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Nanoprobes with multimodal functionality have attracted significant interest recently because of their potential applications in nanomedicine. This paper reports the successful development of lanthanide-doped Y2O3 nanoprobes for potential applications in optical and magnetic resonance (MR) imaging. The morphology, structural, and optical properties of these nanoprobes were characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and photoluminescence (PL). The cytotoxicity test showed that the prepared lanthanide-doped Y2O3 nanoprobes have good biocompatibility. The obvious contrast enhancement in the T1-weighted MR images suggested that these nanoprobes can be used as a positive contrast agent in MRI. In addition, the clear fluorescence images of the L-929 cells incubated with the nanoprobes highlight their potential for optical imaging. Overall, these results suggest that prepared lanthanide-doped Y2O3 nanoprobes can be used for simultaneous optical and MR imaging. [ABSTRACT FROM AUTHOR]

Abstract: We introduce a new category of nanoparticle-based T 1 MRI contrast agents (CAs) by encapsulating paramagnetic chelated gadolinium(III), i.e., Gd3+·DOTA, through supramolecular assembly of molecular building blocks that carry complementary molecular recognition motifs, including adamantane (Ad) and β-cyclodextrin (CD). A small library of Gd3+·DOTA-encapsulated supramolecular nanoparticles (Gd3+·DOTA⊂SNPs) was produced by systematically altering the molecular building block mixing ratios. A broad spectrum of relaxation rates was correlated to the resulting Gd3+·DOTA⊂SNP library. Consequently, an optimal synthetic formulation of Gd3+·DOTA⊂SNPs with an r 1 of 17.3 s−1 mM−1 (ca. 4-fold higher than clinical Gd3+ chelated complexes at high field strengths) was identified. T 1-weighted imaging of Gd3+·DOTA⊂SNPs exhibits an enhanced sensitivity with a contrast-to-noise ratio (C/N ratio) ca. 3.6 times greater than that observed for free Gd3+·DTPA. A Gd3+·DOTA⊂SNPs solution was injected into foot pads of mice, and MRI was employed to monitor dynamic lymphatic drainage of the Gd3+·DOTA⊂SNPs-based CA. We observe an increase in signal intensity of the brachial lymph node in T 1-weighted imaging after injecting Gd3+·DOTA⊂SNPs but not after injecting Gd3+·DTPA. The MRI results are supported by ICP-MS analysis ex vivo. These results show that Gd3+·DOTA⊂SNPs not only exhibits enhanced relaxivity and high sensitivity but also can serve as a potential tool for diagnosis of cancer metastasis. [ABSTRACT FROM AUTHOR]

Herein, we present a new magnetic iron oxide nanoparticle (MION) with a succinylated heparin monolayer coating, which exhibits the highest T 1 relaxivity at 7 T and the lowest r 2 / r 1 reported for any MION at these high-field conditions. While the recent proliferation of 7 T MRI instruments in hospitals worldwide has enabled widespread access to higher quality, more finely detailed, diagnostic imaging, clinically available contrast agents have not kept pace due to the general phenomenon of reduced efficacy of T 1 relaxation as magnetic field strength is increased. Development of new MION agents is one strategy to address this need, and to this end, we demonstrate the in vitro magnetic properties of the MIONs reported here to extend to in vivo applications, providing greatly increased contrast in tumor imaging in a murine xenograft subject at 7 T. While MION-based contrast agents can have side effects in clinical application, these are generally thought to be less than those of gadolinium-based agents and here are further reduced by the small size allowing direct glomerular filtration from the blood followed by renal-excretion. Finally, we show the succinylated heparin monolayer coating to provide class leading magnetic properties over a homologous series of particles with core size ranging from 2 to 18 nm and show the properties to be strongly related to the surface area. We suggest the increased porosity and hydrophilicity of the coating to increase water accessibility to the surface resulting in the increased magnetic properties.

Extraordinarily small (2.4 nm) cobalt ferrite nanoparticles (ESCIoNs) were synthesized by a one-pot thermal decomposition approach to study their potential as magnetic resonance imaging (MRI) contrast agents. Fine size control was achieved using oleylamine alone, and annular dark-field scanning transmission electron microscopy revealed highly crystalline cubic spinel particles with atomic resolution. Ligand exchange with dimercaptosuccinic acid rendered the particles stable in physiological conditions with a hydrodynamic diameter of 12 nm. The particles displayed superparamagnetic properties and a low r 2 / r 1 ratio suitable for a T 1 contrast agent. The particles were functionalized with bile acid, which improved biocompatibility by significant reduction of reactive oxygen species generation and is a first step toward liver-targeted T 1 MRI. Our study demonstrates the potential of ESCIoNs as T 1 MRI contrast agents.