Copper-Based Metal-Organic Framework Materials For Bacterial Inhibition And Promoting Of Infectious Wound Healing

Object:Infectious wounds have become a global healthcare problem.The therapy is unsatisfactory because of time consumption of the process,bacterial resistance,high requirements of the biotherapy and other limitations,which bring the stress to the clinical and nursing system.There some reports indicate that increasing the level of reactive oxygen species（ROS）around the wound can achieve the effect of antibacterial and wound healing.A series of Metal-Organic Frameworks（MOFs）have received extensive attention in the biomedical field due to the excellent physical and chemical properties of controllable metal ions release and mimicking peroxidase activity which can catalyze the generation of ROS from substrates.In this work,we synthesized two types of MOFs with mimicking peroxidase activity serving as antibacterial materials.Furthermore,we evaluated their effects in bacterial inhibition,wound treatment,and biosafety in vivo to explore the potential of MOFs as a new therapeutic product of infectious wounds in clinical application.Methods:1.Synthesis of copper-based metal organic frameworks and the evaluation of their mimicking peroxidase activityTwo kinds of copper-based metal frameworks（Cu-MOFs）with different structure were synthesized.Cu-TCPP（2D）displayed two dimensional structure and HKUST-1（3D）presented three dimensional structure.The morphology were performed by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and so on.The mimicking peroxidase activity of Cu-MOFs was analyzed and compared by bubble formation test,electrochemical method,and UV-vis methods.Finally,the terephthalic acid was used to detect the hydroxyl radical（·OH）catalyzed by Cu-MOFs.2.Evaluation of antibacterial properties of copper-based metal organic frameworks for promoting bacterial infectious wound healingCu-MOFs with mimicking peroxidase activity were applied in antibacterial treatment and wound therapy.Their biosafety in vivo was evaluated.Two kind of clinical pathogen with Gram-negative bacteria of Escherichia coli（E coli）and Gram-positive of Methicillin-Resistant Staphylococcus Aureus（MRSA）were used in this experiment.A mouse model of bacterial infection with full-thickness skin excision was established for the evaluation of therapy effects.The antibacterial properties of Cu-MOFs was evaluated by spread-plate method,fluorescence staining and SEM images of bacteria.Hydrogel dressings containing HKUST-1 were employed to treat the bacterial wounds of mice.After 7 days of treatment,the general condition of the wound,healing rate,the skin tissue with hematoxylin-eosin（H&E）and Masson staining were hired to evaluate the wound healing.A certain concentration of HKUST-1suspension was injected into the tail vein of mice and the main organs were taken for H&E staining to assess the biosafety in vivo.Results:1.Synthesis of copper-based metal organic frameworks and the evaluation of their mimicking peroxidase activityThe morphology and characterization of Cu-MOFs proved the successful synthesis,which were consistent with the literature reports.Cu-TCPP exhibits an ultrathin two-dimensional sheet structure and HKUST-1exhibits a uniform octahedral structure.The mimicking peroxidase activity was studied by bubble formation test,electrochemical methods and UV-vis methods.The result of electrochemical experiment showed that electrode with HKUST-1 modification presented higher peak current response than Cu-TCPP modification which pointed out the efficient electrocatalysis and the selectivity of HKUST-1 towards H₂O₂.TMB chromogenic substrate showed that HKUST-1 exhibited better mimicking peroxidase activity than Cu-TCPP;the enzymatic kinetic parameters of HKUST-1 were determined,showing a lower Km value and good affinity for the substrate.The terephthalic acid was used in fluorescent experiment to detect hydroxyl radical（·OH）.The higher fluorescence intensity of HKUST-1 showing its efficient catalysis of H₂O₂for hydroxyl radicals（·OH）generation.2.Evaluation of antibacterial properties of copper-based metal organic frameworks for promoting bacterial infectious wound healingCu-MOFs was used for bacterial inhibition and wound treatment.HKUST-1 promoted the decomposition of H₂O₂,which can produces a large number of hydroxyl radicals（·OH）to sterilize bacteria effectively,displaying obvious inhibitory effect on Gram-negative and Gram-positive bacteria.Scanning electron microscope images and fluorescence staining showed the consistent results with the spread-plate experiments.The morphological structure and membrane of bacteria was destroyed,resulting in the death of bacteria.Vivo experiments showed that Cu-MOFs presented excellent effect to treat infectious wounds and promote wound healing.Besides,Cu-MOFs with good biosafety,and no obvious biological toxicity was found.Conclusion:1.HKUST-1 has better mimicking peroxidase activity and affinity for catalytic substrates than Cu-TCPP.The difference could be related to the morphology and structure of MOFs.The three-dimensional structure of HKUST-1 is conducive to electron transfer,accelerates the catalytic reaction rate,and catalyzes H₂O₂ efficiently,laying the foundation of the antibacterial property and wound healing.2.HKUST-1 promoted the decomposition of H₂O₂ to produce hydroxyl radicals,showing a broad-spectrum of antibacterial activity,promotion of infectious wounds healing,and good biosafety.For these results,it reveals the applications of Cu-MOFs in bacterial inhibition and wound therapy.It’s expected to develop new antibacterial therapeutic care products based on Cu-MOFs to provide more solutions for clinical wound treatment and care.