Synthesis of sulfonated chitosan and its antibiofilm formation activity against E. coli and S. aureus.

A sulfonated chitosan (SCS) was prepared via nucleophilic substitution and characterized by Fourier transform infrared spectroscopy, H and C NMR spectra, gel permeation chromatography, elemental analysis, and thermo gravimetric analysis. The inhibition activities of bacterial adhesion and biofilm formation against E. coli and S. aureus of SCS were assessed in comparison with those of unmodified chitosan hydrochloride (WCS) which was commercially available. The metabolic activity and secretion of exopolysaccharide in biofilms of E. coli and S. aureus were significantly decreased after the treatment of SCS. Scanning electron microscopy and confocal laser scanning microscopy also demonstrated that SCS and WCS at 1MIC concentrations could obviously inhibit the formation of biofilm. Upon the experimental data obtained, it can be concluded that the alkylsulfonation of chitosan could significantly improve efficacy in killing biofilm-embedded bacteria, and the inhibition activities against biofilm formation of E. coli and S. aureus. The exploitation of SCS in this study is helpful to extend the understanding to an alternative to antibiotics and chemical preservatives in food and medicine fields.