Superparamagnetic Nanostructures for Off‐Resonance Magnetic Resonance Spectroscopic Imaging

Abstract

This study proposes a new method to generate positive contrast in magnetic resonance imaging (MRI) using superparamagnetic contrast agents. Superparamagnetic nanostructures consisting of octahedron manganese ferrite nanoparticles embedded in spherical nanogels are fabricated using a bottom‐up approach. The composite nanoparticles are strongly magnetized in an external magnetic field and produce a unique NMR frequency shift in water protons, which can be demonstrated in MR spectroscopy and imaging to be different from the bulk pool. Moreover, the particles exhibit excellent colloidal stability in aqueous media and good cell biocompatibility. Hence, these particles are potentially useful as biomarkers by taking advantage of the positive contrast effects produced in MRI.

Sensitive T2 MRI Contrast Agents from the Rational Design of Iron Oxide Nanoparticle Surface Coatings

“…Table summarizes the performance ( r 2 ) of the IONC contrast agents examined here compared to previously published reports of single core, spherical IONC of similar structure. ,,− ,− As a group, these IONCs have T 2 relaxivities much greater than commercial agents (<200 mM –1 s –1 ) . In addition, the samples studied here compare well to those reported by others and one, the largest oleic acid bilayer coated sample, has to our knowledge the largest reported r 2 (510.3 mM –1 s –1 ) for spherical iron oxide monocrystals (Table ).…”

“…For larger core materials already optimized for SDR, water permeable polymers have the opposite effect and slow water down so much that the contrast is suppressed, a limit referred to as the echo limited regime (ELR). Materials optimized with both their surface and diameter exhibit performance greater than commercial IONCs (>200 mM –1 s –1 ) and similar IONCs reported in the literature (>385 mM –1 s –1 ). ,,,− ,− Water permeable coatings also affect the size-dependent trends in these systems by shifting SDR, where optimal performance is observed, to smaller core diameters. The accompanying description of these trends showcases the essential role that surface coatings play in CA performance and helps rationalize the existing reports of surface-dependent effects seen in this work as well as the broader literature.…”

“…In addition, the samples studied here compare well to those reported by others and one, the largest oleic acid bilayer coated sample, has to our knowledge the largest reported r 2 (510.3 mM –1 s –1 ) for spherical iron oxide monocrystals (Table ). ,,− ,− Accounting for both core size and saturation magnetization by using the Redfield parameter (Δωτ D ), we can estimate the relevant relaxation regimes for these materials. All these high-performing materials fall just short of the static dephasing regime (Δωτ D ≈ 1).…”

Synthesis of Water-Dispersible Gd2O3/GO Nanocomposites with Enhanced MRI T1 Relaxivity

“…In a control experiment, pluronic F127 polymer encapsulated GDO1 nanoclusters were prepared through a mini-emulsion and solvent evaporation process (MESE), following established protocols . The hydrodynamic size of the as-obtained GDO1/F127 nanoclusters decreased with decreasing particle loading amount (Table S2).…”

Multifunctional PEGylated nanoclusters for biomedical applications

“…At this pH range, due to its harsh condition, the core nanoparticles could be dissolved as well. 51 On the other hand, above pH 13.0, no protonation of carboxylic acid was observed, indicated by the negative charged surface of A-MFNCs. The abrupt size increase indicated that the PMAO-g-PEG host matrix could have swelled and disintegrated, leading to severe core nanoparticle aggregation.…”