto the surface of negatively charged WS₂ nanosheets to obtain a-CQD/WS₂ composite material.The positive charge on the surface is greatly reduced,which can inhibit the aggregation between a-CQD and p-CQD,and the antibacterial activity did not decrease.Then,p-CQD and a-CQD/WS₂ were co-loaded into the gelatin Gel MA hydrogel to obtain the three-dimensional hydrogel/quantum dot composite material p-CQD/Gel MA/a-CQD-WS₂.The composite water was studied systematically.The gel's swelling,degradability,cytotoxicity,in vitro antibacterial,and in vitro osteogenic properties.The dilution coating plate test shows that the composite hydrogel has a good antibacterial effect,and the in vitro cell osteogenic differentiation experiment proves that the composite hydrogel has excellent osteogenesis effect.Finally,we constructed a mouse MRSA-infected bone defect model,implanted the composite hydrogel into the defect site,and imaged the skull with Micro-CT.The results showed that the composite material has a significant therapeutic effect on the repair of infectious bone defects.