Distinguishing the toxic effects of nanoparticles (NPs) themselves from the well-studied toxic effects of their ions is a critical but challenging measurement for nanotoxicity studies and regulation. This measurement is especially difficult for silver NPs (AgNPs), because dissolved silver forms silver chloride NPs or microparticles in many relevant biological and environmental solutions. Our simulations predict that solid AgCl particles form at silver concentrations greater than 0.18 μg/ml and 0.58 μg/ml in cell culture media and moderately hard reconstituted water (MHRW), respectively. The AgCl NPs are usually not possible to separate from AgNPs, so common existing total silver techniques applied to measure AgNP dissolution such as inductively coupled plasma-mass spectrometry (ICP-MS) or atomic absorption cannot accurately measure the amount of silver remaining in AgNP form, as they cannot distinguish Ag species. In this work, we introduce a simple localized surface plasmon resonance (lSPR) UV-Visible absorbance measurement as a technique to measure the amount of silver remaining in AgNP form for AgNPs whose agglomeration state is constant. Unlike ICP-MS or other existing methods, this method can be used to measure the amount of silver remaining in AgNP form even in biological and environmental solutions containing chloride because AgCl NPs do not have an associated lSPR absorbance. After using ICP-MS to show that the area under the absorbance curve is an accurate measure of silver in AgNP state for unagglomerating AgNPs in non-chloride containing media, we use the absorbance to measure dissolution rates of AgNPs with different polymer coatings in biological and environmental solutions. We show that the proportional dissolution rate decreases at high AgNP concentrations, 5 kDa polyethylene glycol-thiol coatings increase the dissolution rate, and the rate is much higher in cell culture media than in MHRW.
Citation: Analytical Chemistry
Pub Type: Journals
silver colloid, dissolution, silver ion, ICP-MS, localized surface plasmon resonance absorbance