Magnetic Nanomaterials as Contrast Agents for MRI

Abstract

Magnetic Resonance Imaging (MRI) is a powerful, noninvasive and nondestructive technique, capable of providing three-dimensional (3D) images of living organisms. The use of magnetic contrast agents has allowed clinical researchers and analysts to significantly increase the sensitivity and specificity of MRI, since these agents change the intrinsic properties of the tissues within a living organism, increasing the information present in the images. Advances in nanotechnology and materials science, as well as the research of new magnetic effects, have been the driving forces that are propelling forward the use of magnetic nanostructures as promising alternatives to commercial contrast agents used in MRI. This review discusses the principles associated with the use of contrast agents in MRI, as well as the most recent reports focused on nanostructured contrast agents. The potential applications of gadolinium- (Gd) and manganese- (Mn) based nanomaterials and iron oxide nanoparticles in this imaging technique are discussed as well, from their magnetic behavior to the commonly used materials and nanoarchitectures. Additionally, recent efforts to develop new types of contrast agents based on synthetic antiferromagnetic and high aspect ratio nanostructures are also addressed. Furthermore, the application of these materials in theragnosis, either as contrast agents and controlled drug release systems, contrast agents and thermal therapy materials or contrast agents and radiosensitizers, is also presented.

The twin cytokines interleukin-34 and CSF-1: masterful conductors of macrophage homeostasis

“…Based on light irradiation from the ultraviolet, visible, and near-infrared spectrums, optical imaging techniques have high detection sensitivity but are limited by quenching and the photo-bleaching effect. Magnetic resonant imaging (MRI) is a radiation-free and non-invasive technique based on magnetic contrast agents such as Gadolinium (III), superparamagnetic iron oxide nanoparticles (SPIO), or perfluorocarbons (PFCs), and is characterized by high spatial resolution but with very low sensitivity 185 , 186 , 187 , 188 . Ionizing radiation such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are based on the use of high-energy elements (radioisotopes) characterized by high-detection sensitivity (from nanomolar to picomolar) but with low spatial resolution 189 , 190 .…”

Magnetic Nanoparticles in Biology and Medicine: Past, Present, and Future Trends

“…Being developed as gadolinium-free alternatives to GCs, iron oxide particles (IOP) garnered clinical interest as MRI contrast agents because of their useful magnetic properties, unique biodistribution and pharmacokinetic profiles, targeting potential, and biocompatibility [ 78 ]. Early successes with superparamagnetic iron oxide nanocrystals (SPIONs, D H > 50 nm) and ultrasmall SPIONs (USPIONs, D H < 50 nm) led to the development of IOP with more robust synthetic approaches and a range of physiochemical, magnetic, biodistribution, and pharmacokinetic properties ( Table 1 ).…”

Imaging Constructs: The Rise of Iron Oxide Nanoparticles

“…Many review papers have described different techniques for synthesis of iron oxide cores in general, or as comparative studies, pointing out the main properties, advantages and disadvantages for each method. As such, this review presents only magnetic particles reportedly in use as contrast agents [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

“…Another significant review paper is that of Caspani et al [ 21 ], published in 2020. In addition to the principles associated with the use of contrast agents in MRI, their review discussed iron oxide nanoparticle synthesis methods, associated with their shape, properties, and their T 1 and/or T 2 capability.…”