Abstract: In order to improve the stability of lysozyme and its antibacterial activity against Gram-negative bacteria, as a green and highly efficient antibacterial agent, lysozyme-functionalized gold nanoparticles were prepared for the first time by surface modification of gold nanoparticles with lysozyme. The influences of the mass ratio of lysozyme to gold nanoparticles and the concentration of functionalized nanoparticles on the antibacterial activity against Gram-negative and Gram-positive bacteria were examined. The antibacterial mechanism of the prepared materials against Escherichia coli and the cytotoxicity on SH-SY5Y cells were also investigated. The results showed that compared with pure gold nanoparticles and lysozyme, the antibacterial activity of lysozyme-functionalized gold nanoparticles against E. coli and Staphylococcus aureus were obviously enhanced, which indicated the synergistic antibacterial effect of lysozyme and gold nanoparticles. Under optimized conditions, 0.1 g/L lysozyme-functionalized gold nanoparticles were able to completely kill the two types of bacteria. Besides, lysozyme-functionalized gold nanoparticles exhibited durable antibacterial properties and good biocompatibility, which were not toxic to mammalian cells. Transmission electron microscopy (TEM) images and live/dead bacterial assay showed that lysozyme-functionalized gold nanoparticles could kill bacteria by disrupting the cell membrane and cell wall.

Key words: lysozyme, gold nanoparticles, antibacterial activity, cytotoxicity, membrane permeability