Potential MRI Contrast Agents Research Articles

Noninvasive Diagnosis of Kidney Dysfunction Using a Small-Molecule Manganese-Based Magnetic Resonance Imaging Probe.

Contrast-enhanced magnetic resonance imaging (CE-MRI) is a promising approach for the diagnosis of kidney diseases. However, safety concerns, including nephrogenic systemic fibrosis, limit the administration of gadolinium (Gd)-based contrast agents (GBCAs) in patients who suffer from renal impairment. Meanwhile, nanomaterials meet biosafety concerns because of their long-term retention in the body. Herein, we propose a small-molecule manganese-based imaging probe Mn-PhDTA as an alternative to GBCAs to assess renal insufficiency for the first time. Mn-PhDTA was synthesized via a simple three-step reaction with a total yield of up to 33.6%, and a gram-scale synthesis can be realized. Mn-PhDTA has an r1 relaxivity of 2.72 mM-1 s-1 at 3.0 T and superior kinetic inertness over Gd-DTPA and Mn-EDTA with a dissociation time of 60 min in the presence of excess Zn2+. In vivo and in vitro experiments demonstrate their good stability and biocompatibility. In the unilateral ureteral obstruction rats, Mn-PhDTA provided significant MR signal enhancement, enabled distinguishing structure changes between the normal and damaged kidneys, and evaluated the renal function at different injured stages. Mn-PhDTA could act as a potential MRI contrast agent candidate for the replacement of GBCAs in the early detection of kidney dysfunction and analysis of kidney disease progression.

Gadolinium(III) complex formation with a β-cyclodextrin ligand: an XAS study of a potential MRI contrast agent.

In the search for improved and safer gadolinium-based magnetic resonance imaging (MRI) contrast agents, macrocyclic cyclodextrins (CDs) attract great interest. Our group previously synthesized a cyclodextrin-based ligand with 1,2,3-triazolmethyl residues conjugated to β-CD, called β-CD(A), which efficiently chelates Gd(III) ions. To probe the local structure around the Gd(III) ion in the 1:1 Gd(III): β-CD(A) complex in aqueous solution (pH 5.5), we used extended X-ray absorption fine structure (EXAFS) spectroscopy. Least-squares curve fitting of the Gd L3-edge EXAFS spectrum revealed 5 Gd-O (4 COO- and 1 H2O) and 4 Gd-N (from two imino and two 1,2,3-triazole groups) bonds around the Gd(III) ion with average distances 2.36 and 2.56 ± 0.02Å, respectively. A similar EXAFS spectrum was obtained from an aqueous solution of the clinically used MRI contrast agent Na[Gd(DOTA)(H2O)], also 9-coordinated in its first shell. Careful analysis revealed that the mean Gd-N distance is shorter in the Gd(III): β-CD(A) (1:1) complex, indicating stronger Gd-N bonding and stronger Gd(III) complex formation than with the DOTA4- ligand. This is consistent with the lower free Gd3+ concentration found previously for the Gd(III): β-CD(A) (1:1) complex than for the [Gd(DOTA)(H2O)]- complex, and shows its potential as an MRI probe. EXAFS spectroscopy revealed a similar Gd(III) 9-coordination although slightly stronger for a modified β-cyclodextrin: Gd(III) 1:1 complex, [Gd(LH4)]7-, in aqueous solution than for the clinically used MRI contrast agent Na[Gd(DOTA)(H2O)].

Development of Positively Charged Poly-L-Lysine Magnetic Nanoparticles as Potential MRI Contrast Agent.

A colloidal solution of magnetic nanoparticles (MNPs) modified with biocompatible positively charged poly-L-lysine (PLL) with an oleate (OL) layer employed as an initial coating was produced as a potential MRI contrast agent. The effect of various PLL/MNPs' mass ratios on the samples' hydrodynamic diameter, zeta potential, and isoelectric point (IEP) was studied by the dynamic light-scattering method. The optimal mass ratio for MNPs' surface coating was 0.5 (sample PLL0.5-OL-MNPs). The average hydrodynamic particle size in the sample of PLL0.5-OL-MNPs was 124.4 ± 1.4 nm, and in the PLL-unmodified nanoparticles, it was 60.9 ± 0.2 nm, indicating that the OL-MNPs' surface became covered by PLL. Next, the typical characteristics of the superparamagnetic behavior were observed in all samples. In addition, the decrease in saturation magnetizations from 66.9 Am2/kg for MNPs to 35.9 and 31.6 Am2/kg for sample OL-MNPs and PLL0.5-OL-MNPs also confirmed successful PLL adsorption. Moreover, we show that both OL-MNPs and PLL0.5-OL-MNPs exhibit excellent MRI relaxivity properties and a very high r2(*)/r1 ratio, which is very desirable in biomedical applications with required MRI contrast enhancement. The PLL coating itself appears to be the crucial factor in enhancing the relaxivity of MNPs in MRI relaxometry.

Comparison of Methemoglobin, Deoxyhemoglobin, and Ferrous Nitrosyl Hemoglobin as Potential MRI Contrast Agents.

Gadolinium-based contrast agents (GBCAs) are in widespread use to enhance magnetic resonance imaging for evaluating vascular pathology. However, safety concerns and limitations regarding the use of GBCAs has led to an increased interest in alternative contrast agents. Previously, methemoglobin (metHb) and oxygen-free hemoglobin (HHb) have been shown to increase the T1-weighted signal intensity of blood, which is associated with a decrease in the T1 parameter and an enhanced contrast of the image. Thus, a lower T1 value compared to the baseline value is favorable for imaging. However, it is unknown as to whether metHb or HHb would be a stronger and more appropriate contrast agent and to what extent the T1-weighted signal is affected by concentration. This study evaluated T1-weighted images of blood samples over a range of metHb and HHb concentrations, as well as ferrous nitrosyl hemoglobin (HbIINO) concentrations. Comparison of T1 values from a baseline value of ~ 1500ms showed that metHb is the strongest contrast agent (T1 ~ 950ms at 20% metHb) and that HHb is a relatively weak contrast agent (T1 ~ 1450ms at 20% HHb). This study showed for the first time that HbIINO can provide a contrast effect, although not as strong as metHb but stronger than HHb (T1 estimated as 1250ms at 20% HbIINO). With metHb providing a viable contrast between 10 and 20%, metHb has the potential to be a safe and effective contrast agent since it can be naturally converted back to hemoglobin.

PH‐Sensitive Polymethacrylates as Potential Contrast Agents in 19F MRI

Abstract19F MRI is a promising method of diagnosis that can complement the commonly used 1H MRI with gadolinium contrast agents. Copolymers containing fluoroorganic groups demonstrate many advantages as potential 19F MRI contrast agents. In this work, a series of copolymers based on 2,2,2‐trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFiPMA), 2‐(dimethylamino)ethyl methacrylate (DMAEMA), or 2‐hydroxyethyl methacrylate (HEMA) units are prepared using atom transfer radical polymerization. The highest S/N values in a 19F NMR spectra is achieved with a copolymer containing 15–25 wt% TFEMA or 18–22 wt% HFiPMA. Copolymers of HFiPMA show a strong effect of pH on T1 and T2 relaxation times while only T2 is significantly affected for the TFEMA copolymers. DFT calculations reveal that the phenomenon is most likely caused by the pH‐induced changes in the distance of fluoroorganic groups within a polymer chain.

Porous Silica Nanospheres with a Confined Mono(aquated) Mn(II)-Complex: A Potential T1-T2 Dual Contrast Agent for Magnetic Resonance Imaging.

Magnetic resonance imaging has emerged as an indispensable imaging modality for the early-stage diagnosis of many diseases. The imaging in the presence of a contrast agent is always advantageous, as it mitigates the low-sensitivity issue of the measurements and provides excellent contrast in the acquired images even in a short acquisition time. However, the stability and high relaxivity of the contrast agents remained a challenge. Here, molecules of a mononuclear, mono(aquated), thermodynamically stable [log KMnL = 14.80(7) and pMn = 8.97] Mn(II)-complex (1), based on a hexadentate pyridine-picolinate unit-containing ligand (H2PyDPA), were confined within a porous silica nanosphere in a noncovalent fashion to render a stable nanosystem, complex 1@SiO2NP. The entrapped complex 1 (complex 1@SiO2) exhibited r1 = 8.46 mM-1 s-1 and r2 = 33.15 mM-1 s-1 at pH = 7.4, 25 °C, and 1.41 T in N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid buffer. The values were about 2.9 times higher compared to the free (unentrapped)-complex 1 molecules. The synthesized complex 1@SiO2NP interacted significantly with albumin protein and consequently boosted both the relaxivity values to r1 = 24.76 mM-1 s-1 and r2 = 63.96 mM-1 s-1 at pH = 7.4, 37 °C, and 1.41 T. The kinetic inertness of the entrapped molecules was established by recognizing no appreciable change in the r1 value upon challenging complex 1@SiO2NP with 30 and 40 times excess of Zn(II) ions at pH 6 and 25 °C. The water molecule coordinated to the Mn(II) ion in complex 1@SiO2 was also impervious to the physiologically relevant anions (bicarbonate, biphosphate, and citrate) and pH of the medium. Thus, it ensured the availability of the inner-coordination site of complex 1 for the coordination of water molecules in the biological media. The concentration-dependent changes in image intensities in T1- and T2-weighted phantom images and uptake of the nanoparticles by the HeLa cell put forward the biocompatible complex 1@SiO2NP as a potential dual-mode MRI contrast agent, an alternative to Gd(III)-containing contrast agents.

Manganese-grafted detonation nanodiamond, a novel potential MRI contrast agent

Aiming to develop versatile MRI contrast agents, we report on preparation and magnetic resonance study of a novel nanomaterial - detonation nanodiamond (DND) with manganese ions directly grafted to its surface. The sample was prepared by reacting an aqueous nanodiamond suspension with an aqueous solution of manganese sulfate. We present clear evidence on chemical binding of Mn2+ ions to nanodiamond surface; ions interact with electron and nuclear spins of a diamond nanoparticle, thus accelerating spin-lattice relaxation. The distance between Mn2+ ion and diamond surface was estimated from the 13C NMR relaxation data. Comparison of the interaction of Mn ions with DND to that in the recently studied Gd-grafted DND suggests that Mn-DND will be a potential material as an MRI contrast agent.

Preparation of Graphene Oxide/Fe3O4 Nanocomposite as a Potential Magnetic Nanocarrier and MRI Contrast Agent

AbstractIn this paper, graphene oxide/ magnetite (GO/Fe3O4) nanocomposite was synthesized as a carrier and MRI contrast agent. X‐ray diffraction (XRD) indicated that the crystalline structure of Fe3O4 nanoparticles and Furrier transform infrared spectroscopy (FT‐IR) provided evidence for the presence of Fe3O4 and GO in the nanocomposite. The surface morphology of the nanocomposite was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The magnetic properties of the synthesized nanocomposite was studied by a vibrating sample magnetometer (VSM). The drug loading and encapsulation efficiency of the curcumin were 22 and 96 %, respectively. The comparison between drug release from GO/Fe3O4 in neutral and acidic pH was shown high release in neutral conditions. MTT results demonstrated that the GO/Fe3O4 nanocomposite illustrates considerable toxicity due to which cell viability decreased to lower than 50 % at 140 μg ml−1 concentration. The results showed that curcumin and curcumin loaded nanocomposite has a similar power of antioxidant activities. GO/Fe3O4 nanocomposite is a good magnetic resonance T2 contrast agent under the T2‐imaging sequences. The novelty of this study is the application of water‐dispersed GO/Fe3O4 with pH‐dependent release properties for designing a new colon drug delivery.

High Transverse Relaxivity and Anticancer Agent Loading/Release Characteristics of Porous Calcium Phosphate Coated Iron Oxide Nanoparticles

High relaxivity of MRI contrast agents leads to considerable contrast enhancement in the images and provides diagnostic accuracy. The purpose of the current study was to design a potential MRI contrast agent with a high relaxivity and investigate its curcumin loading/release property. To achieve this purpose, we synthesized the porous calcium phosphate coated iron oxide nanoparticles using a facile method and determined the physicochemical characteristics, cell compatibility effect, transverse relaxivity, and curcumin loading/release properties of the nanoparticles. The results indicated the spherical nanoparticles with a size of 10-20 nm. The nanoparticles demonstrated a superparamagnetic property and a high transverse relaxivity of 845.71 mM-1S-1. Although the porous calcium phosphate coated iron oxide nanoparticles were highly cytocompatible, the curcumin loaded nanoparticles showed a considerable effect on the bone marrow stem cells viability. In conclusion, the porous calcium phosphate coated iron oxide nanoparticles have the potential to introduce as a negative contrast agent of MRI with the ability of slow release of curcumin.

A Potential MRI Agent and an Anticancer Drug Encapsulated within CPMV Virus-Like Particles.

Virus nanoparticles have been extensively studied over the past decades for theranostics applications. Viruses are well-characterized, naturally occurring nanoparticles that can be produced in high quantity with a high degree of similarity in both structure and composition. The plant virus Cowpea Mosaic Virus (CPMV) has been innovatively used as a nanoscaffold. Utilization of the internal cavity of empty Virus-Like Particles (VLPs) for the inclusion of therapeutics within the capsid has opened many opportunities in drug delivery and imaging applications. The encapsidation of magnetic materials and anticancer drugs was achieved. SuperscriptCPMV denotes molecules attached to the external surface of CPMV and CPMVSubscript denotes molecules within the interior of the capsid. Here, the generation of novel VLPs incorporating iron-platinum nanoparticles TCPMVFePt and cisplatin (Cis) (TCPMVCis) is reported. TCPMVCis exhibited a cytotoxic IC50 of TCPMVCis on both A549 and MDA-MB-231 cell lines of 1.8 μM and 3.9 μM, respectively after 72 hours of incubation. The TCPMVFePt were prepared as potential MRI contrast agents. Cisplatin loaded VLP (TCPMVCis) is shown to enhance cisplatin cytotoxicity in cancer cell lines with its potency increased by 2.3-folds.

Large Carbon Clusters with Entrapped Gadolinium Atoms

Gadolinium metallofullerenes have long shown promise as potential MRI contrast agents. The ability to entrap up to three gadolinium atoms permits a high concentration of metal content per fullerene cage. The protective carbon cage prevents the escape of otherwise toxic free Gd ion. In this presentation, we will discuss purification strategies to isolate gadolinium clusters entrapped within larger carbon cages (C96-C120). We have recently isolated a series of fullertubes, which consist of a nanotube belt of carbons with fullerene endcaps. It is unknown if the entrapped Gd atoms are inside fullerene or fullertube cages.

A Ruthenium Nitrosyl-Functionalized Magnetic Nanoplatform with Near-Infrared Light-Controlled Nitric Oxide Delivery and Photothermal Effect for Enhanced Antitumor and Antibacterial Therapy.

Developing a spatiotemporal-controlled nitric oxide (NO) delivery nanoplatform is highly desirable for its biological applications as a tumor inhibitor and antibacterial agent. In this study, a novel multifunctional magnetic nanoplatform {Fe3O4@PDA@Ru-NO@FA} (1) was developed for the near-infrared (NIR) light-controlled release of NO in which a ruthenium nitrosyl (Ru-NO) donor and a folic acid (FA)-directing group were covalently functionalized onto Fe3O4@PDA. Nanoplatform 1 preferentially accumulated in folate receptor-overexpressing cancer cell lines and magnetic field-guided tumor tissue, instantly released NO, and simultaneously produced a prominent photothermal effect upon 808 nm NIR light irradiation, leading to remarkable in vitro and in vivo antitumor efficacy. When nanoplatform 1 was treated only once, the potential MRI contrast agent was sufficient to significantly inhibit or eliminate the tumor tissues in living mice, thus offering opportunities for future NO-involved multimodal cancer therapy. In addition, a NO delivery nanoplatform {Fe3O4@PDA@Ru-NO} was imbedded in the matrix of a chitosan (CS)-poly(vinyl alcohol) (PVA) material to develop a hybrid thermosensitive CS-PVA/NO hydrogel. The CS-PVA/NO hydrogels demonstrated mild (<150 mW cm-2) NIR light-controlled NO delivery and thus produced an efficient antibacterial effect for both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Therefore, these hydrogels have potential as antibacterial dressings for wound bacterial infection treatment.

Preparation of Bio‐Inspired Melanin Nanoplatforms Chelated with Manganese Ions as a Potential T1 MRI Contrast Agent

AbstractCommercial contrast agents demonstrated release risk of the toxic gadolinium ions, and designing of highly stable complexes of biogenic element such as Mn is challenging. In this contribution, Mn‐melanin nanoparticles have been prepared and reacted with m‐PEG. The effect of initial amount of Mn ions on the Mn absorption and its release by melanin nanoparticles (MNP) has been investigated. It has been found that MNP absorb and release more Mn ion by increasing the initial amount of Mn ions. It has been found that time and temperature has no significant effect on Mn absorption by MNP. It is found that the hydrodynamic size of MNP is in accordance with size of MNP which measured with TEM analysis (5.5±2 nm) and the effect of chain of m‐PEG and conformational alteration of MNP is responsible of hydrodynamic size variation. The zeta potential of MNP is decreased by PEGylation and reaction with Mn ions. MNP−Mn‐PEG demonstrated low toxicity up to 3.45 mg/mL after 24 h for human embryonic kidney cells. Finally, the r1 value of MNP−Mn‐PEG is 10 fold higher than Dotarem as the commercial MRI contrast agent which can be administrated at much lower doses to achieve similar contrast of Dotarem.

Hydrothermal Synthesis of an Ethiodol Based Ferrofluid as a Potential MRI Contrast Agent

In the present work, stable ferrofluids containing oleic acid capped magnetite nanoparticles were synthesized via low temperature hydrothermal method. The physical and chemical properties of the synthesized particles were studied using TEM, XRD, AFM, VSM and PCS techniques. Mean particles size of the samples was between 4.5 and 10 nanometers, depending on experimental conditions. Effect of precursor’s medium alkalinity was investigated on particle size. Cell culture experiments performed via MTT assay demonstrated that this product was biocompatible. In addition, cellular uptakes were investigated by Prussian blue staining and also measuring Fe concentration by inductively coupled plasma spectroscopy. Finally, the synthesized particles were dispersed in the Ethiodol and the obtained suspension was used as a potential MRI contrast agent. To the best of our knowledge, the mentioned procedure of using a non-aqueous based MRI contrast agent has been done for the first time in the present work and provides good capabilities as opposed to aqueous ones including reduced synthesis process time and increased magnetic properties of the obtained contrast agent.

Linear PVA-DTPA-Gd conjugate for magnetic resonance imaging.

In this study, we report the preparation and characterization of the PVA–DTPA–Gd conjugate as a potential MRI contrast agent (CA). The r1 value and the r2/r1 ratio were about 5.6 mM−1 s−1 and 1.31, respectively. In vitro toxicity studies not only demonstrated that the polymeric system possessed good biocompatibility, but also proved that the conjugate could be an attractive candidate for CA.

Reductive microenvironment responsive gadolinium-based polymers as potential safe MRI contrast agents.

Accumulation of nano-scale contrast agents in body tissues potentially induces adverse effects associated with free Gd(iii) ion release from the nano-scale system, such as nephrogenic systemic fibrosis and gadolinium deposition in the brain tissue. A novel formulation strategy was proposed herein for Gd-based macromolecular MRI contrast agents (Gd-mCAs), which may significantly reduce Gd(iii) retention but maintain sufficient imaging contrast. Biodegradable poly[N-(1,3-dihydroxypropyl)methacrylamide] copolymers (pDHPMA) were synthesized from N-(1,3-dihydroxypropyl)methacrylamide (DHPMA) as a monomer and enzyme-responsive short peptide (GFLG) as a chain transfer agent. Small molecular Gd-chelate (Gd-DOTA) was conjugated onto the copolymer backbone through a sulfide bond or a GSH-sensitive cleavable disulfide bond to produce two novel Gd-mCAs (pDHPMA-Cy5.5-DOTA-Gd or pDHPMA-Cy5.5-SS-DOTA-Gd) for tumor diagnosis. Their relaxivities were 10.49 and 10.24 mM-1 s-1 respectively, which were significantly higher than that of DTPA-Gd (3.97 mM-1 s-1). Compared with pDHPMA-Cy5.5-DOTA-Gd, pDHPMA-Cy5.5-SS-DOTA-Gd had a shorter Gd(iii) retention time but maintained a sufficient contrast efficacy. We have demonstrated that the conjugation of small molecular Gd-chelate to biodegradable macromolecular carriers through a ROX-sensitive biocleavable disulfide bond may be an efficient strategy for formulating safe biodegradable Gd-based pDHPMA copolymers as MRI contrast agents.

Aspects of structural order in 209Bi-containing particles for potential MRI contrast agents based on quadrupole enhanced relaxation

ABSTRACTQuadrupole relaxation enhancement (QRE) has been suggested as the key mechanism for a novel class of field-selective, potentially responsive magnetic resonance imaging contrast agents. In previous publications, QRE has been confirmed for solid compounds containing 209Bi as the quadrupolar nucleus (QN). For QRE to be effective in aqueous dispersions, several conditions must be met, i.e. high transition probability of the QN at the 1H Larmor frequency, water exchange with the bulk and comparatively slow motion of the Bi-carrying particles. In this paper, the potential influence of structural order within the compounds (‘crystallinity’) on QRE was studied by nuclear quadrupole resonance (NQR) spectroscopy in one crystalline and two amorphous preparations of Triphenylbismuth (BiPh3). The amorphous preparations comprised (1) a shock-frozen melt and (2) a granulate of polystyrene which contained homogeneously distributed BiPh3 after common dissolution in THF and subsequent evaporation of the solvent. In contrast to the crystalline powder which exhibits strong, narrow NQR peaks the amorphous preparations did not reveal any NQR signals above the noise floor. From these findings, we conclude that the amorphous state leads to a significant spectral peak broadening and that for efficient QRE in potential contrast agents structures with a high degree of order (near crystalline) are required.

Synthesis and Characterization of Rare‐Earth Orthoferrite LnFeO3 Nanoparticles for Bioimaging

A combination of sol–gel synthesis and thermal decomposition was developed for preparing nanosized, perovskite‐type LnFeO3 (Ln = Eu, Gd, Tb) powders. Perovskite‐type powders with crystalline particles of 100 nm average size, as determined by transmission electron microscopy (TEM), could be obtained after a thermal treatment at 800 °C. The perovskite nanoparticles (NPs) were further characterized by X‐ray powder diffraction and Mössbauer spectroscopy. These were in agreement with the pure perovskite LnFeO3 structure with the expected Zeeman sextet corresponding to a magnetically ordered phase. Magnetization measurements [M(H)] at 5 K and 300 K showed a behavior that is dominated by antiferromagnetic interactions and weak ferromagnetism in EuFeO3, while for Ln = Gd, Tb, they were dominated by the low ordering temperature Ln magnetic sublattice. The colloidal aqueous NPs suspensions exhibited no significant leaching of free Ln3+ ions. Their relaxivities define them as potential T2 MRI contrast agents for further biomedical applications. The NPs showed fast uptake and no cytotoxicity at concentrations below 62.5 µg/mL with respect to Hela cells.

Supramolecular assemblies based on amphiphilic Mn2+-complexes as high relaxivity MRI probes.

In the research field of MRI contrast agents (CAs), amphiphilic paramagnetic complexes are typically sought for the increased plasmatic half-life and high relaxivity values, but limited examples of amphiphilic Mn2+-based CAs have been reported to date. In this work the Mn2+-complexes of six original amphiphilic ligands (three EDTA-like ligands and three 1,4-DO2A derivatives) embodying one or two aliphatic chains were evaluated as potential MRI contrast agents and compared. Strong self-association into micelles resulted in a relaxivity (r1) enhancement (ca. 80% with respect to MnEDTA) as a consequence of the increased molecular tumbling rate of the supramolecular aggregate. In the case of bis-substituted systems the r1 gain is much higher due to the restricted local rotation of the chelates about the pendant aliphatic chains (r1 in the range 12.6-18.4 mM-1 s-1, 2-3 times higher than for the micelles obtained with single-chain EDTA systems). Furthermore, these amphiphilic chelates tightly bind to human serum albumin (HSA) with association constants KA in the range 104-105 M-1. The resulting supramolecular adducts achieve remarkable relaxivity values, in the range 50-60 mM-1 s-1 for the MnEDTA-like chelates and 27-30 mM-1 s-1 for the 1,4-DO2A-like systems (at 298 K and 20 MHz), thanks to their fast water exchange rate.

Highly Ordered Supramolecular Nanoassemblies of Paramagnetic Amphiphilic Chelates as Potential MRI Contrast Agents

Highly Ordered Supramolecular Nanoassemblies of Paramagnetic Amphiphilic Chelates as Potential MRI Contrast Agents