Abstract
Although some metallic nanoparticles (NPs) are commonly used in the food processing plants as nanomaterials for food packaging, or as coatings on the food handling equipment, little is known about antimicrobial properties of palladium (PdNPs) and platinum (PtNPs) nanoparticles and their potential use in the food industry. In this study, common food-borne pathogens Salmonella enterica Infantis, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus were tested. Both NPs reduced viable cells with the log10 CFU reduction of 0.3–2.4 (PdNPs) and 0.8–2.0 (PtNPs), average inhibitory rates of 55.2–99% for PdNPs and of 83.8–99% for PtNPs. However, both NPs seemed to be less effective for biofilm formation and its reduction. The most effective concentrations were evaluated to be 22.25–44.5 mg/L for PdNPs and 50.5–101 mg/L for PtNPs. Furthermore, the interactions of tested NPs with bacterial cell were visualized by transmission electron microscopy (TEM). TEM visualization confirmed that NPs entered bacteria and caused direct damage of the cell walls, which resulted in bacterial disruption. The in vitro cytotoxicity of individual NPs was determined in primary human renal tubular epithelial cells (HRTECs), human keratinocytes (HaCat), human dermal fibroblasts (HDFs), human epithelial kidney cells (HEK 293), and primary human coronary artery endothelial cells (HCAECs). Due to their antimicrobial properties on bacterial cells and no acute cytotoxicity, both types of NPs could potentially fight food-borne pathogens.
Highlights
Food-borne pathogens are among the most common causes of bacterial contamination in food processing plants [1,2,3]
Bacteria generate the extracellular matrix consisting of extracellular polymeric substances (EPSs) such as exopolysaccharides, extracellular DNA, proteins and lipids which contribute to cell survival and the resistance of the biofilm mass to environmental conditions
The MIC was defined as the lowest substance concentration able to inhibit at least 80% of microbial growth (MICPC80 for planktonic cells, MICBC80 for further growth of biofilm cells), inhibit 80% of metabolic activity (MICBM80 for biofilm metabolic activity, MICMPB80 for metabolic activity of preformed biofilm), prevent biofilm formation by at least 80% (MICBF80 for biofilm formation), or reduce a preformed biofilm by at least 80% (MICBR80 for biofilm reduction)
Summary
Food-borne pathogens are among the most common causes of bacterial contamination in food processing plants [1,2,3]. Bacteria generate the extracellular matrix consisting of extracellular polymeric substances (EPSs) such as exopolysaccharides, extracellular DNA (eDNA), proteins and lipids which contribute to cell survival and the resistance of the biofilm mass to environmental conditions. These EPSs directly influence a variety of biofilm physico-chemical characteristics, such as its porosity, density, water content, permeability, absorption, hydrophobic properties, mechanical resistance and other properties [10,11,12]
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