Advances in Applications of Metal Oxide Nanomaterials as Imaging Contrast Agents

Abstract

Medical diagnosis relies on imaging modalities to reveal abnormalities in organs or existence of tumorous lesion. Application of contrast agents alongside imaging techniques is essential in order to obtain high contrast images with distinguishable features. Contrast agents delivered and accumulated in target sites can enhance local signal generation and solve the inherent lack of contrast in imaging techniques. As such, various contrast agents are developed for modalities like computed tomography (CT), magnetic resonance imaging (MRI), and photoacoustic imaging (PAI). For many of these techniques, metal-based agents possess the desired properties for signal and contrast enhancement. Metal oxide nanomaterials present a simple platform for metalbased contrast agents with tunable structure, magnetic and optical properties, surface chemistry, and pharmacokinetics. These can be controlled through synthesis, redox reactions, and surface modification to produce desirable nanoparticles. In this review, recent advances in the development of metal oxide imaging agents are highlighted. Various metal oxide species are discussed, including iron oxides, gadolinium oxides, manganese oxides, tungsten oxides and bronzes, molybdenum oxides, and other oxides of titanium, tantalum, etc. Imaging capability and performance of these metal oxides are presented, and novel functionalization strategies are presented. Finally, recommendations for future research in this area are proposed.

Raman spectra tell us so much more: Raman features and saturation magnetization for efficient analysis of manganese zinc ferrite nanoparticles

“…By doping bulk manganese ferrite with zinc, the saturation magnetization can be improved even above that of magnetite . Manganese ferrite NPs are thus an interesting substrate for biomedical applications, such as hyperthermia treatment or magnetic resonance imaging contrast agent for cancer therapy. Thus, establishing an efficient method for precise, rapid, and non‐destructive characterization of spinel‐structured NPs properties is highly desired.…”

Metal Oxide Nanoparticles: Evidence of Adverse Effects on the Male Reproductive System

“…Medical imaging is essential for medical diagnosis. MONPs have been used as nanoparticle-based contrast agents in multiple modern imaging modalities that allow the visualization of abnormalities, such as tumor lesions or other regions of interest [ 67 ]. Of all the plethora of available NPs, metal oxides have advantages in imaging applications due to their diverse size- and shape-dependent optoelectronic properties [ 27 , 68 ] and high stability, which are not achievable with traditional lipid or polymer-based nanoparticles [ 69 ].…”

Gd3+ Doped CoFe2O4 Nanoparticles for Targeted Drug Delivery and Magnetic Resonance Imaging

“…For the estimation of the utility of CAs in relaxation r 1 or r 2 , the soothing ratio is a significant parameter: The more calming the agent is, the more efficient the agent can contrast T 2 [25]. The relaxivity ratio higher than 10 generally suggests a good T 2 imaging ability of CAs, while a relaxivity ratio less than 5 indicates the capability for T 1 imaging [26,55,56]. The MRI contrast enhancement relies upon the particle size, magnetic properties, surface composition and charge of the material.…”