The Evolution of Iron Oxide Nanoparticles as MRI Contrast Agents
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.311
The Evolution of Iron Oxide Nanoparticles as MRI Contrast Agents 1
Aileen O’Shea, MB BCh BAO
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Anushri Parakh, MBBS MD
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Rita Maria Lahoud, MD
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Sandeep Hedgire, MD
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Mukesh G Harisinghani, MD
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Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
Abstract
While the use of iron oxide nanoparticles as magnetic resonance contrast agents for clinical imaging is established, they are more recently experiencing renewed interest as alternatives to gadolinium-based contrast agents. Ultra-small iron oxide nanoparticles have unique pharmacokinetics, metabolic and imaging properties. These properties have led to improved techniques for imaging a variety of vascular, oncologic and inflammatory conditions with iron oxide nanoparticles. Current research efforts are aimed at harnessing the characteristics of these nanoparticles to advance magnetic resonance imaging techniques and explore new therapeutic potentials. While there are some limitations to the use of iron oxide nanoparticles, including allergies to parenteral iron and iron storage disorders, the practicable applications for these agents will continue to 1
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expand. The purpose of this review is to provide a brief overview of the history and synthesis of iron oxide nanoparticles, their current applications in clinical imaging and their prospective clinical applications.
INTRODUCTION In the field of nanomedicine, the development and refinement of iron oxide nanoparticles over the last two decades is amongst the best examples of the convergence of nanomaterials and medical imaging [1]. As opposed to the mechanism of T1 shortening produced by gadolinium-based contrast agents (GBCAs), most iron oxide nanoparticles provide a negative contrast agent through T2 and T2* effects. A central tenet for the successful utilization of iron oxide nanoparticles as MR contrast agents is their superparamagnetic effect. In the absence of an applied magnetic field, the superparamagnetic particles are free to rotate independently, due to ambient temperature effects, with no net magnetic field produced [2]. However, upon application of an external magnetic field the magnetic domains of the superparamagnetic particles reorient in a fashion similar to paramagnetic substances to produce an overall net magnetization. Upon removal of the magnetic field, a superparamagnetic particle once again loses its net magnetization as they lose their collective orientation i.e. the net magnetic moment returns to zero[2]. Superparamagnetic particles typically comprise nanocrystalline iron oxides, covered with a protective coating such as dextran (Fig. 1) [3]. The carbohydrate coating is typically linked to the iron oxide core via non-covalent bond
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