The Preparation And Antibacterial Research Of6-azido-quaternary Ammonium Chitosan And Its Derivatives

In order to obtain novel antibacterial materials and extend the antibacterialpotential of O-free-methyl-N, N, N-trimethyl chitosan quaternary ammonium salt(TMC) according to the antibacterial model of chitosan-polycationic derivatives,Different groups containing nitrogen (i.e. azide and ammonio group) were grafted tothe C6of TMC by sulfonylation reaction and nucleophilic substitution reaction in thispaper. The relationship between the structure of the newl antibacterial materials andantimicrobial activity against the gram-negative bacterium Escherichia coli (E. coli)and the gram-positive bacterium Staphylococcus aureu (S. aureus) were investigatedas well.First of all, two methyls were introduced into C2-NH2of chitosan by usingEschweiler-Clarke reaction to prepare the highly substituted N, N-dimethyl chitosan(DMC). Then DMC was reacted with the Methyl iodide (methylation reagent) toobtain quaternized TMC. And6-paratoluenesulfonic ester-TMC (Ts-TMC), whichwas prepared by reacting C6-OH of chitosan with paratoluenesulfonyl chloride,took place nucleophilic substitution reaction with sodium azide, ethylenediamine andhexanediamine respectively to prepare6-azido-6-deoxidation-TMC (N3-TMC),6-ammoniaethylamine-6-deoxidation-TMC (EDA-TMC) and6-aminohexylamine-6-deoxidation-TMC (HMDA-TMC). The synthesized products were characterizedby FTIR,1H NMR and elemental analysis.The antibacterial activity of the four quaternized chitosan derivatives (Ts-TMC,EDA-TMC, HMDA-TMC and N3-TMC) was tested by the MIC (minimum inhibitoryconcentration) test using TMC as control. The experimental results showed that theantibacterial activity of Ts-TMC was slightly stronger than TMC, and the other threewere enhanced greatly. The antibacterial activity of the new chitosan derivatives wasincreased with the degree of substitution of C6increasing. And the antibacterialactivity of those was different under different pH, which suggesting pH dependence.There were higher antibacterial activity in the condition of low pH. The paper offered possible reasons for the enhancement of antimicrobial activity. That were asfollowing, the density of the potential positive charge and water solubility of the newmaterials were increased by introducing the containing nitrogen groups into the C6ofTMC, thereby the antibacterial activity was enhanced. It was consistent with thepolycation chitosan antimicrobial model. Besides, the HMDA-TMC had longermethylene chain, which changing oil/water partition coefficient and possessing morefreedom terminal amino groups, so it could anchor on the surface of cell membraneand disturb the function of the cell membrane of bacteria. N3-TMC with azido grouphad the strongest antibacterial activity above four products with the similar degree ofsubstitution. It mesned azido group was a potent antibiotic group.