Quantification and excretion kinetics of a magnetic resonance imaging contrast agent by capillary electrophoresis-mass spectrometry

Trace determination of gadolinium by conductivity-based approach

A conductivity-based technique is developed for the determination of Gd3+ in the heavy water moderators of pressurized heavy water reactors (PHWRs). The method involves monitoring extremely small shifts in conductivity, in the order of few nS/cm, due to the continuous addition of a suitable complexing agent to Gd3+ in aqueous medium. The resulting plot gives two distinct regions with vastly differing slopes. Two multidentate ligands, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaaceticacid (DTPA), as complexing agents are compared. A high performing conductivity detector based on a new class of sensors called pulsating sensors that works entirely in the digital domain is deployed to monitor the conductivity shifts. Titration plots are studied in both H2O and D2O, and the observed difference between the plots in the two matrices is discussed in detail. Boron did not interfere in the analysis. The method was validated using the UV–vis spectrophotometric technique. The method is sensitive and rapid, as each analysis takes 3 min. The limit of detection in H2O and D2O are 1.27×10−7 mol/L and 5.1×10−7 mol/L, respectively. The precision in analysis lies between 1.9% and 5.3%. This method has important application in the nuclear industry for the routine analysis of gadolinium.

Gadolinium as an Emerging Microcontaminant in Water Resources: Threats and Opportunities

As a result of high doses of paramagnetic gadolinium (Gd) chelates administered in magnetic resonance imaging (MRI) exams, their unmetabolized excretion, and insufficient removal in wastewater treatment plants (WWTPs), large amounts of anthropogenic Gd (Gdanth) are released into surface water. The upward trend of gadolinium-based contrast agent (Gd-CA) administrations is expected to continue growing and consequently higher and higher anthropogenic Gd concentrations are annually recorded in water resources, which can pose a great threat to aquatic organisms and human beings. In addition, the feasibility of Gd retention in patients administered with Gd-CAs repeatedly, and even potentially fatal diseases, including nephrogenic systemic fibrosis (NSF), due to trace amounts of Gd have recently arisen severe health concerns. Thus, there is a need to investigate probable adverse health effects of currently marketed Gd-CAs meticulously and to modify the actual approach in using Gd contrast media in daily practice in order to minimize unknown possible health risks. Furthermore, the employment of enhanced wastewater treatment processes that are capable of removing the stable contrast agents, and the evaluation of the ecotoxicity of Gd chelates and human exposure to these emerging contaminants through dermal and ingestion pathways deserve more attention. On the other hand, point source releases of anthropogenic Gd into the aquatic environment presents the opportunity to assess surface water—groundwater interactions and trace the fate of wastewater plume as a proxy for the potential presence of other microcontaminants associated with treated wastewater in freshwater and marine systems.

Gadolinium-based contrast agents induce gadolinium deposits in cerebral vessel walls, while the neuropil is not affected: an autopsy study

Recent studies showed gadolinium depositions following serial administrations of gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging examinations in various parts of the brain with the dentate nucleus (DN) being most affected. Even though no clinical correlates of the deposits are known yet, an intensive debate developed if this might be harmful. The aim of the current study was to specify the gadolinium distribution in brain tissue of patients who received serial injections of GBCAs in the low-µm range and to explore any potential pathological tissue changes caused by gadolinium deposits. Thirteen autopsy cases-eight receiving GBCA administrations, five serving as controls-were identified and analyzed. For all patients, total gadolinium quantification after acidic digestion by means of inductively coupled plasma-mass spectrometry (ICP-MS) was performed. Six cases were utilized for the spatially resolved quantification of gadolinium within the cerebellum and the basal ganglia by means of high-resolution laser ablation (LA)-ICP-MS. Histopathological and immunohistochemical examinations were performed to determine tissue reactions. LA-ICP-MS revealed gadolinium depositions in the walls of small blood vessels of the DN in all GBCA exposed patients, while no gadolinium was found in the control group. Additionally, the detection of phosphorus and metals like copper, zinc and iron provides evidence that transmetalation reactions might have occurred. No significant pathological changes of the brain tissue in the vicinity of the DN with respect to micro-/astrogliosis and neuronal loss were found in any of the patients. This notably holds true even for a patient who died from nephrogenic systemic fibrosis exhibiting extremely high gadolinium concentrations within the DN. The findings show that gadolinium depositions in the brain are restricted to blood vessel walls, while the neuropil is spared and apparent cellular reactions are absent.

Spatially resolved quantification of gadolinium deposited in the brain of a patient treated with gadolinium-based contrast agents

Due to its paramagnetic properties resulting from seven unpaired f-electrons, Gd is frequently applied in magnetic resonance imaging examinations. Due to the acute toxicity of free Gd³⁺, ligand ions based on polyaminocarboxylic acids are used to create thermodynamically stable linear or macrocyclic complexes. The highly water soluble Gd-based contrast agents (GBCAs) are known to be excreted fast and unmetabolized, mostly via the kidneys. Nevertheless, recent studies showed that Gd traces persists not only in animal but also in human brain. Aim of this study was the development and application of an analytical method for the spatially resolved quantification of gadolinium traces in human brain thin sections of a patient treated with GBCAs. For this retrospective study different human brain regions were selected to analyze the distribution of gadolinium. An additional patient served as control sample, as no GBCA was administered. Deep-frozen brain thin sections were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and matrix-matched gelatin standards were prepared to quantify the gadolinium deposits via an external calibration. LA-ICP-MS analyses with high spatial resolution showed gadolinium deposits in different brain regions with highest concentrations above 800ngg^-1 more than two years after the last application of a GBCA. An excellent limit of quantification of 7ngg^-1, which is far below the limits of detection of MRI methods, could be achieved. The found concentrations confirm recent reports on gadolinium depositions in human brain, which were obtained without high spatial resolution. LA-ICP-MS provides limits of quantification, which are well suited to detect ultratrace amounts of gadolinium in human brain. Therefore, it provides valuable information on the distribution of gadolinium traces in the human brain even after single administration of GBCAs.

Anthropogenic gadolinium anomalies and rare earth elements in the water of Atibaia River and Anhumas Creek, Southeast Brazil

The concentrations of rare earth elements (REE), measured in water samples from Atibaia River and its tributary Anhumas Creek, Brazil, present excess of dissolved gadolinium. Such anthropogenic anomalies of Gd in water, already described in other parts of the world, result from the use of stable and soluble Gd chelates as contrast agents in magnetic resonance imaging. Atibaia River constitutes the main water supply of Campinas Metropolitan area, and its basin receives wastewater effluents. The REE concentrations in water samples were determined in 0.22-μm pore size filtered samples, without and after preconcentration by solid-phase extraction with bis-(2-ethyl-hexyl)-phosphate. This preconcentration method was unable to retain the anthropogenic Gd quantitatively. The probable reason is that the Gd chelates dissociate slowly in acidic media to produce the free ion that is retained by the phosphate ester. Strong correlations between Gd and constituents or parameters associated with effluents confirmed the source of most Gd in water samples as anthropogenic. The shale-normalized REE patterns of Atibaia River and Anhumas Creek water samples showed light and heavy REE enrichment trends, respectively. Also, positive Ce anomalies in many Atibaia River samples, as well as the strong correlations of the REE (except Gd) with terrigenous elements, imply that inorganic colloidal particles contributed to the REE measured values.

Capillary electrophoretic methods in the development of metal-based therapeutics and diagnostics: new methodology and applications

In recent years, capillary electrophoresis (CE) has matured to a standard method in medicinal inorganic chemistry. More and more steps of the drug discovery process are followed by CE. However, not only the number of applications has steadily increased but also the variety of used methodology has significantly broadened and, as compared to a few years ago, a wider scope of separation modes and hyphenated systems has been used. Herein, a summary of the newly utilized CE methods and their applications in metallodrug research in the timeframe 2006-2011 is presented, following related reviews from 2003 and 2007 (Electrophoresis, 2003, 24, 2023-2037; Electrophoresis 2007, 28, 3436-3446). Areas covered include impurity profiling, quality control of pharmaceutical formulations, lipophilicity estimation, interactions between metallodrugs and proteins or nucleotides, and characterization and also quantification of metabolites in biological matrices and real-world samples.

Detection of anthropogenic gadolinium in the Brisbane River plume in Moreton Bay, Queensland, Australia

Wastewater effluent is known to contain macro and micropollutants, which may be deleterious to environmental health. One such class of micropollutants is chelated gadolinium, which are used as MRI contrast agents. As these MRI contrast agents can be assumed to behave conservatively during estuarine mixing, it is possible to calculate how much wastewater is represented in any particular sample. In this study, the percentage contribution of wastewater at specific locations in Moreton Bay, Qld, were determined by calculating the additional anthropogenic gadolinium contribution to the total rare earth element concentrations. Wastewater contributions were measured at concentrations as low as 0.2%, demonstrating the applicability of this technique for wastewater effluent plume mapping.

Analysis of neurotrophins in human serum by immunoaffinity capillary electrophoresis (ICE) following traumatic head injury

Neurotrophins, including brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and beta-nerve growth factor (beta-NGF), play an active role in the development, maintenance and survival of cells of the central nervous system (CNS). Previous research has indicated that a decrease in concentrations of these neurotrophins is often associated with cell death and ultimately patient demise. However, much of the research conducted analyses of samples taken directly from the CNS, i.e., of samples that are not readily available in clinical trauma centers. In an attempt to obtain a method for evaluating neurotrophins in a more readily accessible matrix, i.e., serum, a precise and accurate immunoaffinity capillary electrophoresis (ICE) method was developed and applied to measure neurotrophins in serum from patients with various degrees of head injury. The five neurotrophins of interest were extracted and concentrated by specific immunochemically immobilized antibodies, bound directly to the capillary wall, and eluted and separated in approximately 10min. NT-3, BDNF, CNTF and beta-NGF showed a marked decrease in concentration as the severity of the head injury increased: mild versus severe: 91% decrease for NT-3; 93 % decrease for BDNF; 93 % decrease for CNTF; and a 87 % decrease for beta-NGF. This decrease in concentration is consistent with the neuro-protective roles that neurotrophins play in the maintenance and survival of neuronal cells. The results obtained by the ICE method were closely comparable with those generated by a commercially available ELISA method.