Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity
Title: Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity
The fish intestine is an important barrier for environmental toxicants, including metals and metal nanoparticles. Tracking chemical transformation at the interface between the intestinal epithelium and the intestinal lumen can inform us about chemicals' bio-reactivity and toxicity but is challenging due to the lack of appropriate models. To allow for such investigations, a model of the fish intestine derived from rainbow trout ( Oncorhynchus mykiss ), the RTgutGC cell line, was used. Cells were exposed to silver nitrate (AgNO 3 ) or citrate coated silver nanoparticles (cit-AgNPs) in Leibovitz's L-15 medium without amino acids and vitamins (L-15/ex), which allowed the determination of the extracellular silver species using a chemical equilibrium model. X-ray absorption spectroscopy (XAS) was used to track intracellular silver speciation. Cellular toxicity, silver accumulation, and metallothionein (MT) mRNA levels were also measured. Cells accumulated the same concentrations of silver when exposed to equimolar amounts ( i.e. 1, 5 and 10 μM) of AgNO 3 or cit-AgNPs. However, AgNO 3 was shown to be more toxic than cit-AgNPs. Intracellular silver speciation changed over time in both exposure series. After 1 hour, intracellular silver speciation was dominated by chloride complexation in both exposures. After 24 and 72 hours of exposure to cit-AgNPs, ∼7% of silver was complexed to cysteine, whereas the remaining silver was AgNPs. In cells exposed to AgNO 3 for 72 hours, 97% of Ag was complexed to cysteine. A significant increase, compared to controls, in metallothionein mRNA levels at 24 and 72 hours of exposure to AgNO 3 and cit-AgNPs can explain the formation of Ag–cysteine complexes. In summary, these data show that silver chloride species are bioavailable and that complexation to cysteine scavenges intracellular dissolved silver ions, thus preventing toxicity. Silver nanoparticles present a similar but attenuated toxic response to AgNO 3 . Thus, at least in acute exposures, existing risk assessment for dissolved silver species could be protective for nanosilver. more »« less
Arek M. Engstrom, Henry Wu(
, International journal of engineering research and applications)
null
(Ed.)
Silver nanoparticles (AgNPs) are widely used in various commercial and industrial applicationsbecause of their antimicrobial properties.The behavior and toxicity of AgNPs are likely controlled by physicochemical properties such as size, shape, and surface chemistry; however, studies of these properties are often confounded by Ag+ ion dissolution. Here a suite of spherical and triangular shaped AgNPs were prepared with increasing amounts of surface protection from their surface-coating comprising of citrate (Cit) only or a mixture
Cunningham, Brittany; Engstrom, Arek M.; Harper, Bryan J.; Harper, Stacey L.; Mackiewicz, Marilyn R.(
, Nanomaterials)
null
(Ed.)
Silver nanoparticles (AgNPs) are widely used in commerce, however, the effect of their physicochemical properties on toxicity remains debatable because of the confounding presence of Ag+ ions. Thus, we designed a series of AgNPs that are stable to surface oxidation and Ag+ ion release. AgNPs were coated with a hybrid lipid membrane comprised of L-phosphatidylcholine (PC), sodium oleate (SOA), and a stoichiometric amount of hexanethiol (HT) to produce oxidant-resistant AgNPs, Ag–SOA–PC–HT. The stability of 7-month aged, 20–100 nm Ag–SOA–PC–HT NPs were assessed using UV–Vis, dynamic light scattering (DLS), and inductively coupled plasma mass spectrometry (ICP-MS), while the toxicity of the nanomaterials was assessed using a well-established, 5-day embryonic zebrafish assay at concentrations ranging from 0–12 mg/L. There was no change in the size of the AgNPs from freshly made samples or 7-month aged samples and minimal Ag+ ion release (<0.2%) in fishwater (FW) up to seven days. Toxicity studies revealed AgNP size- and concentration-dependent effects. Increased mortality and sublethal morphological abnormalities were observed at higher concentrations with smaller nanoparticle sizes. This study, for the first time, determined the effect of AgNP size on toxicity in the absence of Ag+ ions as a confounding variable.
Miesen, Thomas J.; Engstrom, Arek M.; Frost, Dane C.; Ajjarapu, Ramya; Ajjarapu, Rohan; Lira, Citlali Nieves; Mackiewicz, Marilyn R.(
, RSC Advances)
null
(Ed.)
The controlled synthesis of stable silver nanoparticles (AgNPs), that do not undergo surface oxidation and Ag + ion dissolution, continues to be a major challenge. Here the synthesis of robust hybrid lipid-coated AgNPs, comprised of l -α-phosphatidylcholine (PC) membranes anchored by a stoichiometric amount of long-chained hydrophobic thiols and sodium oleate (SOA) as hydrophobic binding partners, that do not undergo surface oxidation and Ag + ion dissolution, is described. UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometry (ICP-MS) demonstrate that in the presence of strong oxidants, such as potassium cyanide (KCN), the hybrid lipid-coated AgNPs are stable and do not undergo surface oxidation even in the presence of membrane destabilizing surfactants. UV-Vis studies show that the stability of hybrid lipid-coated AgNPs of various sizes and shapes is dependent on the length of the thiol hydrocarbon chain and can be ranked in the order of increasing stability as follows: propanethiol (PT) < hexanethiol (HT) ≤ decanethiol (DT). UV-Vis and ICP-MS studies show that the hybrid lipid-coated AgNPs do not change in size or shape confirming that the AgNPs do not undergo surface oxidation and Ag + ion dissolution when placed in the presence of strong oxidants, chlorides, thiols, and low pH. Long-term stability studies, over 21 days, show that the hybrid lipid-coated AgNPs do not release Ag + ions and are more stable. Overall, these studies demonstrate hybrid membrane encapsulation of nanomaterials is a viable method for stabilizing AgNPs in a “shape-locked” form that is unable to undergo surface oxidation, Ag + ion release, aging, or shape conversion. More importantly, this design strategy is a simple approach to the synthesis and stabilization of AgNPs for a variety of biomedical and commercial applications where Ag + ion release and toxicity is a concern. With robust and shielded AgNPs, investigators can now evaluate and correlate how the physical features of AgNPs influence toxicity without the confounding factor of Ag + ions present in samples. This design strategy also provides an opportunity where the membrane composition can be tuned to control the release rate of Ag + ions for optimizing antimicrobial activity.
Silver nanoparticles (AgNPs) are one of the most used engineered nanomaterials. Despite progress in assessing their environmental implications, knowledge gaps exist concerning the metabolic perturbations induced by AgNPs on phytoplankton, essential organisms in global biogeochemical cycles and food-web dynamics. We combine targeted metabolomics, biouptake and physiological response studies to elucidate metabolic perturbations in algaPoterioochromonas malhamensisinduced by AgNPs and dissolved Ag. We show time-dependent perturbation of the metabolism of amino acids, nucleotides, fatty acids, tricarboxylic acids, photosynthesis and photorespiration by both Ag-treatments. The results suggest that dissolved Ag ions released by AgNPs are the major toxicity driver; however, AgNPs internalized in food vacuoles contributed to the perturbation of amino acid metabolism, TCA cycle and oxidative stress. The metabolic perturbations corroborate the observed physiological responses. We highlight the potential of metabolomics as a tool for understanding the molecular basis for these metabolic and physiological changes, and for early detection of stress.
Xu, Chi; Andaraarachchi, Himashi P; Xiong, Zichang; Eslamisaray, Mohammad Ali; Kushner, Mark J; Kortshagen, Uwe R(
, Journal of Physics D: Applied Physics)
Abstract Silver nanoparticles (NPs) are extensively used in electronic components, chemical sensors, and disinfection applications, in which many of their properties depend on particle size. However, control over silver NP size and morphology still remains a challenge for many synthesis techniques. In this work, we demonstrate the surfactant-free synthesis of silver NPs using a low-pressure inductively coupled nonthermal argon plasma. Continuously forming droplets of silver nitrate (AgNO 3 ) precursor dissolved in glycerol are exposed to the plasma, with the droplet residence time being determined by the precursor flow rate. Glycerol has rarely been studied in plasma-liquid interactions but shows favorable properties for controlled NP synthesis at low pressure. We show that the droplet residence time and plasma power have strong influence on NP properties, and that improved size control and particle monodispersity can be achieved by pulsed power operation. Silver NPs had mean diameters of 20 nm with geometric standard deviations of 1.6 under continuous wave operation, which decreased to 6 nm mean and 1.3 geometric standard deviation for pulsed power operation at 100 Hz and 20% duty cycle. We propose that solvated electrons from the plasma and vacuum ultraviolet (VUV) radiation induced electrons produced in glycerol are the main reducing agents of Ag + , the precursor for NPs, while no significant change of chemical composition of the glycerol solvent was detected.
Minghetti, Matteo, Dudefoi, William, Ma, Qing, and Catalano, Jeffrey G. Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity. Retrieved from https://par.nsf.gov/biblio/10167397. Environmental Science: Nano 6.10 Web. doi:10.1039/c9en00710e.
Minghetti, Matteo, Dudefoi, William, Ma, Qing, & Catalano, Jeffrey G. Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity. Environmental Science: Nano, 6 (10). Retrieved from https://par.nsf.gov/biblio/10167397. https://doi.org/10.1039/c9en00710e
Minghetti, Matteo, Dudefoi, William, Ma, Qing, and Catalano, Jeffrey G.
"Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity". Environmental Science: Nano 6 (10). Country unknown/Code not available. https://doi.org/10.1039/c9en00710e.https://par.nsf.gov/biblio/10167397.
@article{osti_10167397,
place = {Country unknown/Code not available},
title = {Emerging investigator series: linking chemical transformations of silver and silver nanoparticles in the extracellular and intracellular environments to their bio-reactivity},
url = {https://par.nsf.gov/biblio/10167397},
DOI = {10.1039/c9en00710e},
abstractNote = {The fish intestine is an important barrier for environmental toxicants, including metals and metal nanoparticles. Tracking chemical transformation at the interface between the intestinal epithelium and the intestinal lumen can inform us about chemicals' bio-reactivity and toxicity but is challenging due to the lack of appropriate models. To allow for such investigations, a model of the fish intestine derived from rainbow trout ( Oncorhynchus mykiss ), the RTgutGC cell line, was used. Cells were exposed to silver nitrate (AgNO 3 ) or citrate coated silver nanoparticles (cit-AgNPs) in Leibovitz's L-15 medium without amino acids and vitamins (L-15/ex), which allowed the determination of the extracellular silver species using a chemical equilibrium model. X-ray absorption spectroscopy (XAS) was used to track intracellular silver speciation. Cellular toxicity, silver accumulation, and metallothionein (MT) mRNA levels were also measured. Cells accumulated the same concentrations of silver when exposed to equimolar amounts ( i.e. 1, 5 and 10 μM) of AgNO 3 or cit-AgNPs. However, AgNO 3 was shown to be more toxic than cit-AgNPs. Intracellular silver speciation changed over time in both exposure series. After 1 hour, intracellular silver speciation was dominated by chloride complexation in both exposures. After 24 and 72 hours of exposure to cit-AgNPs, ∼7% of silver was complexed to cysteine, whereas the remaining silver was AgNPs. In cells exposed to AgNO 3 for 72 hours, 97% of Ag was complexed to cysteine. A significant increase, compared to controls, in metallothionein mRNA levels at 24 and 72 hours of exposure to AgNO 3 and cit-AgNPs can explain the formation of Ag–cysteine complexes. In summary, these data show that silver chloride species are bioavailable and that complexation to cysteine scavenges intracellular dissolved silver ions, thus preventing toxicity. Silver nanoparticles present a similar but attenuated toxic response to AgNO 3 . Thus, at least in acute exposures, existing risk assessment for dissolved silver species could be protective for nanosilver.},
journal = {Environmental Science: Nano},
volume = {6},
number = {10},
author = {Minghetti, Matteo and Dudefoi, William and Ma, Qing and Catalano, Jeffrey G.},
}
Warning: Leaving National Science Foundation Website
You are now leaving the National Science Foundation website to go to a non-government website.
Website:
NSF takes no responsibility for and exercises no control over the views expressed or the accuracy of
the information contained on this site. Also be aware that NSF's privacy policy does not apply to this site.
