The increased use of engineered nanomaterials (ENMs) in consumer products and the relative lack of understanding of their potential toxicity necessitates further investigation of the interactions between ENMs and environmental and biological systems. Dietary uptake is one of the main exposure routes for trophic transfer to higher organisms. Within nano-uptake studies, the key factor toward mitigating artifactual results is efficient separation of the biological organism and the un-ingested nanomaterial post-exposure. Here we measure the uptake of gold nanoparticles into a model organism, Caenorhabditis elegans (C. elegans), through the combination of an isopycnic sucrose density gradient separation, total particle uptake measurements by conventional ICP-MS, and particle distribution via spICP-MS. It was found that common washing procedures were ineffective at removing excess suspended AuENPs after exposure. Therefore, a sucrose density gradient centrifugation separation was developed and optimized to separate nematodes from AuENPs freely suspended in the exposure media. Quantification of total Au uptake in dry samples was performed following acid digestions of control and Au exposed C. elegans, while an alkaline digestion of biological tissue was optimized for the removal of C. elegans. Finally, size distributions and particle number concentrations were determined for all ENPs dispersed in water and exposure media, as well for ENPs ingested by C. elegans. Ultimately, we found that nematodes showed a preference for larger particle sizes as more 60 nm AuENPs were measured in C. elegans samples in comparison to the 30 nm ENPs over the same exposure period. The described methodology for the separation and in vivo determination of ENPs in multicellular organisms may allow more critical studies of ENP uptake and possibly ENP transformation in other biologically relevant organisms.

Facile separation, sizing, and quantitative analysis of engineered nanoparticles in an organism model using single particle ICP-MS

251st National Meeting (2016)

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