Spatial Organization of Superparamagnetic Iron Oxide Nanoparticles in/on Nano/Microsized Carriers Modulates the Magnetic Resonance Signal

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) are often encapsulated into drug-carrying nano/microsized particles for simultaneous magnetic resonance (MR) imaging and treatment of diseased tissues. Unfortunately, encapsulated SPIONs may have a limited ability to modulate the T 2 -weighted relaxation of water protons, but this insight has not been examined systematically.This study demonstrates that SPIONs immobilized on 200 nm diameter poly(lactic-co-glycolic acid) (PLGA) nanoparticles using Pickering emulsification present 18-fold higher relaxivity than encapsulated SPIONs and 1.5-fold higher relaxivity than free SPIONs.

Polymer-Assisted Magnetic Nanoparticle Assemblies for Biomedical Applications

“…On the basis of the above principles, Schmidtke et al improved the T 2 MR contrast performance of amphiphilic PI- b -PEG diblock copolymer-based magnetic nanoclusters by elevating the SPIONs loading density and increasing the cluster size in the assemblies. Similar effect was also observed in a triblock copolymer PEI- b -PCL- b -PEG encapsulated FeO x -NPs and PLGA immobilized SPIONs systems, which can further be utilized for the construction of T 2 MR contrast agents . Especially, some smart MR contrast agents that possess biological stimulus groups shed lights on the selective amplification of S/N ratio in the specific lesion sites.…”

“…Similar effect was also observed in a triblock copolymer PEI-b-PCL-b-PEG encapsulated FeO x -NPs 7 and PLGA immobilized SPIONs systems, which can further be utilized for the construction of T 2 MR contrast agents. 134 Especially, some smart MR contrast agents that possess biological stimulus groups shed lights on the selective amplification of S/N ratio in the specific lesion sites. For example, MNP assemblies were prepared and served as a novel MRI probe for cerebral ischemia detection (Figure 7a).…”

Structure-Correlated Magnetic Resonance Transverse Relaxivity Enhancement in Superparamagnetic Ensembles with Complex Anisotropy Landscape

“…Hence, the shape of constituent nanoparticles in their ensemble framework with reduced symmetry of induced local field plays a critical role, because of magnetic field coupling between adjoining nanoparticles. Classical electrodynamic theory also explains that, except for ellipsoidal-shaped systems, all other distorting shapes require extra energy in order to stabilize the magnetic anisotropy. − Furthermore, the type of spin orientation, the distance between consecutive spins, and the relative motion of spins in such complex ensembles can influence proton–electron/proton–proton interaction, which further impacts on transverse relaxation. Hence, we require detailed exploration on the correlation between structure-regulated physical properties and transverse MRI contrast enhancement by considering differently organized ensembles of both isotropic and anisotropic nanosystems.…”

Advances in nanotechnology-based targeted-contrast agents for computed tomography and magnetic resonance

“…3 Nano-formulations have garnered significant attention in basic research into disease diagnosis and treatment owing to their unique properties, including enhanced permeability and retention (EPR) in solid tumors and surface modifiability. 4–47 Research into the development of more targeted nano-enhanced contrast agents aims to combine the potential advantages of nanomaterials to overcome the shortcomings of traditional small-molecule contrast agents, such as rapid metabolism and poor targeting. Improvement of the diagnostic ability and level of medical imaging has become an important research area in the preparation of medical imaging-enhanced contrast agents.…”