[Gadolinium-loaded nanoparticle as a novel molecular imaging contrast agent for magnetic resonance imaging].

Objective: To synthesize a novel gadolinium-loaded nanoparticle as a molecular imaging contrast agent for magnetic resonance imaging.

Methods: Gadolinium ion was incorporated within a silica nanoparticle. The size of this nanosized particle was determined by using transmission electron microscope. The spin-echo (SE) images of nine nanoparticle dilutions in vitro were obtained from a 1.5 T clinical scanner, compared with gadolinium diethylene triaminepenta acetate (Gd-DTPA). In vivo distribution of nanoparticle in Balb/c nude mice and Balb/c nude mice with nasopharyngeal carcinoma (NPC) xenografted CNE-2 tumors was studied at MR imaging, 30 sec, 5 min, 30 min, 1 h, 2 h, 4 h, and 24 h after intravenous administration.

Results: The gadolinium-loaded nanoparticle was short rod-shaped, and approximately 30 to 40 nm in diameter. The value of longitudinal relaxativity (r(1)) of gadolinium nanoparticle was much higher than that of Gd-DTPA. Thirty minutes after injection the gadolinium nanoparticle, the signal intensities of liver, kidney and xenografted tumor increased from 226 +/- 10, 283 +/- 7 and 195 +/- 5 to 352 +/- 12, 328 +/- 10 and 245 +/- 7, respectively. The dynamic MRI scanning showed that gadolinium nanoparticles were mainly distributed in liver after intravenous administration. Strong enhancement was also detected in CNE-2 xenografted tumors.

Conclusion: A new gadolinium-loaded nanoparticle with high relaxativity was synthesized successfully, and might serve as a carrier for magnetic resonance molecular imaging.