Preparation Of Composite Nanosilve And Its Antibacterial Effect On Recombinant Luminescence Bacteria With Lux Gene

In this research,natural antibacterial agent chitosan and soluble starch with excell ent stability were used as protective agents.Silver nitrate was used as the silver precu rsor,and sodium borohydride was used as the reducing agent to prepare composite na nosilver particles according to the liquid phase reduction method.It performs an optim ized characterization analysis.To investigate the inhibitory effects of complex nanosilv er on the growth and luminescence of lux gene-labeled recombinant luminescent bacter ia E.coli DPD2794,E.coli TV1061,E.coli DH5?-P.luxCDABE and E.coli Top10-P.lux C DABE.The antibacterial performance and mechanism of composite nanosilver were ev aluated and evaluated.The conclusions were as below:?1?In the experiment,CS was used as the protective agent.The preparation condi tions were:HAc concentration 0.2%,CS concentration 0.5%,AgNO₃ concentration 0.05 mol/L,reaction time 1 h,reaction temperature 40?.The CS-AgNPs has maximum ultraviolet absorption peak at 409 nm.Its a disperse uniform spherical or ellipsoid ch itosan-silver nanoparticles with size range of 50-60 nm and uniform dispersion.FTIR analysis upheld the existence of nano-silver particles in the CS-AgNPs complex soluti on.Chitosan can protect the nano-silver particles from agglomeration by chelation.XR D indicated that silver crystals of CS-AgNPs are typical face-centered cubic crystal str ucture.?2?In the experiment,ST was used as the protective agent.The preparation condi tions were:ST concentration 1%,AgNO₃ concentration 0.05 mol/L,reaction time 1 h,reaction temperature 60?.The maximum UV absorption peak of ST-AgNPs is at 410 nm.It is a uniformly distributed core-shell spherical structure with a particle size of 20-30 nm.FTIR analysis showed that starch forms a protective layer on the surfac e of nano-silver,which can prevent the formation of agglomerated nano-silver particles.XRD showed that the ST-AgNPs were simple silver with a cubic structure and were almost free from impurities such as silver oxide,and the purity was high.?3?The order of inhibition of the four strains by composite nanosilver was E.coli DPD2794,E.coli TV1061,E.coli DH5?and E.coli Top10.The MIC of four strains o f CS-AgNPs were 60?g/mL,65?g/mL,80?g/mL,and 90?g/mL,respectively.The MIC of four strains of ST-AgNPs was 160?g/m L,175?g/m L,200?g/m L,and 215?g/mL,respectively.The antibacterial properties of chitosan and nanosilver synergistical ly increased,so its antibacterial activity was better than that of starch-nanosilver.?4?For inducible recombinant light-emitting bacteria E.coli DPD2794,high-concent ration composite nano-silver can inhibit cell luminescence.Composite nanosilver promo tes the luminescence of the recombinant bacteria When the amount of it added?1/16MIC.According to the luminescent mechanism,nano-silver can cause DNA damage to E.coli DPD2794 cell.For inducible recombinant light-emitting bacteria E.coli TV1061,high-concentration composite nano-silver??1/2 MIC?inhibited cell luminescence;low concentrations did not promote luminescence.However,it will delay the cultivation ti me for the maximum luminous intensity of the bacteria.For the constitutive recombin ant strains E.coli DH5?and E.coli Top10,the composite nano-silver has a uniform in hibition of its growth and luminescence.So it can reflect the toxicity of the nano-silv er by the luminescence property.After the composite nano-silver treatment,recombina nt bacteria showed cell deformity,damage,cell membrane rupture,and some intracellu lar substances dissolved.The results showed that the two kinds of composite nanosilve r had good antibacterial effect on four recombinant luminescent bacteria.