Preparation And Antibacterial Activity Of Amphiphilic N-halamine Antibacterial Agents

Bacterial contamination caused by pathogens has seriously threatened human health.In recent years,researchers have made great breakthrough in antimicrobial field.Many research groups have devoted themselves to the design of N-halamine polymers for biocidal applications because N-halamines have excellent biocidal efficacy against a broad spectrum of microorganisms without causing environmental polution,high biocidal activity,long-term stability over a wide temperature and moisture range,and structural regenerability.However,in addition to a good antibacterial function,most of the polymer N-halamines was reported to be hydrophobic due to the nature of polymer N-halamines,which are undesirable when their antibacterial actions were studied.N-Halamines with high hydrophobicity could make themselves serious aggregation before they come to contact with bacteria in aqueous solution,as a result giving a poor biocidal activity.Analogously,a quite high hydrophilicity is also unwelcome because hydrophilicity polymer N-halamines could not be employed in water environment,which may result in the loss of N-halamines.Accordingly,much more efforts have been concentrated on design of an amphiphilic polymer N-halamine,combining both hydrophilicity and hydrophobicity moieties into one entity.We chose methyl methacrylate(MMA)as the hydrophobic monomer,hydroxyethyl methacrylate(HEMA)as the hydrophilic monomer,and3-allyl-5,5-dimethylhexine(ADMH)as the N-halamines precursors.MMA is favorable to radical polymerization because ester group can stabilize the radicals and enhance the reactivity of ADMH toward chain propagation reaction,and HEMA is well known for its favorable hydrophilicity and good biocompatibility.These advantages make these three monomers easily prepared by polymerization of terpolymer,followed by a chlorination treatment using sodium hypochlorite as chlorinating agent.The main research contents are described as follows:1.A novel N-halamine terpolymer[i.e.,P(ADMH-MMA-HEMA)-Cl]with high antibacterial efficacies was fabricated via a free-radical copolymerization of3-allyl-5,5-dimethylhydantoin(ADMH),methylmethacrylate(MMA),and hydroxyethyl methacrylate(HEMA),followed by a chlorination treatment using sodium hypochlorite as chlorinating agent.In order to compare the antibacterial activity between amphiphilic terpolymer and bipolymers,P(ADMH-HEMA)-Cl and P(ADMH-MMA)-Cl were prepared by the same method.The chemical structure and morphology of the as-prepared polymer were analyzed by various characterization methods.The antibacterial activity of these synthesized N-halamines was assessed against Gram-positive bacteria(S.aureus)and Gram-negative bacteria(E.coli)by plate counting method and inhibition zone study.The antibacterial mechanism of these N-halamines is a contact/release co-determined mode.Antibacterial kinetics experiments showed that the antibacterial activity of these three N-halamines was time-dependent,compared to N-halamine biopolymer counterparts,the as-prepared N-halamineterpolymerP(ADMH-MMA-HEMA)-Clpresentedunexpected enhancement in antibacterial efficiency toward both pathogens.The MTT assay was performed to measure quantitatively the relative cell viabilities.The cell viability reached 90%even at the highest incubated concentration of 1000?g/m L,demonstrating the excellent biocompatibility of N-halamines.2.It has been well-known that electrospinning is a successful and efficient physical method to synthesize various composite fibers in antibacterial fields.The N-halamine fiber was fabricated for antibacterial applications using the amphiphilic terpolymer P(ADMH-MMA-HEMA)prepared above via electrospinning method.The as-prepared products were characterized by SEM,FITR,~1HNMR and XPS.As shown in SEM images,it is obvious to obtain quite intact and consequent fibers when the concentration of the solution was 47.7 wt%,moreover,the diameter distributions of N-halamines are in a quite narrow range of 1.2-2.5?m,which was ideal.The N-halaminefiberswerepreparedbytworouts:copolymerization-chlorination-electrospinningtechniqueand copolymerization-electrospinning-chlorination technique.SEM images showed that theN-halaminestructurewasformedby copolymerization-electrospinning-chlorination technique.The antimicrobial activity and antibacterial mechanism of N-halamine fiber was investigated by plate count method and inhibition zone study.The results showed that the N-halamine fiber has excellent antibacterical activity against S.aureus and E.coli,the bactericidal effect of S.aureus is better than E.coli.The antibacterial mechanism of N-halamine fiber:contact killing and release killing.Antibacterial kinetics experiments showed that the antibacterial activity of the N-halamine fiber was time-dependent and concentration-dependent.When the concentration is higher than 10 mg/mL and contact time is longer than 30 min,N-halamines fiber shows excellent antibacterial activity.