Citation: Sarkar, S.; Vinokur, Z.; Buitrago, B.; Mousa, L.; Sanchez, H.; Basilicata, A.; Douglas, J.-A.; Reddock, S. Imaging of Transmetallation and Chelation Phenomena Involving Radiological Contrast Agents in Mineral-Rich Fruits. Tomography 2022, 8, 1413–1428. https://doi.org/10.3390/ tomography8030114 Academic Editor: Emilio Quaia Received: 17 September 2021 Accepted: 17 May 2022 Published: 23 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Imaging of Transmetallation and Chelation Phenomena Involving Radiological Contrast Agents in Mineral-Rich Fruits Subhendra Sarkar * , Zoya Vinokur , Bleidis Buitrago, Lin Mousa, Hayley Sanchez, Analia Basilicata, Jodi-Ann Douglas and Seanetta Reddock Department of Radiologic Technology & Medical Imaging, New York City College of Technology, City University of New York, New York, NY 11201, USA; zvinokur@citytech.cuny.edu (Z.V.); bleidis.buitrago@mail.citytech.cuny.edu (B.B.); lin.mousa@mail.citytech.cuny.edu (L.M.); hayleysa14@gmail.com (H.S.); analia.basilicata@mail.citytech.cuny.edu (A.B.); jdouglas@citytech.cuny.edu (J.-A.D.); shumphreys@citytecch.cuny.edu (S.R.) * Correspondence: ssarkar@citytech.cuny.edu Abstract: Exogenous heavy metals or non-metallic waste products, for example lanthanide or iodi- nated contrast media for radiological procedures, may interfere with the biochemical pools in patients and in common food sources, creating an excess buildup of exogenous compounds which may reach toxic levels. Although the mechanisms are unknown, our experiments were designed to test if this toxicity can be attributed to “transmetallation” or “chelation” reactions freeing up lanthanides or chelated transition metals in acidic fruits used as phantoms representing the biologically active and mineral-rich carbohydrate matrix. The rapid breakdown of stable contrast agents have been reported at a lower pH. The interaction of such agents with native metals was examined by direct imaging of contrast infused fresh apples and sweet potatoes using low energy X-rays (40–44 kVp) and by magnetic resonance imaging at 1.5 and 3T. The stability of the exogenous agents seemed to depend on endogenous counterions and biometals in these fruits. Proton spin echo MR intensity is sensitive to paramagnetic minerals and low energy X-ray photons are sensitively absorbed by photoelectric effects in all abundant minerals and were compared before and after the infusion of radiologic contrasts. Endogenous iron and manganese are believed to accumulate due to interactions with exogenous iodine and gadolinium in and around the infusion spots. X-ray imaging had lower sensitivity (detection limit approximately 1 part in 10 4 ), while MRI sensitivity was two orders of magnitude higher (approximately 1 part in 10 6 ), but only for paramagnetic minerals like Mn and Fe in our samples. MRI evidence of such a release of metal ions from the native pool implicates transmetallation and chelation reactions that were triggered by infused contrast agents. Since Fe and Mn play significant roles in the function of metalloenzymes, our results suggest that transmetallation and chelation could be a plausible mechanism for contrast induced toxicity in vivo. Keywords: GBCA; transmetallation; environmental toxins; mammographic soft X-ray; gadolinium; iodinated contrast; X-ray; environmental pollution; radiological contrast media; chelation; T 1 and T 2 relaxations; contrast induced toxicity; magnetic resonance imaging 1. Introduction 1.1. Radiological Contrast Agents and Transmetallation: An Environmental Issue Radiological contrast agents have significantly increased the diagnostic utility in the past several decades as well as the buildup of harmful medical waste. However, the risk and mitigation steps are not yet understood without more data on how these agents affect enzyme actions and homeostasis. Out of 75 million yearly CT scans in the US, about half are performed with iodinated X-ray contrast agents [1] that frequently cause mild to moderate adverse reactions and life threatening events occurring at a rate of 1/10,000 [2]. Recently, gadolinium based contrast agents (GBCA, with central lanthanide group metal ion) for MRI Tomography 2022, 8, 1413–1428. https://doi.org/10.3390/tomography8030114 https://www.mdpi.com/journal/tomography