Preparation And Antibacterial Activity Of Two Kinds Of Water-soluble Chitosan Derivative

The antibacterial materials is very important in the field of dealing with fabrics,processing operation wounds, fresh-keeping, antibacterial finishing of fabric and airpurification. The effects of most antimicrobial agents have been deprived because bacteria,fungi, and viruses produced resistance to antibiotics and chemical antibacterial drugs. It isvitally important to indagate the natural biomacromolecules antibacterial drugs.Chitosan (CS), an amino polysaccharide, is deacetylated from chitin. Chitosan isprovided with excellent own characters, such as biocompatibility, adsorptivity, hygroscopicity,antibacterial activity, low toxicity, biodegradability. Chitosan has extensive applications incosmetics, medicament, environmental protection and chemical industry. However, chitosancould not dissolve in water, alkali solution and most organic solvents, so its applications arelimited greatly. Therefore, the preparation of water-soluble chitosan derivative has the vitalsignificance.In this paper, we use chitosan as the crude material. The antibacterial activity of twokinds of water-soluble chitosan derivatives is our key point. The content is divided into threesections:Part1: The diverse low molecular weight chitosan was prepared by the method ofdegradation in hydrochloric acid, and test the degree of deacetylation by two abrupt changepotential titration method. Chitosan was modified by oleic acid as acylation reagents andchloroacetic acid as carboxymethyl reagents, then, the water soluble carboxymethyl chitosan(CMCS) and oleoyl-carboxymethyl chitosan (OCMCS) were successfully synthesized andcharacterized by FTIR and solubility test.Part2: Escherichia coli and Staphylococcus aureus, as typical bacteria, were investigatedfor the antibacterial activity of CMCS by the methods of turbidimetry. Then we evaluated theinfluence factors of antibacterial activity, such as concentration of CMCS, substituting degreeof carboxymethyl, molecular weight and pH of solution.Part3: OCMCS nanoparticles were prepared using an emulsifcation solvent evaporation method. E. coli and S. aureus were investigated for the antibacterial activity of OCMCSnanoparticles. Then, we test the influence of concentration of OCMCS nanoparticles,molecular weight, substituting degree of carbosymethyl and substituting degree of oleoyl tothe antibacterial activity.The results are as follows:(1) Chitosan with different molecular weight were prepared, and determined the viscosity.Then their molecular weight were calculated respectively36,135,375kDa. Their closedegree of deacetylation indicated that the degradation of chitosan did not impact on thedegree of deacetylation. FRIT spectroscopy demonstrated the molecular structure ofchitosan.(2) CMCS and OCMCS were soluble at neutral and alkalinity pH. FITR spectroscopyproved that the reaction was successful. Carbosymethyl and oleoyl were connected withchitosan molecular chains.(3) CMCS had distinctly antibacterial activity against E. coli and S. aureus. With theincrease of concentration, and the decrease of molecular weight and substituting degree ofcarbosymethyl, the antibacterial activity of CMCS was increase. When the pH of solution wasbetween7and8, CMCS had a nice antibacterial activity. CMCS solution formed a membranestructure around the bacteria cells, so nutritional matter could not exchange successfully.(4) The morphology of the OCMCS nanoparticles was observed by the transmissionelectron microscopy (TEM) method. The OCMCS nanoparticles was spherical in shape,regular and compact. The diameter of the OCMCS nanoparticles was about200nm.(5) The experiment indicated that when the concentration was higher than5mg/mL,OCMCS nanoparticles had antibacterial activity against E. coli and S. aureus. Theantibacterial activity was enhanced with the increase of concentration, molecular weight andsubstituting degree of oleoyl, and the decrease of substituting degree of carbosymethyl. Whenthe molecular weight was36kDa, substituting degree of oleoyl was10%, and substitutingdegree of carboxymethyl was60%, the OCMCS nanoparticles had the greatest antibacterialactivity. The minimal inhibitory concentrations were respectively10mg/mL,5mg/mL. Thephotos of TEM indicated that a part of nanoparticles bond to the bacteria cells, and another part of nanoparticles entered into the cells. Normal physiology activity of bacteria gotinterference.