In Situ Synthesis of Chitosan Coated Silver-Zinc Oxide Nanocomposites and Its Enhanced Antibacterial Properties

The burgeoning antibiotic resistance of the bacteria has encouraged the researchers globally to develop new antimicrobial agents. Herein, we have developed nanocomposites (NCs) by coating chitosan (ch) onto the silver-zinc oxide nanocomposites through microwave assisted in situ approach, obtaining Ag@ZnO-ch NCs as a novel biopolymer coated antimicrobial agent. The surface morphology, crystalline structure and the functional groups of the nanocomposites were characterized by using field emission scanning electron microscopy (FE-SEM), X-ray diffraction measurements (XRD) and Fourier transform infrared spectroscopy (FTIR). The minimum inhibitory concentration (MIC) and the minimum killing concentration (MKC) of the Ag@ZnO-ch NCs showed excellent antibacterial activity towards both Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria recombinant green fluorescent protein (GFP) expressing antibiotic resistant Escherichia coli (E. coli). Further investigation of the antibacterial activity against the live water samples revealed that the Ag@ZnO-ch NCs treatment exhibited the similar antibacterial efficacy by inhibiting the bacterial growth. Also the MKC value of Ag@ZnO-ch NCs against S. aureus and GFP E. coli was 30 mu g/mL and 300 mu g/mL, respectively. Compared to the silver and zinc oxide based nanocomposites which have been widely used as antibacterial agents, our chitosan coated Ag@ZnO-ch NCs exhibited better antibacterial efficacy. Therefore, we proposed that the polymer coated metal-metal oxide nanocomposites is quite a promising antibacterial agent, suitable for the water purification applications.