Hybrid magnetic nanostructures (MNS) for magnetic resonance imaging applications

Abstract

The development of MRI contrast agents has experienced its version of the gilded age over the past decade, thanks largely to the rapid advances in nanotechnology. In addition to progress in single mode contrast agents, which ushered in unprecedented R1 or R2 sensitivities, there has also been a boon in the development of agents covering more than one mode of detection. These include T1-PET, T2-PET T1-optical, T2-optical, T1–T2 agents and many others. In this review, we describe four areas which we feel have experienced particular growth due to nanotechnology, specifically T2 magnetic nanostructure development, T1/T2-optical dual mode agents, and most recently the T1–T2 hybrid imaging systems. In each of these systems, we describe applications including in vitro, in vivo usage and assay development. In all, while the benefits and drawbacks of most MRI contrast agents depend on the application at hand, the recent development in multimodal nanohybrids may curtail the shortcomings of single mode agents in diagnostic and clinical settings by synergistically incorporating functionality. It is hoped that as nanotechnology advances over the next decade, it will produce agents with increased diagnostics and assay relevant capabilities in streamlined packages that can meaningfully improve patient care and prognostics. In this review article, we focus on T2 materials, its surface functionalization and coupling with optical and/or T1 agents.

Gd-Doped Superparamagnetic Magnetite Nanoparticles for Potential Cancer Theranostics

“…Even though both T 1 and T 2 mapping are powerful techniques, single-mode contrast agents are not always sufficient in modern diagnosis as they have certain drawbacks and limitations [118]. For example, the dark contrast produced by T 2 agents can also be generated from adjacent bones or vascular or there can be susceptibility artifacts due to the sharp change in magnetic field at the surrounding contrast agent.…”

“…Thus, there is a growing interest in developing complementary T 1 -T 2 dual-modal contrast agents, combining the advantages of positive and negative contrasts to obtain high sensitivity and biocompatibility for improved diagnosis [119]. Two different approaches of integrating T 1 and T 2 species have been reported recently [118]. One is constructed by labeling T 1 -signaling elements (Gd species) on magnetic nanoparticles.…”

Lipid-coated iron oxide nanoparticles for dual-modal imaging of hepatocellular carcinoma

“…Compared with gadolinium-based MRI contrast agents, including Magnevist ® (Gd-DTPA; Bayer Schering Pharma, Berlin, Germany) and Multihance ® (Gd-BOPTA; Bracco Diagnostics Inc., Princeton, NJ, USA), 14,15 superparamagnetic iron oxide NPs have been intensively investigated as promising MRI probes because of their biocompatibility and safety profiles as well as suitable magnetic properties. [16][17][18] However, limitations such as low sensitivity have hindered the further application of MRI as the sole methodology in the diagnosis…”

Engineered ferritin nanocages as natural contrast agents in magnetic resonance imaging

“…MNS based contrast agents show signicantly higher relaxivity and biocompatibility than gadolinium-based complexes. [7][8][9] However, clinical use of MNS based contrast agents has been limited due to translational hurdles such as signal sensitivity, biodistribution, and pharmacokinetics.…”