Construction Of Zinc-based Metal-organic Framework Composites Materials And Their Study Of Bacterial Infected Wound Healing

Objective:Facing the problems of antibiotic abuse and bacterial resistance,it is important to seek new antibacterial drugs that are highly effective in sterilization,economical and non-resistant to promote the improvement of wound nursing level.By constructing Zn-MOFs composites materials with simulated enzyme properties,exploring their therapeutic effects and mechanisms of action in infected wounds,and evaluating their in vivo and ex vivo biosafety,this project explores the possibility and application value of Zn-MOFs composites materials as new care products,and provides a more scientific solution for the care of clinical infected wounds.Methods:1.Preparation of zinc-based metal-organic framework composites materials and the evaluation of their simulated enzyme activityTwo different morphologies of Zn-MOFs（2D Zn-MOF and 3D Zn-MOF）were prepared using Zn²⁺as the metal central site;then gold nanoparticles（Au NPs）were loaded onto 2D/3D Zn-MOF to form 2D Zn-MOF@Au NPs and 3D Zn-MOF@Au NPs,respectively.The morphological characteristics and elemental compositions of the above materials were analyzed by scanning electron microscopy（SEM）and thermogravimetric analysis（TGA）tests;the mimetic peroxidase（CAT）activities of different materials were systematically investigated using bubble experiments and electrochemical analysis;the mimetic peroxidase（POD）activities of different materials were further compared by UV spectrophotometry and catalytic kinetics;the catalytic mechanism was investigated using terephthalic acid（TA）as a·OH trapping agent to investigate the catalytic mechanism of 2D/3D Zn-MOF@Au NPs.2.Evaluation of antibacterial properties of zinc-based metal-organic framework composites materialsBased on the simulated enzyme activity of 2D/3D Zn-MOF@Au NPs,their antibacterial effects against methicillin-resistant Staphylococcus aureus（MRSA）and Escherichia coli（E.coli）were investigated by growth inhibition assay and spread plate method;and the changes of bacterial structure and physiological functions were observed by Live/Dead bacterial staining assay and bacterial scanning electron microscopy assay.CCK-8 toxicity assay was selected to evaluate the in vitro biotoxicity of the Zn-MOFs composites materials with the most excellent catalytic performance at the cellular level.3.Zinc-based metal-organic framework composites materials for promoting bacterial infectious wound healingMRSA was selected to construct a mouse model of skin excision wound infection,and hydrogel dressing containing 3D Zn-MOF@Au NPs was applied to infected wounds of mice,and the data related to the promotion of wound healing by the material were obtained through the degree of wound healing,weight change,H&E and Masson staining analysis of skin tissue sections and pathological examination of major organs;healthy mice were injected intravenously with a certain concentration of 3D Zn-MOF@Au NPs aqueous solution,and the in vivo biocompatibility of the material was determined by blood biochemical indexes and pathological tissue analysis.Results:1.Preparation of zinc-based metal-organic framework composites materials and the evaluation of their simulated enzyme activity3D Zn-MOF exhibits a polyhedral structure in appearance,while 2D Zn-MOF is a uniform ultra-thin nanosheet;Au NPs are successfully loaded on the surface of 3D Zn-MOF with uniform size,without damaging the morphological structure of 3D Zn-MOF itself;while 2D Zn-MOF@Au NPs are flocculently stacked with the edges were blurred and the structure was changed,making it difficult to judge the bonding effect between the two.The structural stability of3D Zn-MOF@Au NPs in electrochemical detection and UV spectrophotometric experiments brought excellent CAT-like activity and mimetic POD enzyme activity;by the measurement of enzyme kinetic parameters,3D Zn-MOF@Au NPs had smaller Km values and larger Vmax values than 2D Zn-MOF@Au NPs,indicating that 3D Zn-MOF@Au NPs had stronger affinity and catalytic activity for the substrate than 2D Zn-MOF@Au NPs;by the test of the proposed POD activity product,3D Zn-MOF@Au NPs catalyzed a stronger·OH signal from low concentration H₂O₂ solution than 2D Zn-MOF@Au NPs.2.Evaluation of antibacterial properties of zinc-based metal-organic framework composites materialsThe results of growth inhibition and spread plate experiments showed that3D Zn-MOF@Au NPs in combination with low concentration of H₂O₂ solution could exert efficient antibacterial activity and kill both MRSA and E.coli more significantly.Live/Dead bacterial staining experiments and bacterial scanning electron microscopy experiments also further showed that·OH can disrupt bacterial structure and physiological functions,causing changes in cell membrane permeability and eventually leading to bacterial death.The antibacterial activity results of 2D/3D Zn-MOF@Au NPs were consistent with their mimetic enzymatic activity,and 3D Zn-MOF@Au NPs could more significantly enhance their antibacterial ability by catalyzing the production of·OH with high bactericidal activity by H₂O₂.3.Zinc-based metal-organic framework composites materials for promoting bacterial infectious wound healing3D Zn-MOF@Au NPs was able to effectively promote wound healing in infected wounds while avoiding the use of high concentrations of H₂O₂ by virtue of its good enzyme-mimetic catalytic activity;the results of H&E and Masson staining of the traumatized skin tissues showed that the trauma healing was relatively complete in the 3D Zn-MOF@Au NPs+H₂O₂ group,with no presence of inflammatory cells and a high degree of re-epithelialization;in vitro and in vivo biosafety results showed that the catalytic system with pro-bacterial activity was not found to be significantly toxic and had a high degree of biocompatibility.Conclusion:1.3D Zn-MOF@Au NPs has efficient simulated enzyme activity than 2D Zn-MOF@Au NPs,and the difference is closely related to the morphological structure of the material.3D Zn-MOF materials have a highly ordered porous structure,which makes the metal guest molecules（Au NPs）easily diffuse into the system and provide more active sites for the catalytic reaction.2.In vitro antibacterial experiments,3D Zn-MOF@Au NPs were able to decompose low concentrations of H₂O₂ into·OH with high antibacterial activity,which in turn affected the normal dynamic equilibrium within the bacteria,leading to morphological deformation and exudation of bacterial contents after the bacteria were continuously in an imbalanced state,and eventually complete death.3.Through the above antibacterial mechanism,the wound dressing containing 3D Zn-MOF@Au NPs with low concentration of H₂O₂ can achieve efficient killing effect by disturbing the level of reactive oxygen species inside the bacteria,and finally promote the wound healing of bacterial wound infection.The potential of 3D Zn-MOF@Au NPs in wound care is revealed,which provides a new idea for designing a novel care product.