Lipopolysaccharide Density and Structure Govern the Extent and Distance of Nanoparticle Interaction with Actual and Model Bacterial Outer Membranes

摘要

Design of nanomedidnes and nanoparticle-based antimicrobial and annfouling formulations and assessment of the potential implications of nanoparticle release into the environment requires understanding nanopartide interaction with bacterial surfaces. Here we demonstrate the electrostatically driven association of functionalized nanopartides with lipopolysaccharides of Gram-negative bacterial outer membranes and find that lipopolysaccharide structure influences the extent and location of binding relative to the outer leaflet-solution interface. By manipulating the lipopolysaccharide content in Shtwanella oneidensis outer membranes, we observed the electrostatically driven interaction of canonic gold nano-partides with the lipopolysaccharide-containing leaflet We probed this interaction by quartz crystal microbalance with dissipation monitoring (QCM-D) and second harmonic generation (SHG) using solid-supported lipopolysaccharide-containing Mayers. The association of canonic nanoparocles increased with lipopolysaccharide content, while no association of anionic nanopartides was observed. The harmonic-dependence of QCM-D measurements suggested that a population of the cationic nanopartides was held at a distance from the outer leaflet-solution interface of bilayers containing smooth lipopolysaccharides (those bearing a long O-polysaccharide). Additionally, smooth lipopolysaccharides held the bulk of the associated cationic particles outside of the interracial zone probed by SHG. Our results demonstrate that positively charged nanopartides are more likely to interact with Gram-negative bacteria than are negatively charged particles, and this interaction occurs primarily through lipopolysaccharides.