Gadolinium-conjugated TiO2-DNA oligonucleotide nanoconjugates show prolonged intracellular retention period and T1-weighted contrast enhancement in magnetic resonance images

Nanoconjugates composed of titanium dioxide (TiO2) nanoparticles, DNA oligonucleotides, and a gadolinium (Gd) contrast agent were synthesized for use in magnetic resonance imaging. Transfection of cultured cancer cells with these nanoconjugates showed them to be superior to the free contrast agent of the same formulation with regard to intracellular accumulation, retention, and subcellular localization. Our results have shown that 48 hours after treatment, the concentration of Gd in nanoconjugate-treated cells was 1000-fold higher than in cells treated with contrast agent alone. Consequently, T1-weighted contrast enhancements were observed in cells treated with nanoconjugates but not in cells treated by the contrast agent alone. This type of nanoconjugate with increased retention time, Gd accumulation, and intracellular delivery may find its use in Gd neutron-capture cancer therapy. (C) 2008 Elsevier Inc. All rights reserved.