AFM characterization of the effect of silver on bacterial membranes

CAROLINA DIAZ,; MICAELA BIANCHI; ALEJANDRO MIÑAN; DIEGO E. PISSINIS; P. L. SCHILARDI; LIA PIETRASANTA

Congreso; Congreso Internacional de Metalurgia Y Materiales SAM-CONAMET/IBEROMAT/MATERIA 2014; 2014

Bacterial resistance to antibiotics is considered one of the primary global risks facing the modern medicine. Novel approaches are required in order to improve antimicrobial efficacy. Silver nanomaterials exhibit broad spectrum biocidal activity toward bacteria, fungi, viruses and algae. This motivates its use in a large number of biomedical and environmental applications. Silver ions and nanoparticles have been strongly studied as an outstanding strategy to reduce microbial resistance to antibiotics. Nevertheless, the antibacterial mechanisms of silver nanomaterials are not yet fully elucidated. Some authors have proposed: silver ion release followed by cellular uptake and a cascade of intracellular reactions; extracellular and intracellular generation of reactive oxygen species (ROS) and direct interactions between silver and cell membranes. A detailed study of the effect of silver on bacterial membranes is important since it can be useful to explain the action mechanism of silver and to develop innovative antimicrobial therapies. Atomic force microscopy is a powerful tool to achieve these goals since it allows an exhaustive surface characterization of cell membranes and the possibility of develop a complete research of the nanomechanical properties. In the present work, we have studied the effect of silver ions and nanoparticles on Pseudomonas aeruginosa (Gram-) and Staphylococcus aureus (Gram-) since these microorganisms have structural differences in their cell walls. A detailed topographic characterization of bacterial cells before and after silver treatments has been performed. Also, we have study the change in nanomechanical properties of the microbial membranes in the presence of silver. Although significant progress has been made to elucidate the mechanisms of silver nanomaterial toxicity on microorganisms, further research is required to fully understand the processes involved and to safely exploit the tremendous antimicrobial properties of silver.