In Vivo Tracking of Copper-64 Radiolabeled Nanoparticles in Lactuca sativa

Authors

Ryan A. Davis, Radiochemistry Research and Training Facility
Devin A. Rippner, Department of Land, Air and Water Resources
Sven H. Hausner, Radiochemistry Research and Training Facility
Sanjai J. Parikh, Department of Land, Air and Water ResourcesFollow
Andrew J. McElrone, USDA-ARS
Julie L. Sutcliffe, University of California, Davis

Document Type

Article

Date of this Version

2017

Citation

Environ. Sci. Technol. XXXX, XXX, XXX-XXX.

Comments

U.S. government work.

Abstract

Engineered nanoparticles (NPs) are increasingly used in commercial products including automotive lubricants, clothing, deodorants, sunscreens, and cosmetics and can potentially accumulate in our food supply. Given their size it is difficult to detect and visualize the presence of NPs in environmental samples, including crop plants. New analytical tools are needed to fill the void for detection and visualization of NPs in complex biological and environmental matrices. We aimed to determine whether radiolabeled NPs could be used as a noninvasive, highly sensitive analytical tool to quantitatively track and visualize NP transport and accumulation in vivo in lettuce (Lactuca sativa) and to investigate the effect of NP size on transport and distribution over time using a combination of autoradiography, positron emission tomography (PET)/computed tomography (CT), scanning electron microscopy (SEM), and transition electron microscopy (TEM). Azide functionalized NPs were radiolabeled via a “click” reaction with copper-64 (⁶⁴Cu)-1,4,7-triazacyclononane triacetic acid (NOTA) azadibenzocyclooctyne (ADIBO) conjugate ([⁶⁴Cu]- ADIBO-NOTA) via copper-free Huisgen-1,3-dipolar cycloaddition reaction. This yielded radiolabeled [⁶⁴Cu]-NPs of uniform shape and size with a high radiochemical purity (>99%), specific activity of 2.2 mCi/mg of NP, and high stability (i.e., no detectable dissolution) over 24 h across a pH range of 5−9. Both PET/CT and autoradiography showed that [⁶⁴Cu]-NPs entered the lettuce seedling roots and were rapidly transported to the cotyledons with the majority of the accumulation inside the roots. Uptake and transport of intact NPs was size-dependent, and in combination with the accumulation within the roots suggests a filtering effect of the plant cell walls at various points along the water transport pathway.