Preparation And Resistant Bacteria Inhibition Of Silver Loaded Low Molecular Weight Chitosan Microspheres

Chitosan is an important natural material.It could be depolymerised into low molecular weight chitosan?LMWC?in high water soluble.Compared to chitosan,LMWC has higher antibacterial activity and better physiological functions.The silver nanoparticle loaded LMWC microspheres were efficient antibacterial agents obtained by LMWC compositing with silver nanoparticles.In this work,the degradation of chitosan with hydrogen peroxide in the simple homogeneous media was investigated.LMWC was dissolved in 1 wt%acetic acid aqueous solution,which is as the medium.The stable silver nanoparticles were prepared by the reduction of silver nitrate using vanillin as an reducing agent.The results indicated that Ag/LMWC colloidal sol can be prepared under the following conditions.The concentration ratio of AgNO₃ and vanillin is 1:5,the LMWC concentration is 3 wt%,theconcentration of AgNO₃ is 0.3 mol·L^-1,LMWC molecular weight is M?=43×104.The morphology of the silver nanoparticles in Ag/LMWC colloidal sol was characterized by Transmission electron micrographs?TEM??X-ray diffraction?XRD??Fourier transform infrared spectroscopy?FTIR?.The results positively indicated that the silver nanoparticles in the Ag/LMWC colloidal sol are all spherical with mean diameters in the range of 2?18nm and their crystal structure is face-centered cubic.The Ag/LMWC microspheres were prepared by emulsion cross-linking method with silver/LMWC colloidal sol as dispersed phase,liquid paraffin as continuous phase and sodium tripolyphosphate?STPP?as crosslinking agent.The results showed that Ag/LMWC microspheres can be prepared under the following condition.The concentration ratio of Span80 and OP-10 is 3:1,100 mL of liquid paraffin is as the continuous phase,the concentraion of emulsifier,silver/LMWC colloidal sol and STPP are 13.0 wt%,4.2 wt%and 13.6 wt%,respectively.The component of the resultant composite microspheres and the morphological structure of silver nanoparticles were characterized by Transmission electron micrographs?TEM?,Fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?patterns and so on.LMWC was dissolved in 1 wt%acetic acid solution,which is as the medium.The stable silver nanoparticles were prepared by the reduction of silver nitrate using pyrrole?Py?as an reducing agent.The results indicated that silver/PPy/LMWC colloidal sol can be prepared under the following conditions.The concentration ratio of AgNO₃ and Py is 1:3,the LMWC concentration is 3 wt%,the concentration of AgNO₃ is 0.50 mol·L^-1 andLMWC molecular weight M?=43×104.The preparation conditions of Ag/PPy/LMWC microspheres is according to those of Ag/LMWC microspheres.The component of the composite microspheres and the morphological structure of silver nanoparticles were characterized by Transmission electron micrographs?TEM?,Fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?patterns and so on.The antimicrobial ability of LMWC and its nanocomposites on Escherichia coliand and Staphylococcus aureus were studied.The results showed that Ag/LMWC and Ag/PPy/LMWC composite microspheres exert more efficient antibacterial properties than the correspomding LMWC.The Ag/LMWC microspheres antimicrobial mechanisms were speculated.The results showed that the antibacterial properties of the composite microspheres are attributed to the synergistic effects of silver nanoparticles and LMWC.