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

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 ( 64 Cu)-1,4,7-triazacyclononane triacetic acid (NOTA) azadibenzocyclooctyne (ADIBO) conjugate ([ 64 Cu]-ADIBO-NOTA) via copper-free Huisgen-1,3-dipolar cycloaddition reaction. This yielded radiolabeled [ 64 Cu]-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 [ 64 Cu]-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.

Nanoparticle-Based Sustainable Agriculture and Food Science: Recent Advances and Future Outlook

“…The combined use of 2-D (DF-HSI) and 3-D (nano-CT) techniques provides better means to characterize and evaluate the NPplant interaction at the cellular level (Avellan et al, 2017). Another non-invasive, highly sensitive method to visualize NPs through the combination of autoradiography, positron emission tomography (PET)/CT, TEM, and SEM was demonstrated in lettuce (Lactuca sativa) (Davis et al, 2017). In a pioneering study, the effect and interaction of TiO 2 NPs with garlic (Allium sativum) was observed through spectroscopic techniques using time-resolved, laser-induced fluorescence and ultravioletvisible spectra.…”

From the Outside in: An Overview of Positron Imaging of Plant and Soil Processes

“…The application of positron imaging to plant studies has increased significantly since the initial water transport analyses by McKay et al 2 While dynamics of water movement with PET in plants has been widely studied, [25][26][27][28][29][30][31][32][33][34][35] other topics related to PET have increasingly been investigated, including uptake and translocation of nutrients, [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]98,99 photoassimilate fixation/allocation, 15,22,23, sugar transport, 21,[82][83][84][85][86][87] and heavy metal contaminant uptake and transport 25,[88][89][90][91][92][93]…”

“…Davis et al used autoradiographic, PET/CT, and electron imaging approaches to study the uptake and translocation of functionalized, nanoparticulate [ 64 Cu]CuO by lettuce (Lactuca sativa). 88 Nanoparticles were observed to enter seedlings through the roots, where much of the 64 Cu accumulated, with some subsequent translocation to cotyledons. Dosing concentration of nanoparticles did not impact translocation within lettuce seedlings, but nanoparticle size did, with greater amounts of smaller (% 10 nm) nanoparticles taken up over a longer period of time relative to larger particles (% 20 nm).…”

Harnessing the Coordination Chemistry of 1,4,7‐Triazacyclononane for Biomimicry and Radiopharmaceutical Applications

“…Similarly, the isothiocyanate‐functionalised TACN derivatives 45 , 50 – 54 , and 65 can be linked to amino‐terminated biomolecules via highly stable thiourea bonds . Over the last decade, “clickable” versions of BFCAs have also been used for tagging different biomolecules and nanoparticles to allow PET imaging using 64 Cu . Examples of these include ligands 55 , 56 and 60 for rapid conjugation to specific peptides by Cu I ‐catalysed click reaction, and strained cyclooctynes 57 – 59 for copper‐free attachment to azide‐functionalised peptides, proteins and nanoparticles.…”

“…Over the last decade, “clickable” versions of BFCAs have also been used for tagging different biomolecules and nanoparticles to allow PET imaging using 64 Cu . Examples of these include ligands 55 , 56 and 60 for rapid conjugation to specific peptides by Cu I ‐catalysed click reaction, and strained cyclooctynes 57 – 59 for copper‐free attachment to azide‐functionalised peptides, proteins and nanoparticles. Also, tetrazine‐bearing NOTA derivatives 61 and 62 have been used for linking trans ‐cyclooctene‐functionalised antibodies using inverse‐electron‐demand Diels–Alder reactions …”