Iron Oxide Nanoparticle Based Contrast Agents for Magnetic Resonance Imaging

TLDR

Magnetic iron oxide nanoparticles are extensively studied for applications such as magnetic separation, hyperthermia, and MRI contrast, with many synthesis routes and size-dependent contrast properties. This review aims to describe synthesis methods for magnetic iron oxide nanoparticles and evaluate their use as MRI contrast agents, focusing on extremely small MIONs that overcome limitations of conventional T2 and gadolinium-based T1 agents. The review concentrates on liquid‑phase synthesis approaches—both aqueous and organic—for producing magnetic iron oxide nanoparticles.

Abstract

Magnetic iron oxide nanoparticles (MIONs) have attracted enormous attention due to their wide applications, including for magnetic separation, for magnetic hyperthermia, and as contrast agents for magnetic resonance imaging (MRI). This review article introduces the methods of synthesizing MIONs, and their application as MRI contrast agents. Currently, many methods have been reported for the synthesis of MIONs. Herein, we only focus on the liquid-based synthesis methods including aqueous phase methods and organic phase methods. In addition, the MIONs larger than 10 nm can be used as negative contrast agents and the recently emerged extremely small MIONs (ES-MIONs) smaller than 5 nm are potential positive contrast agents. In this review, we focus on the ES-MIONs because ES-MIONs avoid the disadvantages of MION-based T2- and gadolinium chelate-based T1-weighted contrast agents.