Topology-dependent T2 relaxivity in Fe3O cluster-based MOFs for enhanced tumor monitoring via MRI

Metal-organic frameworks (MOFs) are crystalline porous materials with tunable structures, where metal ions or clusters serve as magnetic centers and organic ligands offer spatial separation. These characteristics, combined with their diverse topologies, make MOFs promising candidates for contrast agents (CAs) in magnetic resonance imaging (MRI). Herein we synthesized four MOFs based on the same triangular Fe3O clusters with different topologies: MIL-101(Fe) (moo net), MIL-100(Fe) (mtn net), MIL-59(Fe) (pcu net), and MIL-88B(Fe) (acs net). To clarify the relationship between topologies and T2 relaxivities, the MOFs were tailored into uniform, nanoscale spherical morphologies. Notably, the value of T2 relaxivity for MIL-88B(Fe) with acs topology is nearly three times that for MIL-101(Fe) with moo topology at 7.0 T. By comparing the magnetic properties of Fe3O molecular clusters and Ga-doped MIL-88B(Fe), our analysis demonstrated the significant advantage of MOFs with fixed arrays, adjustable components and diverse topologies in enhancing magnetic relaxation. Cellular MRI experiments further revealed that MIL-88B(Fe) could differentiate between M1 and M2 macrophages, highlighting its potential for monitoring tumor progression. These findings offer valuable insights into how MOF topology can be strategically utilized to enhance T2 relaxivities for MRI applications.

Ultrasmall superparamagnetic iron oxide nanoparticles: A next generation contrast agent for magnetic resonance imaging

As a research hotspot, the development of magnetic resonance imaging (MRI) contrast agents has attracted great attention over the past decades for improving the accuracy of diagnosis. Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with core diameter smaller than 5.0 nm are expected to become a next generation of contrast agents owing to their excellent MRI performance, long blood circulation time upon proper surface modification, renal clearance capacity, and remarkable biosafety profile. On top of these merits, USPIO nanoparticles are used for developing not only T₁ contrast agents, but also T₂ /T₁ switchable contrast agents via assembly/disassembly approaches. In recent years, as a new type of contrast agents, USPIO nanoparticles have shown considerable applications in the diagnosis of various diseases such as vascular pathological changes and inflammations apart from malignant tumors. In this review, we are focusing on the state-of-the-art developments and the latest applications of USPIO nanoparticles as MRI contrast agents to discuss their advantages and future prospects. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Diagnostic Applications of Ultrasmall Superparamagnetic Particles of Iron Oxide for Imaging Myocardial and Vascular Inflammation

Cardiac magnetic resonance (CMR) is at the forefront of noninvasive methods for the assessment of myocardial anatomy, function, and most importantly tissue characterization. The role of CMR is becoming even more significant with an increasing recognition that inflammation plays a major role for various myocardial diseases such as myocardial infarction, myocarditis, and takotsubo cardiomyopathy. Ultrasmall superparamagnetic particles of iron oxide (USPIO) are nanoparticles that are taken up by monocytes and macrophages accumulating at sites of inflammation. In this context, USPIO-enhanced CMR can provide valuable additional information regarding the cellular inflammatory component of myocardial and vascular diseases. Here, we will review the recent diagnostic applications of USPIO in terms of imaging myocardial and vascular inflammation, and highlight some of their future potential.