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.
Highlights
Magnetic Resonance Imaging (MRI) is one of the most powerful techniques in medical imaging, due to its noninvasiveness and radiation-free nature
synthetic antiferromagnetic (SAF) are a novel type of magnetic nanoparticle; their structure consists of two ferromagnetic layers separated by a nonmagnetic one
Dual T1 /T2 MRI contrast agents were obtained, and it was observed that the SPIONs, with the application of an alternating magnetic field, were able to produce an increase in the local temperature that was sufficient to trigger a phase transition of specific hydrogels; in this context, the leak of SPIONs from the hydrogel compounds upon the application of an alternating magnetic field could a successful step in the development of more powerful theragnostic systems
Summary
Magnetic Resonance Imaging (MRI) is one of the most powerful techniques in medical imaging, due to its noninvasiveness and radiation-free nature. In recent decades, several types of contrast agents have been developed to improve the MRI sensitivity and enhance the information present in the images, namely by using magnetic ions and magnetic nanoparticles (NPs) [2]. Materials 2020, 13, 2586 been developed and approved as possible substitutes for GBCAs. Materials 2020, 13, 2586 been developed and approved as possible substitutes for GBCAs Such particles have distinct characteristics, namely, biocompatibility, easy metabolization, high saturation magnetic moments that can be controlled by tuning the particle size and composition, and easy surface functionalization [5]. These contrast agents were not commercially successful [3]. The use of these nanostructures in both cancer diagnosis and therapeutics will be discussed
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