Nano Archive

Paramagnetic silica-coated nanocrystals as an advanced MRI contrast agent

Gerion, Daniele and Herberg, Julie and Bok, Robert and Gjersing, Erica and Ramon, Erick and Maxwell, Robert and Kurhanewicz, John and Budinger, Thomas F. and Gray, Joe W. and Shuman, Marc A. and Chen, Fanqing Frank (2007) Paramagnetic silica-coated nanocrystals as an advanced MRI contrast agent. JOURNAL OF PHYSICAL CHEMISTRY C, 111 (34). pp. 12542-12551.

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We present a robust and general method for embedding nanoparticles, such as quantum dots (QD) or colloidal gold (Au) nanocrystals, into a highly water-soluble thin silica shell doped with paramagnetic gadolinium (Gd3+) ions without negatively impacting the optical properties of the QD or Au nanoparticle cores. The ultrathin silica shell has been covalently linked to Gd3+ ions chelator, tetraazacyclododecanetetraacetic acid (DOTA). The resulting complex has a diameter of 8 to 15 nm and is soluble in high ionic strength buffers at pH values ranging from approximately 4 to 11. For this system, nanoparticle concentrations exceed 50 AM, while most other nanoparticles might aggregate. In magnetic resonance imaging (MRI) experiments at clinical magnetic field strengths of 1.4 T (H-1 resonance frequency of 60 MHz), the gadolinium- DOTA (Gd-DOTA) attached to SiO2-coated QDs has a spin-lattice (T-1) particle relaxivity (r(1)) and a spin-spin (T-2) particle relaxivity (r(2)) of 1019 +/- 19 mM(-1)s(-1) and 2438 +/- 46 mM(-1) s(-1), respectively, for a 8-nm QD. The particle relaxivity has been correlated to the number of Gd3+ covalently linked to the silica shell. At 1.4 T, the Gd-DOTA ion relaxivities, r(1) and r(2), respectively, are 23 +/- 0.40 mM(-1)s(-1) and 54 +/- 1.0 mM(-1)s(-1). The sensitivity of our probes is in the 100-nM range for 8-10 nm particles and reaches 10 nM for particles approximately 15 nm in diameter. Preliminary dynamic contrast enhancement MRI experiments in mice revealed that silica-coated MRI probes are cleared from the renal system into the bladder with no observable affects on the health of the animal. This current approach may offer numerous advantages over other similar approaches, (1,2) including greater relaxivity and greater simplicity for the synthesis process of dual modality contrast agents that allow both MRI and optical detection as well as applicability to other nanoparticles.

Item Type:Article
Subjects:Material Science > Functional and hybrid materials
Biomedical Science > Nanobiotechnology
ID Code:3300
Deposited By:Farnush Anwar
Deposited On:15 Jan 2009 14:31
Last Modified:27 Jan 2009 16:00

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