Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles.

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SummaryDevelopment of reliable cell-based nanotoxicology assays is important for evaluation of potentially hazardous engineered nanomaterials. Challenges to producing a reliable assay protocol include working with nanoparticle dispersions and living cell lines, and the potential for nano-related interference effects. Here we demonstrate the use of a 96-well plate design with several measurement controls and an interlaboratory comparison study involving five laboratories to characterize the robustness of a nanocytotoxicity MTS cell viability assay based on the A549 cell line. The consensus EC 50 values were 22.1 mg/L (95% confidence intervals 16.9 mg/L to 27.2 mg/L) and 52.6 mg/L (44.1 mg/L to 62.6 mg/L) for positively charged polystyrene nanoparticles for the serum-free and serum conditions, respectively, and 49.7 µmol/L (47.5 µmol/L to 51.5 µmol/L) and 77.0 µmol/L (54.3 µmol/L to 99.4 µmol/L) for positive chemical control cadmium sulfate for the serum-free and serum conditions, respectively. Results from the measurement controls can be used to evaluate the sources of variability and their relative magnitudes within and between laboratories. This information revealed steps of the protocol that may need to be modified to improve the overall robustness and precision. The results suggest that protocol details such as cell line ID, media exchange, cell handling, and nanoparticle dispersion are critical to ensure protocol robustness and comparability of nanocytotoxicity assay results. The combination of system control measurements and interlaboratory comparison data yielded insights that would not have been available by either approach by itself.

Silver nanoparticles (AgNPs) are widely used in industry, consumer products, and medical appliances due to their efficient antimicrobial properties. However, information on environmental toxicity and bacterial impact of these particles is not completely elucidated. Results showed that AgNPs produced growth inhibition and oxidative stress in bacteria Escherichia coli (gram negative) and Staphylococcus aureus (gram positive), with half-maximal inhibitory concentrations (IC) of 12 and 7 mg/L, respectively. Surprisingly, bacteria pre-exposed to sublethal dose of AgNPs exhibited increased resistance toward antibiotics (ampicillin and Pen-Strep) with IC elevated by 3-13-fold. Further, AgNP pre-exposure raised the minimal inhibitory concentration and minimal biocidal concentration by two- to eightfold when cells were challenged with antibiotics with diverse mechanisms of action (penicillin, chloramphenicol, and kanamycin). Interestingly, we found that upon exposure to ampicillin, strains pretreated with AgNPs exhibited lower levels of membrane damage and oxidative stress, together with elevated levels of intracellular ATP relative to untreated cells. Bacterial reverse mutation assay (Ames test) showed that AgNPs are highly mutagenic, consistent with further assays demonstrating abiotic reactive oxygen species (ROS) generation and intrinsic DNA cleavage activity in vitro of AgNPs. Overall, our results suggest that AgNPs enhance bacterial resistance to antibiotics by promoting stress tolerance through induction of intracellular ROS. Our data suggest potential consequences of incidental environmental exposure of bacteria to AgNPs and indicate the need to regulate use and disposal of AgNPs in industry and consumer products.

Silver nanoparticles (AgNPs) are increasingly used in various products and consequentially the potential adverse effects associated with exposure to them are of concern. This study investigated the effects of AgNPs on the hepatic drug-metabolizing enzymes of the cytochrome P450 (CYP) families 1, 2 and 3, using both in vitro and in vivo biological assays. AgNPs were orally administered to Sprague-Dawley rats at various concentrations (0-1000 mg/kg body weight/day) for 2 weeks. No effect was found on the plasma levels of ALT, AST and ALP in all treated rat groups, and no significant change in the activities of CYP1A, CYP2C, CYP2D, CYP2E1 and CYP3A was observed for all tested AgNP doses. The results correlated with the observation that no AgNPs were detected in the liver sections of the tested rats. However, the in vitro system using rat liver microsomes demonstrated a strong inhibition of CYP2C (IC(50) = 28 µg/mL) and CYP2D (IC(50) = 23 µg/mL) activities, but not of CYP1A, CYP2E1 and CYP3A activities (IC(50) > 100 µg/mL) at concentrations up to 100 µg/mL of AgNPs. The inhibitory effect of AgNPs on these CYPs indicates the possibility of the AgNP-drug interaction when co-administered with some medicines and this may cause adverse effects to patients.

Troglitazone (TRO), an effective thiazolidinedione antidiabetic agent, was reported to produce idiosyncratic hepatotoxic effects in some individuals. In contrast, rosiglitazone (RSG), in the same group of agents, has no significant toxic effects and now is widely used. In this study, human hepatoma (HepG2) cell lines were exposed to various doses of TRO as well as RSG (0, 25, 50, and 75 microM) for 48 h. Cell lysates were separated by two-dimensional electrophoresis, and the gels were stained with coomassie brilliant blue to compare the spot profiles. The greatest protein expression at a MW of 75 kDa and isoelectric point of 5 was specifically increased with TRO treatments of 50 and 75 microM. The spot was identified as a mixture of immunoglobulin heavy chain binding protein (BiP) and, to a lesser extent, protein disulfide isomerase-related protein (PDIrp). Immunoblot analyses showed that the BiP protein was dose-dependently increased by TRO treatment and, to a lower degree, by RSG. These effects were also correlated with the high induction of BiP mRNA by TRO (50 and 75 microM) and the lower induction by RSG. However, both treatments showed no significant effects on PDIrp expression. The toxic effects of TRO in relation to the overexpression of BiP were also demonstrated in HLE cells, another human hepatoma cell line. In HLE cells, the inhibition of BiP expression by small interference RNA rendered cells more susceptible to the toxic effects of TRO. These results suggest that the overexpression of BiP is a defense mechanism of the endoplasmic reticulum in response to TRO-induced toxicity.

Cytochrome P450 (CYP) enzymes are responsible for oxidative metabolisms of a large number of xenobiotics. In this study, we investigated interactions of silver nanoparticles (AgNPs) and silver ions (Ag+) with six CYP isoforms, namely, CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4, within CYP-specific inhibitor-binding pockets by molecular docking and quantum mechanical (QM) calculations. The docking results revealed that the Ag3 cluster, not Ag+, interacted with key amino acids of CYP2C9, CYP2C19, and CYP2D6 within a distance of about 3 Å. Moreover, the QM analysis confirmed that the amino acid residues of these CYP enzymes strongly interacted with the Ag3 cluster, providing more insight into the mechanism of the potential inhibition of CYP enzyme activities. Interestingly, these results are consistent with previous in vitro data indicating that AgNPs inhibited activities of CYP2C and CYP2D in rat liver microsomes. It is suggested that the Ag3 cluster is a minimal unit of AgNPs for in silico modeling. In summary, we demonstrated that molecular docking, together with QM analysis, is a promising tool to predict AgNP-mediated CYP inhibition. These methods are useful for deeper understanding of reaction mechanisms and could be used for other nanomaterials.