Structural characterization and antimicrobial activity of chitosan/betaine derivative complex

Complex of chitosan acetate (CSAC) with C12–C18 alkyl amido prophyl dimethylamine betaine (AAPDB) was prepared and characterized by Fourier transform-infrared (FT-IR), thermal analysis (TG, DTG and DSC), X-ray diffractogram. Results showed that complex formed mainly by the electrostatic interaction between NH3+ of CSAC and COO− of AAPDB. Minimum inhibitory concentrations (MICs) were evaluated against E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis and Candida albicans. Results showed that CS/AAPDB solution could or even more strongly inhibit growth of all the tested microorganisms, whereas CSAC could not inhibit growth of C. albicans and AAPDB could not inhibit growth of S. epidermidis, E. coli, P. aeruginosa. Relative inhibition times (RITs) of CS/AAPDB solutions with different concentration and ratio of CSAC and AAPDB were also investigated against the five microorganisms. Results showed that CS/AAPDB solutions with CCSAC+CAAPDB of 0.05%+0.015%, 0.05%+0.0075%, and 0.025%+0.0075% showed higher antimicrobial activity. The relationship between complex formation and antimicrobial activity was discussed.