Trimodal nanoparticle contrast-agent for MRI, CT and SPECT

Magnetic resonance imaging (MRI), Computed tomography (CT) and single photon emission computed tomography (SPECT) are the most widely used modalities for disease diagnosis. Nanoparticles have emerged as a promising class of contrast-agents for in vivo imaging. We present a novel design, of iron oxide-gold nanoparticle (IONP), radioisotope labeled, for trimodal MRI/CT/SPECT imaging.

Gold solution were prepared to form the gold shell for the IONPs (Fe₃O₄@Au). To enable radiolabeling and cell-tracking, the particles were coated by glucose and tetracarboxylic acid (DOTA). To evaluate feasibility as an MRI contrast-agents, solutions with different concentrations were scanned on a clinical 3T MRI scanner. Quantitative measurements were carried out using standard protocols to determine MR relaxation values in free-state. The feasibility of Fe₃O₄@Au nanoparticles as CT contrast-agents was assessed by a micro-CT scanner. Preliminary experiments on radiolabeling of the DOTA-glucose-coated Fe₃O₄@Au nanoparticles were carried out.

Uniformly distributed, spherical nanoparticles, composed of 8±2 nm iron-oxide core and 19nm thick gold shell were produced. MRI relaxation values decreased with increasing nanoparticle concentration, yielding clinically relevant values for three different common MRI contrasts. Greyscale quantification demonstrated a linear correlation between CT-contrast and the nanoparticles concentration. The radiochemical yield was higher than 98%, providing a single radioactive species with limited stability of up to 24h.

The new particle design showed efficient capabilities as CT/MRI imaging agent and high radiochemical yield, indicating a potential, hybrid material for multimodal SPECT/CT/MRI imaging.