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

Abstract

Understanding the adsorption, distribution, metabolism and excretion (ADME) of engineered nanomaterials (ENMs) in fish has been limited due to analytical constraints in detecting the presence of nanoparticles (NPs) in the tissues. However, single particle inductively coupled plasma mass spectrometry now allows the detection of the particulate silver (Ag) in trout, including the mean particle diameter, mass concentration, and particle number concentration. The aim of this work was to quantify the particulate fraction of Ag in the hind intestine, liver, kidney and carcass following dietary exposure to either no added Ag (control), AgNO₃, Ag NPs or Ag₂S NPs, and whether this changes following a depuration period. Particulate Ag was found in the hind intestine of all treatments, including the AgNO₃ exposure and trace amounts in the controls. At week 4, the particle number concentration (per g dry weight) in the hind intestine was 0.07 ± 0.03 × 10⁹, 318.17 ± 116.71 × 10⁹, 119.51 ± 33.00 × 10⁹ and 0.60 ± 0.22 × 10⁹, for the control, AgNO₃, Ag NPs and Ag₂S NPs exposures, respectively. In the Ag treatments, the organ particle number concentrations for both the AgNO₃ and Ag NPs exposures were significantly higher compared to the Ag₂S NP exposure, indicating a lower bioavailability of the latter material. The presence of particles in the AgNO₃ exposure indicates that particulate Ag can be made in either the gut lumen or within the intestinal tissue. In conclusion, there was detection of silver-containing particles in the organs following exposure to both dissolved and particulate forms of Ag.