Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

• Published in: Dalton transactions : an international journal of inorganic chemistry 2014-06, Vol.43 (22), p.8395-8404
• Main Authors: Kostopoulou, Athanasia, Velu, Sabareesh K P, Thangavel, Kalaivani, Orsini, Francesco, Brintakis, Konstantinos, Psycharakis, Stylianos, Ranella, Anthi, Bordonali, Lorenzo, Lappas, Alexandros, Lascialfari, Alessandro
• Format: Article
• Language: English
• Subjects: Animals; Assemblies; Cell Culture Techniques; Cell Proliferation - drug effects; Cell Survival - drug effects; Clusters; Colloids; Contrast agents; Ferric Compounds - chemistry; Ferric Compounds - toxicity; Hydrophobic and Hydrophilic Interactions; Magnetic Phenomena; Magnetic resonance; Magnetic Resonance Spectroscopy; Magnetization; Mice; Microscopy, Electron, Transmission; Nanocrystals; Nanoparticles - chemistry; Nanoparticles - toxicity; NIH 3T3 Cells; Nuclear magnetic resonance; Particle Size; Surface Properties
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00024b

An elevated-temperature polyol-based colloidal-chemistry approach allows for the development of size-tunable (50 and 86 nm) assemblies of maghemite iso-oriented nanocrystals, with enhanced magnetization. (1)H-nuclear magnetic resonance (NMR) relaxometric experiments show that the ferrimagnetic cluster-like colloidal entities exhibit a remarkable enhancement (4-5 times) in transverse relaxivity when compared to that of the superparamagnetic contrast agent Endorem®, over an extended frequency range (1-60 MHz). The marked increase in the transverse relaxivity r2 at a clinical magnetic field strength (∼1.41 T), which is 405.1 and 508.3 mM(-1) s(-1) for small and large assemblies, respectively, makes it possible to relate the observed response to the raised intra-aggregate magnetic material volume fraction. Furthermore, cell tests with a murine fibroblast culture medium confirmed cell viability in the presence of the clusters. We discuss the NMR dispersion profiles on the basis of relaxivity models to highlight the magneto-structural characteristics of the materials for improved T2-weighted magnetic resonance images.