Effects of Sub-lethal Concentrations of Silver Nanoparticles on a Simulated Intestinal Prokaryotic–Eukaryotic Interface (original) (raw)
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Effect of Biosynthesized Silver Nanoparticles on Bacterial Biofilm Changes in S. aureus and E. coli
MDPI nanomaterials, 2022
One approach for solving the problem of antibiotic resistance and bacterial persistence in biofilms is treatment with metals, including silver in the form of silver nanoparticles (AgNPs). Green synthesis is an environmentally friendly method to synthesize nanoparticles with a broad spectrum of unique properties that depend on the plant extracts used. AgNPs with antibacterial and antibiofilm effects were obtained using green synthesis from plant extracts of Lagerstroemia indica (AgNPs_LI), Alstonia scholaris (AgNPs_AS), and Aglaonema multifolium (AgNPs_AM). Nanoparticles were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. The ability to quench free radicals and total phenolic content in solution were also evaluated. The antibacterial activity of AgNPs was studied by growth curves as well as using a diffusion test on agar medium plates to determine minimal inhibitory concentrations (MICs). The effect of AgNPs on bacterial biofilms was evaluated by crystal violet (CV) staining. Average minimum inhibitory concentrations of AgNPs_LI, AgNPs_AS, AgNPs_AM were 15 ± 5, 20 + 5, 20 + 5 μg/mL and 20 ± 5, 15 + 5, 15 + 5 μg/mL against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, respectively. The E. coli strain formed biofilms in the presence of AgNPs, a less dense biofilm than the S. aureus strain. The highest inhibitory and destructive effect on biofilms was exhibited by AgNPs prepared using an extract from L. indica.
Interaction of silver nanoparticles withEscherichia coliand their cell envelope biomolecules
Journal of Basic Microbiology, 2013
The antibacterial effect of AgNPs was investigated by determining MIC/MBC and growth kinetics assay. The lowest MIC/MBC was found to be in the range of 11.25-22.5 mg ml À1. The growth kinetics curve shows that 25 mg ml À1 AgNPs strongly inhibits the bacterial growth. Confocal laser scanning electron microscopy (CLSM) shows that as the concentration of NPs increases, reduction in the number of cells was observed and at 50 mg ml À1 of NPs, 100% death was noticed. Scanning electron microscopy (SEM) shows cells were severely damaged with pits, multiple depressions, and indentation on cell surface and original rod shape has swollen into bigger size. High resolutiontransmission electron microscopic (HR-TEM) micrograph shows that cells were severely ruptured. The damaged cells showed either localized or complete separation of the cell membrane. The NPs that anchor onto cell surface and penetrating the cells may cause membrane damage, which could result in cell lysis. The interaction of AgNPs to membrane biomolecules; lipopolysaccharide (LPS) and L-a-phosphatidyl-ethanolamine (PE) were investigated by attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. LPS and PE showed IR spectral changes after AgNPs exposure. The O-antigen part of LPS was responsible for interaction of NPs through hydrogen bonding. The phosphodiester bond of PE was broken by AgNPs, forming phosphate monoesters and resulting in the highly disordered alkyl chain. The AgNPs-induced structural changes in phospholipid may lead to the loss of amphiphilic properties, destruction of the membrane and cell leaking. The biomolecular changes in bacterial cell envelope revealed by ATR-FTIR provide a deeper understanding of cytotoxicity of AgNPs.
Journal of Endodontics, 2014
Introduction: The purpose of this study was to evaluate the antibacterial efficacy of silver nanoparticles (AgNPs) as an irrigant or medicament against Enterococcus faecalis biofilms formed on root dentin. Methods: Dentin sections were inoculated with E. faecalis for 4 weeks to establish a standard monospecies biofilm model. These biofilms were tested in 2 stages. In stage 1, the biofilms were irrigated with 0.1% AgNP solution, 2% sodium hypochlorite, and sterile saline for 2 minutes, respectively. In stage 2, the biofilms were treated with AgNP gel (0.02% and 0.01%) and calcium hydroxide for 7 days. The ultrastructure of one half of the specimens from each group was evaluated by using scanning electron microscopy, whereas the structure and distribution of viable bacteria of the other half of the specimens were assessed with confocal laser scanning microscopy combined with viability staining. Results: Syringe irrigation with 0.1% AgNP solution did not disrupt the biofilm structure, and the proportion of viable bacteria in the biofilm structures was not different from that of the saline group (P > .05) but was less than that of the control group (P < .05). The biofilms treated with 0.02% AgNP gel as medicament significantly disrupted the structural integrity of the biofilm and resulted in the least number of post-treatment residual viable E. faecalis cells compared with 0.01% AgNP gel and calcium hydroxide groups (P < .05). Conclusions: The findings from this study suggested that the antibiofilm efficacy of AgNPs depends on the mode of application. AgNPs as a medicament and not as an irrigant showed potential to eliminate residual bacterial biofilms during root canal disinfection. (J Endod 2014;40:285-290) of coconut water, propolis, HBSS, and milk on PDL cell survival. J Endod. 2008 34(5):587-9.
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 2018
Since ingestion is one of the main routes of entry of nanoparticles (NPs) in our organism, simple and fast in vitro models of the intestinal barrier can be helpful to evaluate NPs risk. The human colon adenocarcinoma Caco-2 cell line has been extensively used due to its ability to differentiate, forming a well-structured cell monolayer. In this study, we have used these differentiated cells as a model of intestinal barrier to evaluate a wide set of effects caused by exposure to silver nanoparticles (AgNPs) with an average size of 7.74 nm. Different parameters such as toxicity, monolayer integrity and permeability (assessed by changes in cells' morphology and gene expression pattern), internalization (uptake), translocation, and induction of DNA damage (DNA breaks and oxidative DNA damage) were evaluated. No significant effects were observed on the monolayer's integrity/permeability after exposure to silver nanoparticles, although cellular uptake was demonstrated by using con...
Frontiers in Microbiology
Among all the food-related nanoparticles consumed every day, silver nanoparticles (AgNPs) have become one of the most commonly utilized because of their antimicrobial properties. Despite their common use, the effects of sublethal concentrations of AgNPs, especially on gut biofilms, have been poorly investigated. To address this issue, we investigated in vitro the proteomic response of a monospecies Escherichia coli gut biofilm to chronic and acute exposures in sublethal concentrations of AgNPs. We used a new gel-and label-free proteomic approach based on shotgun nanoflow liquid chromatography-tandem mass spectrometry. This approach allows a quantification of the whole proteome at a dynamic range that is higher than the traditional proteomic investigation. To assess all different possible exposure scenarios, we compared the biofilm proteome of four treatments: (i) untreated cells for the control treatment, (ii) cells treated with 1 µg/ml AgNPs for 24 h for the acute treatment, (iii) cells grown with 1 µg/ml AgNPs for 96 h for the chronic treatment, and (iv) cells grown in the presence of 1 µg/ml AgNPs for 72 h and then further treated for 24 h with 10 µg/ml AgNPs for the chronic + acute treatment. Among the 1,917 proteins identified, 212 were significantly differentially expressed proteins. Several pathways were altered including biofilm formation, bacterial adhesion, stress response to reactive oxygen species, and glucose utilization.
Nanotoxicology
A c c e p t e d M a n u s c r i p t Time-resolved toxicity study reveals the dynamic interactions between uncoated silver nanoparticles and bacteria It is still unclear whether the toxicity of silver nanoparticles (AgNPs) can be attributed solely to the release of Ag + or whether dissolved and nanoparticulate Ag act in parallel; this is due to the difficulty in distinguishing Ag +-from AgNP-effects. Also, AgNPs undergo changes during toxicity tests. This is the first study to investigate the influence of AgNP dissolution over time on viable counts at high time resolution and low cell density, avoiding the apparently reduced toxicity at higher cell densities identified in our study. Uncapped AgNPs were synthesized to avoid any interference from surface coatings. The transformations of AgNPs during storage were reduced. Lowering the concentration of AgNPs reduced their aggregation in Davis minimal medium (DMM). Also, AgNPs dissolved more slowly in DMM than in water. The minimum inhibitory concentrations (MICs) of Ag + and AgNPs increased with cell density according to a power law, suggesting that binding to cells decreased effective concentrations. However, AgNPs acted as a reservoir of Ag, releasing new Ag + to maintain the Ag stress. The toxicity of AgNPs was dominated by dissolved Ag. Combining controlled conditions, high time-resolution and low cell density, we could demonstrate different roles of ionic and nano Ag in bacterial death caused by AgNPs.
Effects of silver nanoparticles and ions on a co-culture model for the gastrointestinal epithelium
Particle and fibre toxicology, 2016
The increased incorporation of silver nanoparticles (Ag NPs) into consumer products makes the characterization of potential risk for humans and other organisms essential. The oral route is an important uptake route for NPs, therefore the study of the gastrointestinal tract in respect to NP uptake and toxicity is very timely. The aim of the present study was to evaluate the effects of Ag NPs and ions on a Caco-2/TC7:HT29-MTX intestinal co-culture model with mucus secretion, which constitutes an important protective barrier to exogenous agents in vivo and may strongly influence particle uptake. The presence of the mucus layer was confirmed with staining techniques (alcian blue and toluidine blue). Mono and co-cultures of Caco-2/TC7 and HT29-MTX cells were exposed to Ag NPs (Ag 20 and 200 nm) and AgNO3 and viability (alamar blue), ROS induction (DCFH-DA assay) and IL-8 release (ELISA) were measured. The particle agglomeration in the media was evaluated with DLS and the ion release with...
Journal of nanobiotechnology, 2016
The antimicrobial activity of silver nanoparticles (AgNP) has led to interest in their use in consumer products such as food contact materials, utensils, and storage containers. Incorporation of these materials into items intended for food processing and storage suggests that consumer use of these products could result in gastrointestinal exposure to AgNP, should the nanoparticles migrate from the product. The health impact of AgNP exposure is unknown, especially effects related to intestinal epithelial permeability and barrier function. This study examined the effects of AgNP exposure of different sizes (10, 20, 75 and 110 nm) and doses (20 and 100 µg/mL) on the permeability of T84 human colonic epithelial cells, which serve as an in vitro model of the human gut epithelium. Results showed that effects of AgNP on the T84 epithelial cells were size- and dose-dependent, with the 10 nm AgNP causing the most significant changes. Changes in permeability of the epithelial cell monolayer, ...
Journal of Advanced Veterinary Research, 2019
In Egypt, pseudomonas infection is one of the most important problems facing poultry production. Pseudomonas spp. is recognized as a major food spoiler and environmental contaminant. Biofilm formation by P. aeruginosa has an important role in the bacterial pathogenesis as well as persistence in the environment. The antibacterial and antibiofilm activities of AgNPs and NaOCL were evaluated against P. aeruginosa isolated from chicken farms. MIC and MBC of AgNPs against planktonic cells of P. aeruginosa were 15 and 20µg/ml, respectively. While those of NaOCL were 2200 and 2600 µg/ml, respectively. The highest inhibition percentages of biofilm formation (97.9%) was observed when P. aeruginosa treated with AgNPs (25µg/ml). While, 87.5% biofilm removal percentage was achieved after treating the established biofilm with 25 µg/ml AgNPs for 2.5 h. Moreover, NaOCL (2800 µg/ml) was able to cause 96.6% inhibition of biofilm formation and 90.3% biofilm removal after 1.5 h contact. The current st...
ACS Applied Materials & Interfaces
Understanding the interactions of silver nanoparticles (AgNPs) with the cell surface is crucial for the evaluation of bactericidal activity and for advanced biomedical and environmental applications. Biosynthesis of AgNPs was carried out through in situ reduction of silver nitrate (AgNO 3) by cell free protein of Rhizopus oryzae and the synthesized AgNPs was characterized by UV−vis spectroscopy, high resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), ζ-potential analysis, and FTIR spectroscopy. The HRTEM measurement confirmed the formation of 7.1 ± 1.2 nm AgNPs, whereas DLS study demonstrated average hydrodynamic size of AgNPs as 9.1 ± 1.6 nm. The antibacterial activity of the biosynthesized AgNPs (ζ = −17.1 ± 1.2 mV) was evaluated against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. The results showed that AgNPs exhibited concentration dependent antibacterial activity and 100% killing of E. coli and P. aeruginosa achieved when the cells were treated with 4.5 and 2.7 μg/mL AgNPs, respectively for 4 h. Furthermore, the intracellular reactive oxygen species (ROS) production suppressed the antioxidant defense and exerted mechanical damage to the membrane. AgNPs also induced surface charge neutralization and altered of the cell membrane permeability causing nonviability of the cells. Atomic force microscopy (AFM) studies depicted alteration of ultrastructural and nanomechanical properties of the cell surface following interaction with AgNPs, whereas FTIR spectroscopic analysis demonstrated that cell membrane of the treated cells underwent an order-to-disorder transition during the killing process and chemical composition of the cell membrane including fatty acids, proteins, and carbohydrates was decomposed following interaction with AgNPs.