Mesoporous Europo‐Gadolinosilicate Nanoparticles as Bimodal Medical Imaging Agents and a Potential Theranostic Platform

Abstract

The mesoporous structure of sol-gel prepared gadolinium and europium doped silicate nanoparticles has been found to be highly dependent on the formulated composition, with synthesised samples displaying both disordered and hexagonally ordered mesoporous packing symmetry. The degree of pore ordering within the nanoparticles has a strong correlation with the total lanthanide (Gd(3+) and Eu(3+) ) concentration. The gadolinosilicates are excellent magnetic resonance imaging (MRI) longitudinal (T1 ) agents. The longitudinal relaxivity (r1 ) and transverse (r2 ) relaxivity, a measure of MRI contrast agent efficiency, were up to four times higher than the clinically employed Omniscan (gadodiamide); with r1 up to 20.6 s(-1) mM(-1) and r2 of 66.2 s(-1) mM(-1) compared to 5.53 and 4.64 s(-1) mM(-1) , respectively, for Omniscan. In addition, the europium content of all the samples studied is below the self-quenching limit, which results in a strong luminescence response from the nanoparticles on excitation at 250 nm. The Eu-Gd silicate nanoparticles act as bimodal imaging agents for MRI and luminescence. These mesoporous nanoparticles also have the potential to serve as encapsulation and controlled release matrices for pharmaceuticals. They are therefore a promising multimodal theranostic platform.

Tracking embryonic hematopoietic stem cells to the bone marrow: nanoparticle options to evaluate transplantation efficiency

“…In addition, the use of MSNs in imaging applications is an area of active research. In particular, MSNs are used to label and track cells through functionalization with fluorophores [ 11 , 29 – 34 ], ferromagnetic (iron-based) [ 35 – 37 ] and paramagnetic (gadolinium-based) materials [ 14 , 21 , 33 , 34 , 38 – 42 ] for magnetic resonance imaging (MRI), or electron-dense materials for computed tomography [ 43 – 46 ]. In turn, MSNs have promising utility in tracking stem cells upon their transplantation to define early trafficking patterns and to identify tissues eventually occupied by the transplanted stem cells.…”

“…In turn, MSNs have promising utility in tracking stem cells upon their transplantation to define early trafficking patterns and to identify tissues eventually occupied by the transplanted stem cells. Although ferrous contrast agents have been used in clinical MRI applications [ 35 – 37 , 47 , 48 ], gadolinium has favorable biocompatibility and, with seven unpaired electrons in its outer shell, a higher relaxivity, particularly for T1-weighted imaging [ 14 , 40 , 42 , 49 – 51 ]. Thus, it is the preferred material with which to develop innovative cell tracking schemes where high sensitivity is imperative.…”

Preparation and identification of multifunctional mesoporous silica nanoparticles for in vitro and in vivo dual-mode imaging, theranostics, and targeted tracking

“…In addition, another paramagnetic lanthanide ion, gadolinium (Gd 3þ ), is also used in our study because it is an excellent and well-recognized T1 contrast agent for magnetic resonance (MR) imaging. These two lanthanide ions (Eu 3þ and Gd 3þ ) can be added as dopants in the formation of silica nanoparticles [21].…”

Mesoporous gadolino–aluminosilicate nanoparticles as magnetic resonance imaging contrast agents

“…The hexagonal phase is robust compared to a similar gadolinium-europium silicate system we have observed previously. 20 Therein the hexagonal phase was observed only at the CTAB/TEOS ratio of 0.150 and 0.250, as opposed to all CTAB/TEOS ratio investigated herein.…”