Iron Oxide Nanoparticles: An Alternative for Positive Contrast in Magnetic Resonance Imaging

Abstract

Iron oxide nanoparticles have been extensively utilised as negative (<i>T</i>₂) contrast agents in magnetic resonance imaging. In the past few years, researchers have also exploited their application as positive (<i>T</i>₁) contrast agents to overcome the limitation of traditional Gd³⁺ contrast agents. To provide <i>T</i>₁ contrast, these particles must present certain physicochemical properties with control over the size, morphology and surface of the particles. In this review, we summarise the reported <i>T</i>₁ iron oxide nanoparticles and critically revise their properties, synthetic protocols and application, not only in MRI but also in multimodal imaging. In addition, we briefly summarise the most important nanoparticulate Gd and Mn agents to evaluate whether <i>T</i>₁ iron oxide nanoparticles can reach Gd/Mn contrast capabilities.