Characterization of silver ion dissolution from silver nanoparticles using fluorous-phase ion-selective electrodes and assessment of resultant toxicity to Shewanella oneidensis

Abstract

Silver nanoparticle (Ag NP) dissolution, or ionization from Ag(0) to Ag + , is an important determinant of the nanoparticles' toxicity as silver ions are considered to be a major contributor to Ag NP cytotoxicity. In this work, we characterize ion dissolution from Ag NPs using a selective and dynamic technique, Ag + -selective electrodes (ISEs) with ionophore-doped fluorous sensing membranes. We examined dissolution of various concentrations of Ag NPs (0.3, 3, and 15 mg mL À1 ) in water and bacterial growth medium in real-time. A decrease in the concentration of free Ag + was observed as a result of complexation with components of the growth medium. Overall, a greater percentage of the nanoparticles dissolve in growth medium than water (28% vs. 13%). Individual chemical components of the growth medium were examined for their complexation capability, and it was determined that ammonia-silver complexes are the predominant species of dissolved Ag + , with 8.9% occurring as AgNH 3 + , 87.8% occurring as Ag(NH 3 ) 2 + , and only 3.3% occurring as free Ag + . After characterizing Ag NP dissolution in growth medium, the viability and growth of Shewanella oneidensis, a ubiquitous beneficial bacterium, were monitored upon exposure to the known in situ levels of Ag + and Ag NPs. Ag + and Ag NPs both caused a dose-dependent decrease in bacterial viability and growth rate, though the growth and viability changes upon Ag NP exposure did not correlate with the ISE-measured Ag + . Using ISEs to monitor Ag NP dissolution in the presence of S. oneidensis revealed that the presence of the organisms influences the nanoparticle dissolution profile, a result not previously reported that has significant implications for understanding nanotoxicity. This work lays the foundation for the use of fluorous-phase ISEs as an in situ nanoparticle characterization tool, addressing a critical technology gap in the field of nanoparticle toxicology.

Effects of Humic and Fulvic Acids on Silver Nanoparticle Stability, Dissolution, and Toxicity

“…In the current study, we employ fluorous-phase Ag + ISEs to monitor AgNP dissolution in situ, thereby eliminating the need for sample preparation and reducing potential sampling errors. 25 …”

“…Fluorousphase Ag + ISEs were previously shown to be powerful tools for dynamic monitoring of AgNP dissolution in complex media. 25 …”

Dynamic silver speciation as studied with fluorous-phase ion-selective electrodes: Effect of natural organic matter on the toxicity and speciation of silver

“…There have been few literature precedents with use of commercially available solid-state ISEs to study Ag + speciation (Benoit et al, 2013; Maurer-Jones et al, 2013b;Maurer et al, 2012; Peretyazhko et al, 2014; Sikora and Stevenson, 1988), possibly due to the common issue of solid state ISE biofouling in biological samples (biological molecules such as proteins adsorb strongly through sulfur groups to silver halide and sulfide electrodes) (Buhlmann et al, 1998; Chang et al, 1990; Kulpmann, 1989; Park et al, 1991). ISEs with polymeric sensing membranes suffer less from adsorption, but extraction of lipophilic biological interferents into their sensing membranes can still causing biofouling of these ISEs (Frost and Meyerhoff, 2002; Ward et al, 2003).…”

“…Moreover, fluorous-phase Ag + ISEs offer exceptional Ag + selectivity due to the non-coordinating and poorly solvating properties of the fluorous phase. They also exhibit fast response times (less than 1 s), making them a unique tool for environmental Ag + speciation studies (Boswell and Buhlmann, 2005; Lai et al, 2010; Maurer-Jones et al, 2013b). We used these sensors to study open questions regarding the interaction of Ag + and NOM, specifically the kinetics of Ag + and NOM binding and the correlation between the extent of Ag + binding to NOM and the resulting Ag + toxicity.…”

Nanomaterials

“…87,107 ISE have been used in the study of Ag NM in water and bacterial growth media (ferric citrate) showing that a greater percentage of the NM dissolve in growth media than in water (28 compared to 13%) and that the majority of the dissolved silver is present as ammoniaesilver complexes. 100 This type of quantitative analysis of dissolution has also been applied to ZnO NM using AGNES and will be discussed in more detail later in this chapter (Section 4.5 and Figure 6). 74 These techniques are not universal because first, there are only a limited number of ISE (and interferences) and secondly, AGNES is only relevant for elements that alloy with mercury electrodes i.e.…”