A novel one-step synthesis of Gd3+-incorporated mesoporous SiO2 nanoparticles for use as an efficient MRI contrast agent

Molecular imaging has generated a demand for more sensitive contrast agents for magnetic resonance (MR) imaging. We synthesized, by a novel one-step method, Gd3+ incorporated mesoporous SiO2 nanoparticles, Gd2O3@SiO2, for use as an efficient contrast agent. The prepared nanoparticles were also coated with poly(lactic-co-glycolic acid) (PLGA). The size, morphology, composition and Brunauer-Emmett-Teller specific surface area of the nanoparticles were evaluated. The Gd2O3@SiO2 nanoparticles possess intragranular network morphology with a uniform size distribution and an average size of approximately 20-40 nm. The PLGA-coated nanoparticles were spherical or near-spherical in shape with a diameter of approximately 120 nm, a smooth surface, and neither aggregation nor adhesion tendencies. No free Gd ions were detected to dissociate from Gd2O3@SiO2 even up to the limit (< 0.03 mg/l) of the ICP equipment (IRIS Advantage). Our theoretical computation based on density functional theory (using DMol3, Materials Studio) revealed that the Gd2O3 molecules are fully absorbed on the interface of mesoporous SiO2 with a stable state of lower energy. Both Gd2O3@SiO2 and PLGA-coated Gd2O3@SiO2 samples have a larger T-1 relaxivitiy than commercial gadolinium diethylene triaminepentaacetate (Gd-DTPA). In vitro and in vivo MR images using the Gd2O3@SiO2 nanoparticles were observed with a 1.5 T clinical MR scanner and compared with the images using Gd-DTPA. The Gd2O3@SiO2 nanoparticles display a better magnetic property than commercial Gd-DTPA. In vivo MR imaging demonstrated that the nanoparticles were mainly distributed in the liver. Strong enhancement was also detected in nasopharyngeal carcinoma CNE-2 xenografted tumors. The Gd2O3@SiO2 nanoparticles are not only potential candidates for highly efficient contrast agents for MR imaging, but also might be developed into potent targeted probes for in vivo molecular imaging of cancer. Copyright (C) 2010 John Wiley & Sons, Ltd.