High throughput laser ablation ICP-MS bioimaging of silver distribution in animal organisms and plant tissue after exposure to silver sulfide nanoparticles

Abstract

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a method with high potential to visualize the distribution of elements in different samples, including a variety of organisms. This study aimed to demonstrate the broad application of LA-ICP-MS in nanomaterial-biota fate studies as a high throughput bioimaging tool and to broaden the choice of standard organism models in material-biota interaction research. In this study, operation parameters of LA-ICP-MS were optimised on one organism, woodlice Porcellio scaber. Subsequently, the scanning conditions were tested on a range of aquatic (Girardia tigrina, Lumbriculus variegatus, and Oncorhynchus mykiss), terrestrial organisms (Lumbricus rubellus, Porcellio scaber) and one plant (Triticum aestivum) upon exposure to Ag₂S nanoparticles (NPs) and silver nitrate (AgNO₃). Model organisms were exposed in aquatic or terrestrial mesocosm experiments where nominal concentrations of Ag were 10 μg Ag per L of water and 10 mg Ag per kg of soil, respectively. The results showed that both sample preparation and LA-ICP-MS imaging conditions, as optimized on the selected organism (65 μm laser diameter, scan rate 100 μm s⁻¹, measuring duration 35 min), are applicable on different tissues. These LA-ICP-MS imaging conditions enable recognition of the main biological structures and biodistribution of elements of interest. By using fast-screening LA-ICP-MS, we confirmed the presence of Ag₂S NPs on the body surface or in the gut lumen (adsorbed and retained), but not in other internal parts of organisms, which is consistent with our previous toxicokinetic studies. The presence of Ag was also confirmed in some parts of wheat roots. The advantage of this technique is the possibility of sequential use of fast- and slow-scanning steps to optimise the duration of analysis and data processing, whilst also improving cost-effectiveness without compromising the quality of results.