Abstract
Nanotechnology applications are expected to bring a range of benefits to the food sector, aiming to provide better quality and conservation. In this research, the physiological response of both an Escherichia coli mono-species biofilm and Caco-2 intestinal cells to sub-lethal concentrations of silver nanoparticles (AgNPs) has been investigated. In order to simulate the anaerobic and aerobic compartments required for bacteria and intestinal cells growth, a simplified semi-batch model based on a transwell permeable support was developed. Interaction between the two compartments was obtained by exposing Caco-2 intestinal cells to the metabolites secreted by E. coli biofilm after its exposure to AgNPs. To the best of the authors’ knowledge, this study is the first to investigate the effect of AgNPs on Caco-2 cells that takes into consideration previous AgNP-intestinal biofilm interactions, and at concentrations mimicking real human exposure. Our data show that 1 μg/mL AgNPs in anaerobic conditions (i) promote biofilm formation up to 2.3 ± 0.3 fold in the first 72 h of treatment; (ii) increase reactive oxygen species (ROS) production to 84 ± 21% and change the physiological status of microbial cells after 96 h of treatment; (iii) seriously affect a 72-h old established biofilm, increasing the level of oxidative stress to 86 ± 21%. Moreover, the results indicate that oxygen renders the biofilm more adequate to counteract AgNP effects. Comet assays on Caco-2 cells demonstrated a protective role of biofilm against the genotoxic effect of 1 μg/mL AgNPs on intestinal epithelial cells.
Highlights
Because of their unique physico-chemical properties, nanoparticles (NPs) are widely used in the agri-food industry as agrochemicals for controlling pests and the delivery of active ingredients, nanosized ingredients, and additives (Chaudhry et al, 2008; Polo et al, 2011; Chen et al, 2016; Grillo et al, 2016)
In order to lay the foundation for understanding the complex interplay among NPs, gut biofilm and its host, the physiological response of a simplified system composed by Escherichia coli mono-species biofilm and Caco-2 intestinal cells exposed to sub-lethal concentrations of silver nanoparticles (AgNPs) was investigated
Intestinal E. coli biofilm was grown in a transwell device under anaerobic conditions, and the interaction between 1 μg/mL AgNPs, biofilm and Caco-2 cells was assessed by putting into contact the basolateral media containing the biofilm metabolites with Caco-2 cells grown with oxygen
Summary
Because of their unique physico-chemical properties, nanoparticles (NPs) are widely used in the agri-food industry as agrochemicals for controlling pests and the delivery of active ingredients, nanosized ingredients, and additives (Chaudhry et al, 2008; Polo et al, 2011; Chen et al, 2016; Grillo et al, 2016) Another interesting and growing nanomaterial application is for functionalizing food processing surfaces and for packaging, mostly to improve mechanical and antimicrobial properties (Dainelli et al, 2008). In order to lay the foundation for understanding the complex interplay among NPs, gut biofilm and its host, the physiological response of a simplified system composed by Escherichia coli mono-species biofilm and Caco-2 intestinal cells exposed to sub-lethal concentrations of silver nanoparticles (AgNPs) was investigated. The experiments were performed in the presence of 1 μg/mL AgNPs, the chosen representative of food-related, sub-lethal concentrations of human exposure (Gottschalk et al, 2013; Kuorwel et al, 2015; Fröhlich and Fröhlich, 2016)
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