Biomacromolecules such as enzymes and proteins with bactericidal activity are promising for antibacterial applications in a mild, biocompatible, and environmentally friendly manner. However, low bactericidal efficiency has hindered its applications. Nanobiohybrids, constructed from biomacromolecules and functional nanomaterials, could enhance the function of biomacromolecules. However, the incompatibility between biological components and nanomaterials is still the major challenge of designing nanobiohybrids. Here, we rationally design lysozyme-Ag-polymer nanocomposites, which display high stability and antibacterial activity in a cooperative manner. The sufficient presence of Ag-N coordination between Ag and the polymer/protein contributed to the high stability of the nanocomposites. Compared with lysozyme and commercial silver nanoparticles (AgNPs) alone, the enzyme-Ag-polymer nanocomposites showed dramatically enhanced antibacterial activity. We propose a tightly encapsulated invasion (TEI) mechanism for a greatly improved antibacterial activity. The bacteria closely interacted with nanocomposites, and cell walls were hydrolyzed by lysozyme especially, facilitating the penetration of silver into the bacteria, and then reactive oxygen species (ROS) generated by silver to kill bacteria. In addition, the specific TEI mechanism resulted in high biocompatibility toward mammalian cells.
Keywords: antibacterial activity; enzyme; microbial infection; silver nanoparticles; synergistic effect.