Magnetic resonance imaging (MRI), an all-pervasive imaging modality, shows precise inner body architecture using nuclear magnetic resonance (NMR) theory coupled with gradient magnetic fields. MRI as an imaging technique depends on protons' spin density, along with the lengthening (T1) and slicing (T2) relaxation time to distinguish tissues.
The role of MRI contrast agents is crucial in enhancing this tissue contrast, enabling clearer delineation of structures. Metal-based nanoparticles, in particular, are a novel generation of MRI contrast agents because they are able to function magnetically, are biocompatible, and are functionalizable. Alfa Chemistry is exploring these nanoparticles' properties, uses, and classifications in detail for MRI applications in this article from Alfa Chemistry.
Manganese-based Nanoparticles
Nanoparticles containing manganese (Mn) such as MnO have the potential as T1-weighted MRI agents. Manganese ions (Mn2+) are paramagnetic and will get into cells via calcium channels to sharpen MRI contrast and enable functional brain imaging. Manganese ions, in contrast to gadolinium, are more benign and do not require chelation, so don't need fancy chemical synthesis. This means that it can sometimes be used instead of gadolinium.
Manganese-enhanced MRI (MEMRI) has performed well in animal models (particularly in neuroimaging). It has been shown that manganese-doped graphene oxide composites can be formulated as potent contrast agents that are stable and bioavailable.
Iron Oxide Nanoparticles
MRI contrast agent with one of the most widespread uses is Iron oxide nanoparticles (Fe3O4/γ-Fe2O3). Nanoparticles of iron oxide are biocompactible and magnetic, and commonly deployed in T2-weighted imaging as superparamagnetic iron oxide (SPIO) and ultra-small superparamagnetic iron oxide (USPIO). These agents are colloidal suspensions of iron oxide nanoparticles that, when applied to MRI, darken the T2 signal in the tissue they're incorporated into, and hence the tissue darkens. SPIO and USPIO drugs are specifically suited for liver tissue, which is why they are so useful in liver tumor diagnosis.
