Abstract
Several mesoporous silica nanoparticle (MSN) contrast agents have been synthesized using a co-condensation method to incorporate two different Gd3+ complexes at very high loadings (15.5–28.8 wt %). These MSN contrast agents, with an MCM-41 type pore structure, were characterized using a variety of methods including SEM and TEM, nitrogen adsorption measurements, thermogravimetric analysis (TGA), direct current plasma (DCP) spectroscopy, and powder X-ray diffraction (PXRD). The magnetic resonance (MR) relaxivities of these contrast agents were determined using a 3 T MR scanner. The r1 relaxivities of these nanoparticles range from 4.1 to 8.4 mM−1s−1 on a per Gd basis. Additionally, the MSN particles were functionalized with an organic fluorophore and cancer cell targeting peptide to allow for demonstration of both the optical and MR contrast enhancing capabilities in vitro.
Highlights
Contrast-enhanced magnetic resonance imaging (MRI) is a noninvasive diagnostic technique capable of providing high resolution anatomical images of soft tissue as well as giving quantitative assessment of disease pathogenesis [1,2,3]
Small molecule MRI contrast agents currently used in the clinic often cannot provide sufficient image contrast enhancement in early disease stages owing to their lack of sensitivity
We have previously developed a solid silica nanoparticle based MRI contrast agent, which consists of 37 nm particles coated with either a monolayer coating or a polymeric multilayer coating of Gd3+ chelates [11]
Summary
Contrast-enhanced magnetic resonance imaging (MRI) is a noninvasive diagnostic technique capable of providing high resolution anatomical images of soft tissue as well as giving quantitative assessment of disease pathogenesis [1,2,3]. We have previously developed a solid silica nanoparticle based MRI contrast agent, which consists of 37 nm particles coated with either a monolayer coating or a polymeric multilayer coating of Gd3+ chelates [11]. The results from these two systems revealed that the particles with a multilayer coating had reduced efficiency, or lower relaxivities, on a per Gd3+ basis. The co-condensation procedure affords MSNs with much higher loadings of Gd(III) chelates, but the r1 relaxivities of these nanoparticles appear to be smaller than previously reported MSNs with grafted Gd(III) chelates on a per Gd basis, presumably owing to the reduced accessibility of the Gd(III) chelates to the water molecules. A silyl-derived organic fluorophore and targeting agent were grafted to the surface to allow for target-specific optical and MR imaging of cancer cells
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