Engineered contrast agents in a single structure forT₁–T₂dual magnetic resonance imaging

Abstract

The development of contrast agents (CAs) for Magnetic Resonance Imaging (MRI) with T1-T2 dual-mode relaxivity requires the accurate assembly of T1 and T2 magnetic centers in a single structure. In this context, we have synthesized a novel hybrid material by monitoring the formation of Prussian Blue analogue Gd(H2O)4[Fe(CN)6] nanoparticles with tailored shape (from nanocrosses to nanorods) and size, and further protection with a thin and homogeneous silica coating through hydrolysis and polymerization of silicate at neutral pH. The resulting Gd(H2O)4[Fe(CN)6]@SiO2 magnetic nanoparticles are very stable in biological fluids. Interestingly, this combination of Gd and Fe magnetic centers closely packed in the crystalline network promotes a magnetic synergistic effect, which results in significant improvement of longitudinal relaxivity with regards to soluble Gd3+ chelates, whilst keeping the high transversal relaxivity inherent to the iron component. As a consequence, this material shows excellent activity as MRI CA, improving positive and negative contrasts in T1- and T2-weighted MR images, both in in vitro (e.g., phantom) and in vivo (e.g., Sprague-Dawley rats) models. In addition, this hybrid shows a high biosafety profile and has strong ability to incorporate organic molecules on the surface with variable functionality, displaying great potential for further clinical application.

Dual T1/T2 Nanoscale Coordination Polymers as Novel Contrast Agents for MRI: A Preclinical Study for Brain Tumor

“…This radiation-free technique enables the coding of nuclear magnetization into 2D/3D images, being the most used tool in clinical diagnosis. The signal intensity of proton-based MRI ( 1 H-MRI) depends on a combination of factors: proton density, longitudinal ( T 1 ) and transversal ( T 2 ) relaxivity times and the cell microenvironment. , However, the intrinsic contrast provided by the combination of these factors and the biological changes due to a disease are not enough for obtaining accurate and sensitive diagnosis. For these reasons, the use of contrast agents (CAs) in MRI diagnosis is needed in order to improve image resolution due to their selective accumulation in the Region-Of-Interest (ROI).…”

Amino modified metal-organic frameworks as pH-responsive nanoplatforms for safe delivery of camptothecin

“…whereas elemental analysis revealed an amino group concentration of 3.6 mmol g -1 , very close to the stoichiometric calculation (3.8 mmol g -1 ). In the case of M2-NH2 material we introduced acetic acid in the synthetic process to modulate crystal growth rate, as already shown for other MOF structures [12,32], obtaining monodispersed nanoparticles of about 117 ± 33 nm average diameter, as determined by TEM measurements (Fig. 1b).…”

“…They take advantage of their lack of toxicity, easy size-reduction to the nanoscale and the intrinsic relative lability of metal ligand bonds, which favors their biodegradability [10]. Moreover, they have been shown to be very efficient as contrast agents in magnetic resonance imaging, computed tomography and optical imaging [11,12], as sensitizing agents in photothermal [13] and photodynamic therapy [14], and as drug delivery systems (DDSs) [11,[15][16][17]. In this context, MOFs belonging to the family of MILs (Materials of Institute Lavoisier), which are formed by carboxylate ligands and iron (III) as a non-toxic cation, have shown enormous potential in the loading and safe release of large drug quantities [18][19][20].…”

Nanoheterostructures based on nanosized Prussian blue and its Analogues: Design, properties and applications

“…On the other hand, in the case of Gd[Fe(CN)6]4H2O@SiO2 nanoparticles, due to the very high sensibility of the latter to basic pH, inducing the formation of Gd(OH)3, the nanoparticles were coated with a thin silica layer at neutral pH by adding (3-cyanopropyl)trimethoxysilane (CPTMS), tetramethyl orthosilicate (TMOS) and in the presence of a functional mimics of the protein silicatein , triethylamine (TEA) as the catalyst. [259] In that case, the formation of an amorphous, non-porous shell of around 10 -12 nm was noted. In all cases, a well-formed silica shell was formed on the surface of PB(A) nanoparticles, as attested by the TEM images shown in Figure 23.…”

“…The design of PB(A)s core@silica shell nano-objects are usually made by using a two-step procedure consisting first in the synthesis of pristine coordination polymer nanoparticles by the usual self-assembly of cyanometallate and metal salts precursors' reaction and then by using a classical sol-gel process to form a homogenous porous silica shell on the surface. To this purpose, five examples of PB(A) core@silica shell nanoparticles with different core composition, including Mn3[Co(CN)6]2, [254] PB, [255], [256], [257] [258] and Gd [Fe(CN)6].4H2O [259] with different core geometries were reported. The employed sol-gel methods and conditions are summarized in Figure 22.…”