Development of a suitable detection method for silver nanoparticles in fish tissue using single particle ICP-MS

Abstract

A strong alkali extraction technique and suitable single particle ICP-MS method is described for the routine quantifying of particle number concentration, particle size and particle mass concentration for silver nanomaterials in fish tissue.

Quantification of particulate Ag in rainbow trout organs following dietary exposure to silver nitrate, or two forms of engineered silver nanoparticles

“…A validated method to routinely extract and detect nano silver from fish tissues has been documented, 10 with the extractions here performed in exactly the same manner. A stock of 25 mmol L −1 CaCl 2 (Sigma-Aldrich, CAS number 10035-04-8) was made in ultrapure water and diluted with 25% TMAH (Sigma-Aldrich, CAS number 75-59-2) to make an extraction solution of 20% TMAH containing 5 mmol L −1 CaCl 2 .…”

“…For all sample analysis by spICP-MS, an iCAP RQ ICP-MS instrument (Thermo Fisher), fitted with a Micromist nebuliser and a quartz cyclonic spray chamber cooled to 2°C was operated in standard mode. 10 Prior to use, the spray chamber was removed and washed in 10% nitric acid for 30 min, and the peristaltic tubing was replaced each day. The plasma power was 1550 Watts and the plasma, nebulizer and auxiliary gas flow rates were 14.0, 1.06 and 0.8 L min −1 , respectively.…”

“…Each sample produced 20 000 data points which were used to calculate the particle mass concentration, particle number concentration and mean particle size using a bespoke Excel spreadsheet, according to Peters et al 19 and assessed in Clark et al 10 The resulting standardised particle number and particle mass concentrations (per g dry weight of original tissue) were correlated with those of total Ag measurements made on the same organ. 9 The limit of detection for particle size was calculated by using the lowest signal possible in a dwell time (333 counts per second [CPS]) and calculating the particle size for this signal.…”

“…However, it has been shown that particles are present in the livers of fish after 2 weeks exposure to either AgNO 3 or Ag NPs. 10 The presence of particles in the tissues from the AgNO 3 exposure suggests the dissolved metal is transformed to particulate silver either in the gut lumen of the intestine, and/or inside the internal organs. Such transformative processes from feed to tissue are not typically considered for ADME studies in fish, but it is clear that the notion of particle dissolution then ionic uptake of free metal is an oversimplification.…”

The gut barrier and the fate of engineered nanomaterials: a view from comparative physiology

“…Alkaline pH values are also found in the intestines of fish and mammals, as well as parts of the gut in invertebrate species, with the intestinal fluid in fish reaching pH 8.5, and in posterior midgut of springtails reaching pH 8.8 ( Table 1). Such alkaline conditions may preserve at least metal ENMs, since strong alkaline digestion methods are used to extract 'intact' ENMs from tissue (e.g., Ag NPs from fish liver, 56 ). However, the extreme ranges of pH from acid to alkaline would suggest that at some point during the transit through the gut, the ENM will be at a pH value close to its zero point of charge, where particle settling due to aggregation may occur.…”