Study On Synthesis And Antibacterial Properties Of Co-MOFs And MOFs/Go Composites

The spread of pathogenic bacteria is threatening to human health and safety,so it shows great practical significance to design and develop high performance antibacterial materials.Metal-organic Frameworks（MOFs）are a kind of porous materials formed by self-assembly of metal ions or ion clusters and organic bridging ligands with nitrogen,oxygen donor atoms.Nowadays,it can be potentially used in the fields of adsorption storage,ion exchange,catalysis,biological medicine and so on.Because of satisfactory antibacterial activity of centre metal ions in some MOFs,excellent absorption capacity and drug delivery performance of MOFs derived from high specific surface area and various architectures,it provides a new direction for many researchers to develop high performance antimicrobial materials.In addition,some studies on antibacterial properties of graphene oxide（GO）show that GO is easy to be degradated and passivated owing to agglomeration,stacking or coated,which causes its passivation and declination of antibacterial properties.Therefore,it is of great scientific significance and research value to promote the research and application of new composite antibacterial materials by strategic compositing of MOFs and GO basing on their effective and synergistic antimicrobial properties.In this paper,four kinds of MOFs crystalline products were synthesized by using Cu²⁺,Zn²⁺,Co²⁺and different organic ligands.The antimicrobial activity of products was tested and evaluated by inhibition zone test,minimal inhibitory concentration（MIC）test and bacterial growth inhibition curve method,and the antibacterial mechanism was analyzed and discussed.Moreover,GO was prepared and composited with optimum MOFs.Morphology and structure of those composites were investigated,and their antibacterial activity was studied and analyzed.The main contents and findings are illustrated as follows:This work is supported by Key Research Project of Shaanxi Province（2018GY-125）and Innovation Ability Support Project of Shaanxi Province（2018PT-27）.（1）MOFs products（Zn-MOFs、Co-MOFs and Cu-MOFs etc.）were synthesized by solvent thermal method,and their morphologies and structures were analyzed and characterized by SEM,FT-IR and XRD and so on.The antibacterial activities of four complex crystals were tested and compared by using powder inhibition zone method.The results show that the Co-MOFs has good killing and inhibition effects against E.coli,P.aeruginosa,S.aureus and C.albicans,indicating better antibacterial activity among four products.（2）The sustained release and bactericidal ability of Co-MOFs was studied by adopting MIC and growth curve methodes.The stability and ion-release properties of Co-MOFs crystals were measured and analyzed.And the intrinsic relationship between material properties and antimicrobial activity was discussed.The results showed that the Co-MOFs had obvious antibacterial activity against all the tested bacteria,especially candida albicans.The sustained release experiments showed the high ion release of Co-MOFs at the initial stage（up to 70%at24h）and then sustain ion release continuing for 144 hours（6 days）.The analysis of antimicrobial activity showed a positive correlation with the amount of ions release.The main antibacterial effects were attribute to inhibition of bacterial cells division and proliferation,destroy of bacterial strain growth cycle and bacterial cell.The differences of antibacterial effect were due to the differences of growth cycle of bacterial strains and features of cell structures.（3）GO was prepared by employing improved Hummer’s method,and it was composited with Co-MOFs.The morphology and structure of GO and Co-MOFs/GO compounds were characterized by SEM,FT-IR and XRD and so on.The results of powder inhibition zone test showed the better antimicrobial performance of composite product than both of GO and Co-MOFs.The MIC values of Co-MOFs/GO composite against E.coli,P.aeruginosa,S.aureus and C.albicans were 384-499 ppm,38.4-153.6 ppm,19.2-38.4 ppm,and 19.2-38.4 ppm,respectively,which lower than those of the Co-MOFs,indicting remarkable enhancement on antimicrobial activity.