Nanoscale Contrast Agents for Magnetic Resonance Imaging: A Review

Abstract

Today, magnetic resonance imaging (MRI) is one of the most widely applied noninvasive clinical imaging modalities with excellent applicability in bio- and nanomedicine, particularly in specific detecting and high-quality three-dimensional imaging of tumors/cancers. In this context, the design of efficient nanoscale contrast agents (NCAs) for MM with high magnetic relaxivity and specificity/selectivity has garnered immense interest deploying a variety of innovatively designed nanostructures. Some important characteristics of NCAs such as biocompatibility, improved relaxivity, high dispersibility, specific targeting, and low toxicity make them ideal candidates for imaging/biosensing applications. The hybridization and surface functionalization/modification of these materials by applying suitable functional groups/agents can help to improve their properties and multifunctionality. However, there is still a long way to go in the clinical applications of these nanoagents to serve as a substitute for Gd-based contrast agents or other commercial materials. Importantly, nanotoxicological and biosafety issues of these NCAs need to be systematically addressed both at pre- and clinical stages; construction of smart multifunctional NCAs with clinical diagnostic and imaging potentials is thus warranted. Herein, recent advancements related to the diagnostic and imaging applications of MRI NCAs are deliberated, focusing on important challenges and future directions.