Enhancing Transversal Relaxation for Magnetite Nanoparticles in MR Imaging Using Gd³⁺-Chelated Mesoporous Silica Shells

Abstract

A new magnetic nanoparticle was synthesized in the form of Gd(3+)-chelated Fe(3)O(4)@SiO(2). The Fe(3)O(4) nanoparticle was octahedron-structured, was highly magnetic (∼94 emu/g), and was the core of an encapsulating mesoporous silica shell. DOTA-NHS molecules were anchored to the interior channels of the porous silica to chelate Gd(3+) ions. Because there were Gd(3+) ions within the silica shell, the transverse relaxivity increased 7-fold from 97 s(-1) mM(-1) of Fe(3)O(4) to 681 s(-1) mM(-1) of Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles with r(2)/r(1) = 486. The large transversal relaxivity of the Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles had an effective magnetic resonance imaging effect and clearly imaged lymph nodes. Physiological studies of liver, spleen, kidney, and lung tissue in mice infused with these new nanoparticles showed no damage and no cytotoxicity in Kupffer cells, which indicated that Gd(3+)-chelated Fe(3)O(4)@SiO(2) nanoparticles are biocompatible.

Controlled Synthesis of Uniform and Monodisperse Upconversion Core/Mesoporous Silica Shell Nanocomposites for Bimodal Imaging

“…The ultrasonic wave was introduced in the transfer and silica-coating process with an eye toward solving the aggregation problems. However, the temperature of the system reached 50 8C on account of the ultrasonic energy input, which would also result in the aggregation of composite nanoparticles (Figure 2e), as formerly observed by Yeh et al when synthesizing Fe 3 O 4 @mSiO 2 nanoparticles, [14] due to the accelerated hydrolyzation of TEOS at enhanced temperatures. To exclude the effect of temperature increase, the solution temperature was maintained at 25 8C during ultrasonication, and the TEM image (Figure 2f) reveals that monodisperse UCNP@mSiO 2 nanocomposites can be synthesized successfully by temperature control during ultrasonication.…”

“…Using this reported method, various functional cores were coated with a mesoporous silica shell. [10][11][12][13][14] However, the core-shell nanoparticles (NPs) synthesized according to the reported method were usually not as uniform and highly dispersed as desired. It is anticipated that there might be some key steps that should be adopted and carefully controlled to obtain uniform and monodisperse hydrophobic core@mesoporous silica shell nanocomposites.…”

“…The ultrasonic energy input effectively prevented the aggregation of nanoparticles during silica shell coating at the controlled temperature of 25 8C, thereby leading to the formation of monodisperse core-shell nanostructures with single UCNP cores that were uniformly coated by mesoporous silica shells. Compared with the method reported very recently, [14] in which the aggregates were removed by collecting the supernatants after centrifugation at 3500 rpm for 5 min, our method reported here can be used to produce monodisperse nanocomposite with high yield but without any post sieving.…”

Mesoporous Silica Nanoparticles: A Review

“…In this strategy, core and shell are fabricated in an inside to outside order. These specialized core-shell structures provide high magnetization up to 50 emug -1 [62,63]. This mesoporous silica shell act as a good drug carrier by providing sufficient surface area and pore volume to store and release the drug [1].…”

Dual-modal silica nanoprobes with surface enhanced Raman spectroscopic and fluorescent signals

“…Their unique optical and mechanical properties can afford them to be utilized as the efficient biomedical tools [1,2]. The functionalities invested to nanoparticles for the biological applications can be summarized like below; i) luminescence or fluorescence by quantum dots, luminophores or organic dyes [3][4][5], ii) surface enhanced Raman scattering (SERS) and near infrared (NIR) signals by novel metals [6][7][8][9], iii) magnetic resonance (MR) contrast enhancement by magnetic materials [10,11], and iv) driving-ability by also magnetic materials [12,13]. Many research groups have applied the specially functionalized nanoparticles for in vivo or in vitro experiments of labeling, targeting, imaging, sorting, etc.…”