Abstract: Complexes of chitosan (CS) with Zn (II),Ni (II) and Co (II) were prepared,characterized by FT-IR and UV-vis spectra.The antibacterial activities of these complexes against Staphylococcus aureus and Escherichia coli were investigated in vitro.The results showed the antibacterial activities were dependent on the property of metal ions,and CS-Zn exhibited the best antibacterial activity.Hence,CS-Zn was selected to evaluate the antibacterial characteristic against E.coli.The integrity of the cell membrane and the permeability of the outer membrane (OM) were studied respectively,by determining the release from cells of material that absorb at 260 nm and changes in the fluorescence of cells treated with the fluorescent probe 1-N-phenylnaphthylamine (NPN).Transmission electron microscopy (TEM) analysis results indicated that CS-Zn disrupted bacterial cell membranes with the release of cellular content.

Key words: Chitosan-metal complexes, antibacterial activity, mechanism