Speciation of Al in human serum by convective-interaction media fast-monolithic chromatography with inductively coupled plasma mass spectrometric detection

Monolithic chromatography on conjoint liquid chromatography columns for speciation of platinum-based chemotherapeutics in serum of cancer patients

BACKGROUND

Monolithic chromatography using convective interaction media (CIM) disks or columns can be used in the separation step of speciation analysis. When different monolithic disks are placed in one housing, forming conjoint liquid chromatography (CLC) monolithic column, two-dimensional separation is achieved in a single chromatographic run.

METHODS

Here, we assembled low-pressure (maximum 50 bar) CLC monolithic column, which consists of two 0.34 mL shallow CIM monolithic disks and high-pressure CLC column (maximum 150 bar) from 0.1 mL analytical high performance short bed CIMac monolithic disks. Both the CLC columns constructed from affinity Protein G and weak anion exchange diethylamine (DEAE) disks, were applied for the speciation of cisplatin, oxaliplatin and carboplatin in spiked standard serum proteins, spiked human serum and serum of cancer patients. The analytical performances of the CLC columns used were evaluated by comparing their robustness, selectivity, repeatability and reproducibility. The separated serum proteins were detected on-line by ultraviolet (UV) and eluted Pt species by inductively coupled plasma mass spectrometry (ICP-MS). For accurate quantification of the separated Pt species (unbound Pt-based chemotherapeutic from species associated to transferrin (Tf), human serum albumin (HSA) and Immunoglobulin G (IgG)), post column isotope dilution (ID)-ICP-MS was used.

RESULTS

The data from analyses showed that both tested CLC monolithic columns gave statistically comparable results, with the low-pressure CLC column exhibiting better resolving power and robustness. It also enables more effective cleaning of monolithic disks and to analyse larger series of serum samples than the high-pressure CLC column. Analyses of serum samples of cancer patients treated with cisplatin or carboplatin showed that Pt-chemotherapeutics were bound preferentially to HSA (around 80%). The portion of unbound Pt in general did not exceed 2%, up to 5% of Pt was associated with Tf and approximately 20% with IgG. Column recoveries, calculated as a ratio between the sum of concentrations of Pt species eluted and concentration of total Pt in serum samples, were close to 100%.

CONCLUSIONS

Low-pressure CLC column exhibited greater potential than high-pressure CLC column, and can be thus recommended for its intended use in speciation analysis of metal-based biomolecules.

Impact of an Artificial Digestion Procedure on Aluminum-Containing Nanomaterials

Aluminum has gathered toxicological attention based on relevant human exposure and its suspected hazardous potential. Nanoparticles from food supplements or food contact materials may reach the human gastrointestinal tract. Here, we monitored the physicochemical fate of aluminum-containing nanoparticles and aluminum ions when passaging an in vitro model of the human gastrointestinal tract. Small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), ion beam microscopy (IBM), secondary ion beam mass spectrometry (TOF-SIMS), and inductively coupled plasma mass spectrometry (ICP-MS) in the single-particle mode were employed to characterize two aluminum-containing nanomaterials with different particle core materials (Al⁰, γAl₂O₃) and soluble AlCl₃. Particle size and shape remained unchanged in saliva, whereas strong agglomeration of both aluminum nanoparticle species was observed at low pH in gastric fluid together with an increased ion release. The levels of free aluminum ions decreased in intestinal fluid and the particles deagglomerated, thus liberating primary particles again. Dissolution of nanoparticles was limited and substantial changes of their shape and size were not detected. The amounts of particle-associated phosphorus, chlorine, potassium, and calcium increased in intestinal fluid, as compared to nanoparticles in standard dispersion. Interestingly, nanoparticles were found in the intestinal fluid after addition of ionic aluminum. We provide a comprehensive characterization of the fate of aluminum nanoparticles in simulated gastrointestinal fluids, demonstrating that orally ingested nanoparticles probably reach the intestinal epithelium. The balance between dissolution and de novo complex formation should be considered when evaluating nanotoxicological experiments.

TiO₂ nanoparticles functionalized monolithic capillary microextraction online coupled with inductively coupled plasma mass spectrometry for the analysis of Gd ion and Gd-based contrast agents in human urine

In this work, a novel method of TiO2 nanoparticles (NPs) functionalized monolithic capillary microextraction (CME) online coupling with inductively coupled plasma mass spectrometry (ICPMS) was developed for the sequential determination of Gd(3+) and Gd-based contrast agents in human urine samples. The monolithic capillary was prepared by embedding anatase TiO2 NPS in the poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EDMA) framework. The Gd(3+) and Gd-based contrast agents (such as gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) and Gd-DTPA-bismethylamide (Gd-DTPA-BMA)) display different adsorption behaviors on the prepared monolithic capillary which possesses the adsorption properties of both anatase TiO2 NPS and poly(MAA-EDMA) monolith. Under the optimized conditions, the limits of detection (LODs) were found to be 3.6, 3.2, and 4.5 ng L(-1) for Gd(3+), Gd-DTPA, and Gd-DTPA-BMA, respectively, which are the lowest up to date. The enrichment factor was 25-fold with the sample throughput of 5 h(-1). The proposed method was validated by the analysis of Gd(3+) and Gd-DTPA in the healthy human urine samples as well as Gd(3+) and Gd-DTPA-BMA in patient urine samples. It was found that only a small amount of the free Gd(3+) was released from Gd-DTPA-BMA, and accurate results could be obtained since no oxidation/reduction or subtraction is involved in this method. This method is simple, sensitive, and rapid and provides a very attractive nonchromatography strategy for the speciation of Gd(3+) and Gd-based contrast agents in urine samples.

Aluminum interaction with 2,3-diphosphoglyceric acid. A computational study

Favorable formation of aluminum–2,3-DPG complexes in a variety of forms: 1 : 1, 1 : 2 and ternary complexes with citrate.

Al3+ selective coumarin based reversible chemosensor: application in living cell imaging and as integrated molecular logic gate

The new coumarin based fluorescent ‘turn-on’ chemosensor (H₂L) efficiently detects Al³⁺ over other metal ions. It is efficient in detecting Al³⁺ in the intracellular region of HeLa cells and also exhibits an INHIBIT logic gate with Al³⁺ and EDTA as chemical inputs.

FRET based tri-color emissive rhodamine-pyrene conjugate as an Al3+ selective colorimetric and fluorescence sensor for living cell imaging

A rhodamine-pyrene hybrid molecule acts as a colorimetric and fluorimetric sensor for Al(3+) through time dependent PET-CHEF and FRET processes associated with tri-color emission. Intracellular Al(3+) has been visualized through time dependent blue-green-red emission. The lowest limit of detection for Al(3+) is 0.02 μM.

A novel method for speciation of Pt in human serum incubated with cisplatin, oxaliplatin and carboplatin by conjoint liquid chromatography on monolithic disks with UV and ICP-MS detection

Conjoint liquid chromatography (CLC) on monolithic convective interaction media (CIM) disks coupled on-line to UV and inductively coupled plasma mass spectrometry (ICP-MS) detectors was used for the first time in speciation analysis of Pt in human serum spiked with Pt-based chemotherapeutics. CIM Protein G and CIM DEAE disks were assembled together in a single housing forming a CLC monolithic column. Such a set-up allows rapid two-dimensional separation by affinity and ion-exchange (IE) modes to be carried out in a single chromatographic run. By applying isocratic elution with Tris-HCl-NaHCO3 buffer (pH 7.4) in the first minute, followed by gradient elution with 1 mol L(-1) NH4Cl (pH 7.4) in the next 9 min, immunoglobulins (IgG) were retained by the Protein G disk enabling subsequent separation of unbound Pt from Pt bound to transferrin (Tf) and albumin (HSA) on the CIM DEAE disk. Further elution with acetic acid (AcOH) in the next 3 min allowed separation of Pt associated with IgG. Separated Pt species were quantified by post-column isotope dilution-ICP-MS. Pt recovery on the CLC column was close to 100%. In comparison to commonly applied procedures that involve separation of protein peaks by size-exclusion chromatography (SEC) followed by IE separation of metal-based chemotherapeutic fractions bound to serum proteins, the CLC method developed is much faster and simpler. Its sensitivity (LOQs adequate for quantification of all separated Pt species, lower than 2.4 ng Pt mL(-1)), good selectivity and method repeatability (RSD±3%) enabled investigation of the kinetics of interaction of Pt-based chemotherapeutics with serum proteins and the distribution of Pt species in spiked human serum. Pt species present in spiked serum were bound preferentially to HSA. The proportion of Pt associated with IgG and Tf was lower than 13%. Cisplatin and especially oxaliplatin react rapidly with serum proteins, while carboplatin much less. The method developed may be reliably applied in preclinical and clinical studies of the kinetics of the interaction and distribution of different metallodrugs with proteins in blood serum.

Effects of a copper-deficient diet on the biochemistry, neural morphology and behavior of aged mice

Copper dyshomeostasis has been suggested as an aetiological risk factor for some neurodegenerative diseases, such as Alzheimer’s disease. However, the precise mechanism at the base of this involvement is still obscure. In this work, we show the effects of a copper-deficient diet in aged CD1 mice and the influence of such a diet on: a) the concentration of various metal ions (aluminium, copper, iron, calcium, zinc) in the main organs and in different brain areas; b) the alteration of metallothioneins I-II and tyrosine hydroxylase immunopositivity in the brain; c) behavioural tests (open field, pole, predatory aggression, and habituation/dishabituation smell tests). Our data suggested that the copper-deficiency was able to produce a sort of “domino effect” which altered the concentration of the other tested metal ions in the main organs as well as in the brain, without, however, significantly affecting the animal behaviour.

Constitutive and aluminium-induced patterns of phenolic compounds in two maize varieties differing in aluminium tolerance

Aluminium tolerance in maize is mainly due to more efficient Al exclusion. Nonetheless, even in tolerant varieties Al can gain access into the cells. Detoxification by binding to strong organic ligands should therefore play a role also in plants with high Al exclusion capacity. To test this hypothesis in this study the concentrations of soluble, free and bound, phenolics were analyzed in roots of two maize varieties differing in Al tolerance. Exposure for 24 h to 50 microM Al in nutrient solution strongly inhibited root elongation in the sensitive variety 16 x 36, but not in the Al-tolerant variety Cateto. Cateto accumulated about half the concentration of Al in roots than 16 x 36 (analysis performed after root desorption with citrate). Roots of Al-tolerant Cateto contained higher concentrations of caffeic acid, catechol and catechin than roots of the sensitive variety. Exposure to Al induced the accumulation of taxifolin in roots of both varieties. However, Al-tolerant Cateto accumulated about twice the concentration than Al-sensitive 16 x 36 of this pentahydroxyfavonol. The molar ratio for phenolics with catecholate groups to Al was about unity in roots of Cateto, while in those of 16 x 36 the ratio was ten times lower. Both the fact that these phenolics are strong ligands for Al and their high antioxidant and antiradical activity suggest that these compounds may provide protection against the Al fraction that is able to surpass the exclusion mechanisms operating in the tolerant maize variety.

Problems and progresses in speciation of Al in human serum: an overview

Aluminium (Al) is associated with many clinical disorders in renal patients. Al accumulation in brain has also been related to the neurodegenerative processes in Alzheimer's disease. In order to better understand Al transport in the human body, it is necessary to identify and quantify chemical species in which Al is present in body fluids and tissues. Among a variety of biological samples, Al speciation was the most frequently investigated in human serum. Improvements were made in the development of analytical techniques for the determination of the amount and composition of high molecular mass Al (HMM-Al) and low molecular mass Al (LMM-Al) species in human serum. However, due to the complex chemistry of Al in serum, its low total concentration and the high risk of contamination, speciation of Al in biological samples is still a difficult task for analytical chemists. In this work, problems related to speciation of Al in human serum are critically discussed. An overview of the progress that was made by the use of different analytical procedures, in order to propose analytical protocols for reliable speciation of Al in serum at low ng mL(-1) concentration range, is presented.

Applications of polymethacrylate-based monoliths in high-performance liquid chromatography

Monolithic columns were introduced in the early 1990s and have become increasingly popular as efficient stationary phases for most of the important chromatographic separation modes. Monoliths are functionally distinct from porous particle-based media in their reliance on convective mass transport. This makes resolution and capacity independent of flow rate. Monoliths also lack a void volume. This eliminates eddy dispersion and permits high-resolution separations with extremely short flow paths. The analytical value of these features is the subject of recent reviews. Nowadays, among other types of rigid macroporous monoliths, the polymethacrylate-based materials are the largest and most examined class of these sorbents. In this review, the applications of polymethacrylate-based monolithic columns are summarized for the separation, purification and analysis of low and high molecular mass compounds in the different HPLC formats, including micro- and large-scale HPLC modes.