Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface

Amino acid mediated synthesis of silver nanoparticles and preparation of antimicrobial agar/silver nanoparticles composite films

Silver nanoparticles (AgNPs) were synthesized using amino acids (tyrosine and tryptophan) as reducing and capping agents, and they were incorporated into the agar to prepare antimicrobial composite films. The AgNPs solutions exhibited characteristic absorption peak at 420 nm that showed a red shift to ∼434 nm after forming composite with agar. XRD data demonstrated the crystalline structure of AgNPs with dominant (111) facet. Apparent surface color and transmittance of agar films were greatly influenced by the AgNPs. The incorporation of AgNPs into agar did not exhibit any change in chemical structure, thermal stability, moisture content, and water vapor permeability. The water contact angle, tensile strength, and modulus decreased slightly, but elongation at break increased after AgNPs incorporation. The agar/AgNPs nanocomposite films possessed strong antibacterial activity against Listeria monocytogenes and Escherichia coli. The agar/AgNPs film could be applied to the active food packaging by controlling the food-borne pathogens.

Bacteriagenic silver nanoparticles: synthesis, mechanism, and applications

Silver nanoparticles (AgNPs) have received tremendous attention due to their significant antimicrobial properties. Large numbers of reports are available on the physical, chemical, and biological syntheses of colloidal AgNPs. Since there is a great need to develop ecofriendly and sustainable methods, biological systems like bacteria, fungi, and plants are being employed to synthesize these nanoparticles. The present review focuses specifically on bacteria-mediated synthesis of AgNPs, its mechanism, and applications. Bacterial synthesis of extra- and intracellular AgNPs has been reported using biomass, supernatant, cell-free extract, and derived components. The extracellular mode of synthesis is preferred over the intracellular mode owing to easy recovery of nanoparticles. Silver-resistant genes, c-type cytochromes, peptides, cellular enzymes like nitrate reductase, and reducing cofactors play significant roles in AgNP synthesis in bacteria. Organic materials released by bacteria act as natural capping and stabilizing agents for AgNPs, thereby preventing their aggregation and providing stability for a longer time. Regulation over reaction conditions has been suggested to control the morphology, dispersion, and yield of nanoparticles. Bacterial AgNPs have anticancer and antioxidant properties. Moreover, the antimicrobial activity of AgNPs in combination with antibiotics signifies their importance in combating the multidrug-resistant pathogenic microorganisms. Multiple microbicidal mechanisms exhibited by AgNPs, depending upon their size and shape, make them very promising as novel nanoantibiotics.

Surface enhanced Raman scattering of amino acids assisted by gold nanoparticles and Gd(3+) ions

The surface enhanced raman scattering (SERS) signal from the l-tyrosine (tyr) molecule adsorbed on gold nanoparticles (Au-tyr) is compared with the SERS signal assisted by the presence of gadolinium ions (Gd(3+)) coordinated with the Au-tyr system. An enhancement factor of the SERS signal in the presence of Gd(3+) ions was ∼5 times higher than that produced by l-tyrosine adsorbed on gold nanoparticles. The enhancement of the SERS signal can be attributed to a corresponding increase in the local electric field due to the presence of Gd(3+) ions in the vicinity of a gold dimer configuration. This scenario was confirmed by solving numerically Maxwell equations, showing an increase of 1 order of magnitude in the local electric scattered field when the Gd(3+) ion is located in between a gold dimer compared with naked gold nanoparticles.

Bio-synthesis of silver nanoparticles using Potentilla fulgens Wall. ex Hook. and its therapeutic evaluation as anticancer and antimicrobial agent

The present study aims to develop an easy and eco-friendly method for the synthesis of silver nanoparticles using extracts from the medicinal plant, Potentilla fulgens and evaluation of its anticancer and antimicrobial properties. The various parts of P. fulgens were screened and the root extract was found to have the highest potential for the synthesis of nanoparticles. The root extracts were able to quickly reduce Ag(+) to Ag(0) and stabilized the nanoparticles. The synthesis of nanoparticles was confirmed by UV-Visible spectrophotometry and further characterized using Zeta sizer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Electron microscopic study showed that the size of the nanoparticle was in the range of 10 to 15 nm and spherical in shape. The studies of phytochemical analysis of nanoparticles indicated that the adsorbed components on the surface of nanoparticles were mainly flavonoid in nature. Furthermore, nanoparticles were evaluated as cytotoxic against various cancer cell lines and 0.2 to 12 μg/mL nanoparticles showed good toxicity. The IC50 value of nanoparticles was found to be 4.91 and 8.23 μg/mL against MCF-7 and U-87 cell lines, respectively. Additionally, the apoptotic effect of synthesized nanoparticles on normal and cancer cells was studied using trypan blue assay and flow-cytometric analysis. The results indicate the synthesized nanoparticle ability to kill cancer cells compared to normal cells. The nanoparticles also exhibited comparable antimicrobial activity against both Gram-positive and Gram-negative bacteria.

Imine (–CHN–) brings selectivity for silver enhanced fluorescence

Strong silver and gold stimulated fluorescence enhancement of alkaline salicylaldehyde solution have been observed. Ammonia or primary amine quantitatively eliminates gold enhanced fluorescence, keeping silver enhanced fluorescence unaffected.

A tyrosine-rich peptide induced flower-like palladium nanostructure and its catalytic activity

​Flower-like palladium nanostructure (Pd nano-flower) induced by tyrosine-rich peptide, Tyr-Tyr-Ala-His-Ala-Tyr-Tyr (YYAHAYY), showed excellent catalytic activities in copper-free Sonogashira cross-coupling reaction in water.

Fabrication of gold nanoparticles on biotin-di-tryptophan scaffold for plausible biomedical applications

AuNPs were synthesized and encapsulated by spherical scaffold of biotinylated di-tryptophan and such devices can be used for plausible biomedical applications.

New insights into the formation mechanism of Ag, Au and AgAu nanoparticles in aqueous alkaline media: alkoxides from alcohols, aldehydes and ketones as universal reducing agents

Alkoxide from alcohols, aldehydes and ketones in alkaline medium is the actual and universal reducing agent of silver and gold ions.

Kinetically controlled nucleation of silver on surfactant-free gold seeds

We report on the heterogeneous nucleation of Ag on Au seeds using a surfactant-free synthesis where nanoparticle aggregation is nullified through the immobilization of bare Au seeds on the surface of a substrate. Requiring only silver nitrate, ascorbic acid, and Au seeds, the synthesis is facile and, from a mechanistic standpoint, far less convoluted than conventional protocols. The results reveal that, even in the absence of surfactants, highly anisotropic growth modes are achieved which result in a lone Ag structure emanating from a single (100) Au facet. Consistent with surfactant-based protocols is the ability to vary the product of the reaction by varying the reaction rate. It allows for kinetic control which is able to direct the reaction toward either a bimetallic heterodimer or a core-shell configuration. The observed growth modes cannot be explained in terms of those proposed for surfactant-based growth modes where surfactants, surface diffusion, and/or collision patterns are used to rationalize the reaction product. We, instead, propose a growth mode reliant on the formation of a space charge region around each seed consisting of a double layer of ions, where the integrity of the layer is dependent upon the facets expressed by the seed, the rate at which the reduced ions are being deposited, and the pH of the solution. Our work reveals the rich nature of surfactant-free heteroepitaxial growth modes as well as the utility of the substrate-based platform in defining growth pathways.

DNase 1 retains endodeoxyribonuclease activity following gold nanocluster synthesis

Here we present the synthesis of the enzyme DNase 1 stabilized gold nanoclusters (DNase 1:AuNCs) with core size consisting of either 8 or 25 atoms. The DNase 1:Au8NCs exhibit blue fluorescence whereas the DNase 1:Au25NCs are red emitting. In addition to the intense fluorescence emission, the synthesized DNase 1:AuNC hybrid retains the native functionality of the protein, allowing simultaneous detection and digestion of DNA with a detection limit of 2 μg/mL. The DNase 1:AuNCs could be conveniently employed as efficient and fast sensors to augment the current time-consuming DNA contamination analysis techniques.

Microbial synthesis of gold nanoparticles: current status and future prospects

Gold nanoparticles have been employed in biomedicine since the last decade because of their unique optical, electrical and photothermal properties. Present review discusses the microbial synthesis, properties and biomedical applications of gold nanoparticles. Different microbial synthesis strategies used so far for obtaining better yield and stability have been described. It also includes different methods used for the characterization and analysis of gold nanoparticles, viz. UV-visible spectroscopy, Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, scanning electron microscopy, ransmission electron microscopy, atomic force microscopy, electron dispersive X ray, X ray photoelectron spectroscopy and cyclic voltametry. The different mechanisms involved in microbial synthesis of gold nanoparticles have been discussed. The information related to applications of microbially synthesized gold nanoparticles and patents on microbial synthesis of gold nanoparticles has been summarized.

Plant extract: a promising biomatrix for ecofriendly, controlled synthesis of silver nanoparticles

Uses of plants extracts are found to be more advantageous over chemical, physical and microbial (bacterial, fungal, algal) methods for silver nanoparticles (AgNPs) synthesis. In phytonanosynthesis, biochemical diversity of plant extract, non-pathogenicity, low cost and flexibility in reaction parameters are accounted for high rate of AgNPs production with different shape, size and applications. At the same time, care has to be taken to select suitable phytofactory for AgNPs synthesis based on certain parameters such as easy availability, large-scale nanosynthesis potential and non-toxic nature of plant extract. This review focuses on synthesis of AgNPs with particular emphasis on biological synthesis using plant extracts. Some points have been given on selection of plant extract for AgNPs synthesis and case studies on AgNPs synthesis using different plant extracts. Reaction parameters contributing to higher yield of nanoparticles are presented here. Synthesis mechanisms and overview of present and future applications of plant-extract-synthesized AgNPs are also discussed here. Limitations associated with use of AgNPs are summarised in the present review.

Silver Nanoparticle Synthesis Using Monosaccharides and Their Growth Inhibitory Activity against Gram-Negative and Positive Bacteria

Using various monosaccharides as reductant, we synthesized Ag nanoparticles (NPs) in seconds employing the household microwave method described earlier. The Ag NPs containing colloidal solution showed distinctive colors with varying λmax. The sizes of the NPs formed varied significantly from 10 to 35 nm in good agreement with the localized plasmon resonance ranged from ~300 to ~600 nm. The antimicrobial properties of these NPs were compared in Gram-negative and positive bacteria in liquid culture. Gram-positive bacteria were highly susceptible compared to Gram-negative microbes—the additional lipopolysaccharide layer covering the peptidoglycan cell wall in the latter somewhat lessens the effect. The results indicated that larger NPs produced by glucose inhibited bacterial growth better than the smallest NPs produced by ribose. This may be attributed to the higher aggregation rate for larger NPs on cell wall. SEM analysis showed accumulation of NPs on cell surface and defect in budding, further supporting the cell wall interaction with Ag NPs. These observations suggested that the growth inhibition of Ag NPs is mediated by interfering with the bacterial cell wall peptidoglycan.

Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates

The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed.

Synthesis of fluorescent metal nanoparticles in aqueous solution by photochemical reduction

A facile green chemistry approach for the synthesis of sub-5 nm silver and gold nanoparticles is reported. The synthesis was achieved by a photochemical method using tyrosine as the photoreducing agent. The size of the gold and silver nanoparticles was about 3 and 4 nm, respectively. The nanoparticles were characterized using x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy. Both silver and gold nanoparticles synthesized by this method exhibited fluorescence properties and their use for cell imaging applications has been demonstrated.

Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles

We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPs(Y)) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.

Synthesis and characterization of biocompatible gymnemic acid–gold nanoparticles: a study on glucose uptake stimulatory effect in 3T3-L1 adipocytes

An enhancedin vitroglucose utilization action of the biosynthesized GA–AuNPs.

Label-free detection of C-reactive protein using highly dispersible gold nanoparticles synthesized by reducible biomimetic block copolymers

The label-free detection of CRP as an infection biomarker was successfully demonstrated by using the biomimetic block copolymer-protected gold nanoparticles.

A facile synthesis of flower-shaped TiO2/Ag microspheres and their application in photocatalysts

Novel flower-shaped microspheres (FSMP) TiO₂/Ag nanoparticles composites were fabricated by the facile tyrosine-reduced method and used as a photocatalyst for the degradation of MB under light irradiation. The results indicate that as-prepared composite microspheres have a superior photocatalytic activity attributed to higher surface area, increased light absorption capability, the reduction of electron–hole pair recombination.

Fine-tuning the antimicrobial profile of biocompatible gold nanoparticles by sequential surface functionalization using polyoxometalates and lysine

Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPs(Tyr)) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona.

REVIEW OF METAL, CARBON AND POLYMER NANOPARTICLES FOR INFRARED PHOTOTHERMAL THERAPY

The aim of this review is to provide an up-to-date overview of nanoparticles developed for use as photothermal therapy agents (PTT) over the past five years. The main emphasis is on nanoparticles that absorb near infrared (NIR) light for PTT of cancer. Mild hyperthermia, including drug delivery, versus thermal ablation is also discussed. Recent advances in the synthesis of highly anisotropic novel metal nanoparticles for PTT are described. New metals and metal oxide complexes, as well as the use of quantum dots for PTT and as imaging agents are newer areas of development that are explained. This review also highlights current progress in the development of carbon nanoparticles, including reduced graphene oxide for both thermal ablation as well as drug delivery. The review culminates in the recent use electrically conductive polymer nanoparticles for hyperthermia. The advantages and unique features of these contemporary nanoparticles being used for PTT are highlighted. The goal of the present work is to describe the recent evolution of nanoparticles for NIR stimulated PTT, and highlight the innovations and future directions.

Versatile photochemical surface modification of biopolyester microfibrous scaffolds with photogenerated silver nanoparticles for antibacterial activity

A straightforward and versatile method for immobilizing macromolecules and silver nanoparticles on the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) electrospun fibers is developed with the objective of designing a new functional material having significant antibacterial activity. The approach relies on a two-step procedure: UV photografting of poly(methacrylic acid) (PMAA) on the surface of PHBHV fibers according to a "grafting from" method, and complexation of in situ photogenerated silver nanoparticles (Ag NPs) by carboxyl groups from tethered PMAA chains. The photografting process is conducted through a photoinduced free-radical process employing a ketone-based photoinitiator in aqueous medium. Under appropriate conditions, the photogenerated radicals abstract hydrogen atoms from the PHBHV backbone, thus initiating the UV-mediated photopolymerization of MAA from the PHBHV microfibrous surface. The photochemical mechanism of the ketone photolysis is entirely described by the electron spin resonance/spin-trapping technique, and the modified PHBHV microfibrous scaffold is extensively characterized by ATR-FTIR spectroscopy, water contact-angle measurements, and mercury intrusion porosimetry. In a second step, the in situ synthesis of Ag NPs within the microfibrous scaffold is implemented by photoreduction reaction in the presence of both a silver precursor and a photosensitizer. The photoinduced formation of Ag NPs is confirmed by UV spectrophotometry and XPS analysis. SEM and TEM experiments confirm the formation and dispersion of Ag NPs on the surface of the modified fibers. Finally, a primary investigation is conducted to support the antibacterial activity of the new functionalized biomaterial against Staphylococcus aureus and Escherichia coli.

Highly selective and sensitive detection of coralyne based on the binding chemistry of aptamer and graphene oxide

In this contribution, an organic small molecule (OSM)-participating interaction between its aptamer and graphene oxide (GO) is investigated by taking coralyne as an example. Based on their interactions, a simple, rapid, highly sensitive and selective fluorometric method for the detection of coralyne is developed. GO can effectively quench the fluorescence of dye-labeled aptamer, while stronger binding of the aptamer and its target can make the fluorescence be recovered, which have been well demonstrated by the studies of the fluorescence spectra, fluorescence anisotropy, and circular dichroism spectra. In this case, the coralyne can be quantificationally detected by the variation of the fluorescence intensity, where GO acts as an efficient signal-to-background enhancer. With the increase of the coralyne, the fluorescence intensity increases gradually and linearly proportional to the concentration of the coralyne in the range of 10-700 nmol L(-1). This method is reliable, and has been successfully applied for the detection of coralyne in complicated matrixes.

One-pot, green, rapid synthesis of flowerlike gold nanoparticles/reduced graphene oxide composite with regenerated silk fibroin as efficient oxygen reduction electrocatalysts

Flowerlike gold nanoparticles (Au NPs)/reduced graphene oxide (RGO) composites were fabricated by a facile, one-pot, environmentally friendly method in the presence of regenerated silk fibroin (RSF). The influences of reaction time, temperature, and HAuCl(4): RGO ratio on the morphology of Au NPs loaded on RGO sheets were discussed and a tentative mechanism for the formation of flowerlike Au NPs/RGO composite was proposed. In addition, the flowerlike Au NPs/RGO composite showed superior catalytic performance for oxygen reduction reaction (ORR) to Au/RGO composites with other morphologies. Our work provides an alternative facile and green approach to synthesize functional metal/RGO composites.

Retracted Article: Aqueous synthesis of human serum albumin-stabilized fluorescent Au/Ag core/shell nanocrystals for highly sensitive and selective sensing of copper(ii)

Using human serum albumin as a reductive plus stabilizing agent, fluorescent Au/Ag core/shell nanocrystals were prepared at pH 9.0 and 37 °C, and further developed as a highly sensitive and selective sensor of Cu²⁺.

Enzyme mimics of Au/Ag nanoparticles for fluorescent detection of acetylcholine

We have developed a highly sensitive and selective fluorescent assay for the detection of acetylcholine (ACh) based on enzyme mimics of Au/Ag nanoparticles (NPs). These NPs were prepared via a one-step solution phase reaction between 13 nm Au NPs and Ag(+) ions in the presence of stabilizing agents such as adenosine triphosphate (ATP) and polyethylene glycol (PEG). Our sensing strategy involves reacting ACh with acetylcholinesterase (AChE) to form choline that is in turn oxidized by choline oxidase (ChOx) to produce betaine and H(2)O(2), which reacts with Amplex UltraRed (AUR) in the presence of bimetallic NPs catalyst to form a fluorescent product. The fluorescence intensity (excitation/emission wavelengths of 540/592 nm) is proportional to the concentration of ACh over a range of 1-100 nM (R(2) = 0.998), with a limit of detection of 0.21 nM (signal/noise = 3). When compared with Au NPs and horseradish peroxidase, the Au/Ag NPs provide 150- and 115-fold higher catalytic activity toward the H(2)O(2)-mediated AUR reaction. The practicality of the assay has been validated by determining the concentrations of ACh in plasma and blood samples, with results of 2.69 ± 0.84 nM (n = 5) and 6.75 ± 1.42 nM (n = 5), respectively. Thus, the present assay holds great potential for the analysis of ACh in biological samples.

Designed plasmonic nanocatalysts for the reduction of eosin Y: absorption and fluorescence study

In this work, we report a one-step green synthesis of gold nanoparticles (AuNPs) by microwave irradiation using nontoxic and biodegradable polysaccharide chitosan as a reducing and stabilizing agent. The interaction between gold nanoparticles with the amine group of chitosan was confirmed by Fourier transform infrared spectroscopy analysis, and the stability of the nanoparticle is ascertained by zeta potential measurements. Transmission electron microscopy photograph and dynamic light scattering measurements confirmed the average size of gold nanoparticles as 25 nm. The ability of the synthesised gold nanoparticles as a catalyst for the reduction of eosin dye in the presence of NaBH4 was monitored by means of spectrofluorometry and spectrophotometry. It is found that the NaBH4-induced reduction of eosin is enhanced in the presence of AuNPs even without a catalyst. Time-resolved fluorescence decay studies also confirmed the reduction of eosin in the presence of AuNPs.

Exposure to silver nanoparticles inhibits selenoprotein synthesis and the activity of thioredoxin reductase

BACKGROUND

Silver nanoparticles (AgNPs) and silver (Ag)-based materials are increasingly being incorporated into consumer products, and although humans have been exposed to colloidal Ag in many forms for decades, this rise in the use of Ag materials has spurred interest into their toxicology. Recent reports have shown that exposure to AgNPs or Ag ions leads to oxidative stress, endoplasmic reticulum stress, and reduced cell proliferation. Previous studies have shown that Ag accumulates in tissues as silver sulfides (Ag2S) and silver selenide (Ag2Se).

OBJECTIVES

In this study we investigated whether exposure of cells in culture to AgNPs or Ag ions at subtoxic doses would alter the effective metabolism of selenium, that is, the incorporation of selenium into selenoproteins.

METHODS

For these studies we used a keratinocyte cell model (HaCat) and a lung cell model (A549). We also tested (in vitro, both cellular and chemical) whether Ag ions could inhibit the activity of a key selenoenzyme, thioredoxin reductase (TrxR).

RESULTS

We found that exposure to AgNPs or far lower levels of Ag ions led to a dose-dependent inhibition of selenium metabolism in both cell models. The synthesis of protein was not altered under these conditions. Exposure to nanomolar levels of Ag ions effectively blocked selenium metabolism, suggesting that Ag ion leaching was likely the mechanism underlying observed changes during AgNP exposure. Exposure likewise inhibited TrxR activity in cultured cells, and Ag ions were potent inhibitors of purified rat TrxR isoform 1 (cytosolic) (TrxR1) enzyme.

CONCLUSIONS

Exposure to AgNPs leads to the inhibition of selenoprotein synthesis and inhibition of TrxR1. Further, we propose these two sites of action comprise the likely mechanism underlying increases in oxidative stress, increases endoplasmic reticulum stress, and reduced cell proliferation during exposure to Ag.