Secondary Ion Mass Spectrometry Image Depth Profiling for Visualizing the Uptake and Biodistribution of Gold Nanoparticles in Caenorhabditis elegans

M.E. Johnson, J. Bennett, A.R. Montoro Bustos, S.K. Hanna, A. Kolmakov, N. Sharp, E.J. Petersen, P.E. Lapasset, C.M. Sims, K.E. Murphy, B.C. Nelson
National Institute of Standards & Technology,
United States

Keywords: uptake, nanoparticles, SIMS, single particle ICP-MS, Caenorhabditis elegans

Summary:

Analytical techniques that are capable of determining both the spatial distribution and quantity (mass and/or particle number) of engineered nanomaterials concurrently in organisms are essential for properly characterizing nano-bio interactions and for nanomaterial risk assessments. However, analytical methods that can perform these types of complementary measurements are not readily available. In the present study, we combine the use of dynamic secondary ion mass spectrometry (dynamic SIMS) and single particle inductively coupled mass spectrometry (spICP-MS) techniques to determine the biodistribution and quantity of gold nanoparticles (AuNPs) ingested by Caenorhabditis elegans. We report the application of SIMS in image depth profiling mode for visualizing, identifying, and characterizing the biodistribution of AuNPs ingested by nematodes in both the lateral and z (depth) dimensions. With SIMS, it was possible to clearly identify very small collections of NPs distributed throughout the nematode body. The excellent depth resolution of SIMS allowed us to distinguish between NPs lying in a single plane versus NPs distributed over a range of depths. A three-dimensional representation of a SIMS image stack provided unique insights into the distribution of AuNPs over the entire analyzed volume of the nematode, a nanoscopic visualization not easily achieved by other techniques. In parallel, we utilized spICP-MS and conventional ICP-MS to quantify the mean number of AuNPs within the nematode body, which ranged between 2 and 36 NPs depending on the size of the AuNP; tested sizes were 80 nm, 100 nm, and 150 nm. The complementary data from both SIMS image depth profiling and spICP-MS provides a complete view of the uptake, translocation, and transformation of ingested NPs within Caenorhabditis elegans.