Published 09/07/2018
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Historical perspective probing the threshold of membrane damage and cytotoxicity effects induced by silica nanoparticles in escherichia coli bacteria

F.Morote , T.Cohen-Bouhacina , C.Grauby-Heywang , L.Beven , I.Gammoudi , M.Mathelie-Guinlet , M.Delville , D.Moynet

Though, this enthusiasm began to be questioned as NPs might put environmental safety and human health at risk by interacting with biological systems and aecting their behavior at the cellular level. The diversity of NPs in terms of composition, shape and size/diameter () challenges politicians for regulating their safe use, and scientists for understanding how they interact with living organisms. Such regulation and understanding are, though, necessary for the safe development of various applications like diagnosis in medicine , smart textiles conception , environmental treatments and detection sensors. Among widely used biological systems, Escherichia coli is the most thoroughly studied species of bacteria. coli strains.
The engineering of nanomaterials, because of their specific properties, is increasingly being developed for commercial purposes over the past decades, to enhance diagnosis, cosmetics properties as well as sensing efficiency. However, the understanding of their fate and thus their interactions at the cellular level with bio-organisms remains elusive. Here, we investigate the size-and charge-dependence of the damages induced by silica nanoparticles on Gram-negative Escherichia coli bacteria. We show and quantify the existence of a NPs size threshold discriminating toxic and inert SiO 2-NPs with a critical particle diameter in the range 50nm80nm. This particular threshold is identified at both the micrometer scale via viability tests through Colony Forming Units counting, and the nanometer scale via atomic force microscopy. At this nanometer scale, AFM emphasizes the interaction between the cell membrane and SiO 2-NPs from both topographic and mechanical points of view. For SiO 2-NPs with > c no change in E. coli morphology nor its outer membrane organization is observed unless the NPs are positively charged in which case reorganization and disruption of the OM are detected. Conversely, when < c , E. coli exhibit unusual spherical shapes, partial collapse, even lysis, and OM reorganization.
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