Stability of Citrate, PVP, and PEG Coated Silver Nanoparticles in Ecotoxicology Media

Abstract

Silver nanoparticles (AgNPs) are present in the environment and a number of ecotoxicology studies have shown that AgNPs might be highly toxic. Nevertheless, there are little data on their stability in toxicology media. This is an important issue as such dynamic changes affect exposure dose and the nature of the toxicant studied and have a direct impact on all (eco)toxicology data. In this study, monodisperse citrate, PVP, and PEG coated AgNPs with a core size of approximately 10 nm were synthesized and characterized; their behavior was examined in standard OECD media used for Daphnia sp. acute and chronic tests (in the absence of Daphnia). Surface plasmon resonance, size, aggregation, and shape were monitored over 21 days, comparable to a chronic exposure period. Charge stabilized particles (citrate) were more unstable than sterically stabilized particles. Replacement of chloride in the media (due to concerns over chloride-silver interactions) with either nitrate or sulfate resulted in increased shape and dissolution changes. PVP-stabilized NPs in a 10-fold diluted OECD media (chloride present) were found to be the most stable, with only small losses in total concentration over 21 days, and no shape, aggregation, or dissolution changes observed and are recommended for exposure studies.

Green and gentle synthesis of Cu2O nanoparticles using lignin as reducing and capping reagent with antibacterial properties

“…Therefore, the most frequently used method is the chemical reduction, reducing Cu (II) ions to Cu (I) ions, followed by the stabilisation step for the Cu 2 O nanoparticles in the solution. However, the common reducing reagents, such as polyols, [11] sodium citrate, [12] sodium borohydride [13] or other organic matters, may present biological hazards or environmental toxicity. As the global environment is facing with mounting challenges caused by human activity, it is desirable taking into account to use renewable, nontoxic materials and reagents.…”

Assessing nanomaterial exposures in aquatic ecotoxicological testing: Framework and case studies based on dispersion and dissolution

“…Test media properties such as pH (El Badawy et al, 2010) and ionic strength (Harmon et al, 2014;Tejamaya et al, 2012) impact stability. Therefore, while standardized tests typically allow flexibility in selecting from multiple test media types ranging from very soft water to very hard water (e.g., OECD, 2012; USEPA, 2002a), such flexibility is problematic for acquiring consistent (repeatable) results from ENM hazard testing (Petersen et al, 2015).…”

“…If the pH modification failed to increase stability, ionic strength dilutions were employed. Various authors (Romer et al, 2011;Tejamaya et al, 2012) recommended that OECD test media be diluted up to 10-fold to increase ENM stability during bioassays. Similarly, Ma et al (2012) diluted EPA-MHRW fourfold and 100-fold in TiO 2 tests with Daphnia magna and Japanese Medaka, respectively, and pretested both species in the modified media to confirm organism health.…”

Nanopharmaceuticals: Tiny challenges for the environmental risk assessment of pharmaceuticals

“…The basic physical-chemical properties used to characterize small molecules are insufficient for nanomaterials. Further information on particle size and distribution, morphology (e.g., geometry, crystallinity), and surface properties (e.g., chemistry, reactivity, surface area) but also on agglomeration and dissolution behavior is needed for an adequate nanospecific ERA [24,25,26,27,28]. Because nanomaterials for medical purposes are often complex particles (e.g., composed of a core and coating [29]), detailed information on the composition of the compound is also of special importance.…”