METAL NANOSTRUCTURES AS ANTIBACTERIAL AGENTS

Abstract

This review outlines the antibacterial activity of metal nanostructures, including proposed mechanisms and possible adaptative mechanisms to counteract their toxicity against bacteria. For purpose of this review, metal structures include metal nanoparticles, stabilized metal complexes, polymer and metal oxide nanocomposites. Without the cell wall, the bacterial cell would undergo lysis. There is evidence that metal nanoparticles can directly damage bacterial cell wall, by release of ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force and efflux of intracellular components. In this chapter, several phenomena associated with cell damage will be explored. The influence of osmotic stress to the surface structure of bacterial cells cause pits and wrinkled protrusions, leading to increased permeability and cell death. Morphological changes induced in bacteria, such as disaggregation of colonies, cell disruption with loss of intracellular material and weakening of the cell wall will be also discussed. The cessation of cell division resulting in enlarged cells and reduction of cell surface to volume ratio will be reported in this chapter as adaptative strategies to counteract the toxicity of metals against bacteria. This review will point out some of the mechanism of action of metal nanostructures: reactive oxygen species (ROS) generated on the surface of particles, metal ions release, membrane dysfunction, particle internalization and cytolitic damage. Selectivity, binding site and strain specificity of metal nanostructures at cell wall, effect on bacterial growth and viability of bacteria will be also described as well as the results of our current research project in copper-polymer nanocomposites as antibacterial agent.