Construction Of Water-Soluble Metal Organic Frameworks And Their Antimicrobial Activity

Bacteria is helpful in many perspectives in our daily lives.They are used to decompose garbage,purify water,synthesize multivitamins,and so on.However,some bacteria can cause systemic infections,such as Helicobacter pylori,leading to gastritis,gastric ulcers,and even cancer in some patients.Therefore,a wide variety of antibiotics,such as lactam and glycopeptide and etc,are used in the clinical treatment of various bacterial infections.However,the cheap and easy availability of antimicrobial drugs makes them the most abused drugs,leading to the development of bacterial resistance.It is thus imperative to synthesize and screen new antimicrobial agents.In recent years,the antibacterial activity of new nanomaterials has attracted extensive attention.These materials include carbon nanotubes,graphene,hydrogels,and metal-organic frameworks(MOFs),etc.Among them,MOFs are of particular interest,mainly due to its good biodegradability.Through biodegradation in vivo,metal ions with antibacterial activity in MOFs are gradually released,effectively avoided toxicity raised from the high concentration of metal ions.However,the study on the antibacterial activity of MOFs is still in its infancy because of that most of the MOFs exhibit limited water solubility and stability and hinder their application in the biological field.In view of such research background,we have carried out several parts of work in this thesis and the details are summarized as follows.Screened from the permutative reactions of Ag(?),Cu(?),Zn(?)with a set of four kinds of quaternized carboxylic acid ligands of N-(carboxyethyl)-(3,5-dicarboxyl)_pyridinium bromide(H3CedcpBr),N-(carboxymethyl)-(3,5-dicarboxyl)-pyridinium bromide(H3CmdcpBr),4-carboxyl-(3,5-dicarboxy-benzyl)-pyridinium bromide(H3CdcbpBr),3-carboxyl-(3,5-dicarboxy-benzyl)-pyridinium bromide(H3CdcbpBr),and in the presence of auxiliary ligands of 4,4'-pyridine(bipy)and 1,10-phenanthroline monohydrate(phen),we have obtained 6 MOFs:[Ag2(Cedcp)]n(1),{[Ag4(Cmdcp)2(H2O)4]�4H2O}n(2),[Cu(Cdcbp)(bipy)(H2O)2]?(3),[Cu(Cdcbp)(bipy)(H2O)]n(4),[Cu(Cdcbp)2(phen)-4H2O]n(5)and[Zn(Cdcbp)2(bipy)2�H2O]n(6).MOFs 1-6 were characterized by infrared spectroscopy,elemental analysis,and X-ray single crystal diffraction.Single crystal structure showed that MOF 1 is three-dimensional(3D),whereas MOFs 2,3,4 and 6 features 2D structures,and MOF 5 exhibits a 1D structure.The metal ions in these MOFs were all layered with organic ligands and showed good water stability,which provided possibilities for the study of their antibacterial activity.Subsequently,the activity of 8 strains for 6 MOFs was screened by microbroth culture dilution method.Preliminary screening results showed that MOF 1 and 2 based on Ag(?)had significant antibacterial activity.The inhibition rate of MOF 1(18.68?M)for Propionibacterium acnes ATCC6919 was 86.86 � 0.16%,and for Staphylococcus aureus ATCC25923 was 87.67� 0.28%.In contrast,MOF 2 showed better antimicrobial activity,with over 70%inhibition rate against all kinds of bacteria,and favorably over 90%against Escherichia coli ATCC25922,Monilia albican ATCC2002,and Pseudomonas aeruginose ATCC27853.Finally,the antimicrobial activities of MOFs 1 and 2 were further studied.The SEM results of Staphylococcus aureus showed that the bacterial morphology changed significantly upon treatment with MOFs,which proved that MOF 1 and 2 had significant antibacterial activity.The hemolytic toxicity test results showed that the hemolytic toxicity of MOF 1 was very low,and the hemolysis rate was only 2.03� 1.08%at its highest concentration of 18.90 p.M,and 16.90� 2.34%for MOF 2 at its highest concentration of 10.04 NM with a dose-dependent(non-toxic)way.We further explored the minimum inhibitory concentration(MIC)for MOFs 1,2 and their components.The results showed that the MIC of MOF 1 for S.aureus ATCC25923 and P.acnes ATCC6919 are both 37.84.M,while MOF 2 for all strains are among 2.51-10.04 ?M,which are much lower than AgNO3.The two ligands involved in the synthesis of MOF 1 and 2 had no obvious antibacterial activity,indicat:ing that the formation of MOF 1 and 2 is necessary for their antibacterial eflfect and the activity is due to the release of Ag+.The E.coli sterilization kinetics experiment indicated that MOF 2 exerted its antibacterial activity in a very short time(60 min).Herein,6 water-soluble MOF materials were designed,synthesized,and screened for antimicrobial activities.The results showed that the MOFs based on Ag+ had better antimicrobial activities.Due to the limited number of synthesized MOFs,it is difficult to obtain a clear structure-activity relationship at present.Nevertheless,the study of this topic has cerctain guiding significance for our future synthesis and screening of novel MOFs for the study of antimicrobial activity.