Study On The Preparation Of Polymer Decorated LDH@Ag Nanohybrids And Their Antibacterial Properties

The pathogenic microorganisms have been a serious threat to human health and life.In the battle of humans against pathogenic bacteria,antibiotics were once considered a panacea for the treatment of the bacterial infections.But the emergence of bacterial resistance to antibiotics has greatly reduced the efficiency of antibiotic treatment and resulted in a new challenge to human health.Exploring new,cheap and effective antimicrobial agents has become an important research topic.The research and application of nanomaterials provide new opportunities for the development of novel antibacterial agents.Recent studies have shown that silver nanoparticles(AgNPs)have significant antibacterial activity against a variety of pathogens,drug-resistant bacteria and viruses.Although AgNPs have excellent antibacterial ability,its antibacterial effect is affected by many physical and chemical factors,such as particle size,shape and surface charge.In particular,AgNPs are easy to aggregate into larger particles,which leads to the decline of its antibacterial performance,thus affecting the application of silver based nano antibacterial agents.In this study,AgNPs were immobilized on the surface of polymer modified layered double hydroxides(LDH)to prepare highly efficient and stable silver-based nano antibacterial agents.The specific work includes the following two parts:1.The quaternized DMAEMA polymers were decorated on the surface of Mg Al-LDH as a support of silver nanoparticles to successfully construct a new type of nanohybrids(QPLDH-Ag).The physical and chemical properties of the synthesized materials were characterized and analyzed by scanning electron microscope(SEM),transmission electron microscope(TEM),fourier transform infrared(FTIR),UV Vis and X-ray photoelectron spectroscopy(XPS).At the same time,the antibacterial properties and antibacterial mechanism of QPLDH-Ag were analyzed.The results indicated that QPLDH-Ag showed good short-term and long-term antibacterial activity against Gram negative bacteria,Gram-positive bacteria and resistant bacteria.The antibacterial mechanism of QPLDH-Ag is mainly related to the destruction of bacterial cell membrane and the production of ROS.2.Based on the characteristics and advantages of LDH,PEI and AgNPs,we designed and synthesized a novel nanomaterial(d LDH-PDA-PEI-Ag)by using the strategy of mussel chemistry,and its physical and chemical properties were systematically characterized and analyzed.The results showed that the dispersion and stability of AgNPs were significantly improved on the polymer modified d LDH nanosheets.The prepared d LDH-PDA-PEI-Ag had good antibacterial activity against gram negative bacteria,gram positive bacteria and resistant bacteria,and the MIC values of d LDH-PDA-PEI-Ag against E.coli and S.epidermidis was 32 ?g/m L.In particular,d LDH-PDA-PEI-Ag has excellent cyclic antibacterial properties.After four cycles,the bactericidal rates against E.coli and S.epidermidis can still reach 100%and 96% respectively.The study of antibacterial mechanism showed that d LDH-PDA-PEI-Ag could kill bacteria mainly by damaging cell membrane and producing ROS.In addition,d LDH-PDA-PEI-Ag exhibited high catalytic activity for the reduction of methylene blue and p-nitrophenol.