Novel quaternized chitosan containing β-cyclodextrin moiety: Synthesis, characterization and antimicrobial activity

A novel water-soluble β-cyclodextrin grafted with chitosan (CD-g-CS) was prepared by reacting chitosan with O-p-toluenesulfonyl-β-cyclodextrin (Ts-CD) under acidic condition. It was found that the degree of N-substitution (DS) was in the range of 5 ± 2% to 23 ± 2%. The DS increased with an increasing in molar ratio of Ts-CD. Quaternization of CD-g-CS was performed by using glycidyltrimethyl ammonium chloride (GTMAC) under mild acidic condition yielding the quaternary ammonium CD-g-CS derivative (QCD-g-CS). The degree of quaternization (DQ) was determined by 1H NMR spectroscopy and potentiometric titration. It was found that the DQ was in the range of 60 ± 1% to 80 ± 1% and depended on the DS. The DQ increased with decreasing DS. Antimicrobial activity of these QCD-g-CSs were determined by using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods against Candida albicans (C. albicans), Streptococcus mutans (S. mutans) and Streptococcus oralis (S. oralis) in accordance with the methods of the National Committee for Clinical Laboratory Standards (NCCLS). The results revealed that the antimicrobial activity of all QCD-g-CSs was dependent on the DS/DQ ratio and type of microorganisms. The QCD-g-CSs and QCS showed higher antimicrobial activity against C. albicans fungus than against S. mutans and S. oralis bacteria. Moreover, the QCD-g-CS with DS/DQ ratio of 0.38 showed higher antimicrobial activity than DS/DQ ratios of 0.06 and 0.15, and also QCS against C. albicans and S. oralis, while all DS/DQ ratios did not enhance any antimicrobial activity against the S. mutans.