Adding colour to ion-selective membranes.

An idea of using ion-exchanger salt containing optically active cations to prepare ion-selective membranes is proposed. Although the presence of an ion-exchanger in the composition of neutral ionophore based sensors is necessary, the choice of available salts for cation-selective sensors preparation, is usually limited to sodium or potassium compounds. In this work we propose application of an alternative salt, using a cation optically active both in absorption and emission mode as a mobile one.

Nanofiber Ion-Selective Membrane-Coated Carbon Paper All-Solid-State Sensors: One Stone, Two Birds.

Potentiometric sensors with nanostructural ion-selective membranes were prepared and tested. Electrospun nanofiber mats were applied in novel all-solid-state sensors, using carbon paper as an electronically conducting support. For the sake of simplicity, application of a solid contact layer was avoided, and redox-active impurities naturally present in the carbon paper have proven to be effective as ion-to-electron transducers.

Nanofiber-Supported Palladium Nanocubes-Toward Highly Active and Reusable Catalyst.

Electrospun nanofibers were used to support palladium nanocubes, resulting in a highly active, stable, and reusable catalyst. The system proposed herein offers significant advantages compared to catalysts in the form of nanoparticles suspension. The porous, solvent permeable structure of the nanofiber mat ensures uniform and stable time distribution of palladium nanoparticles; preventing coalescence and allowing multiple use of the catalyst.

Mice, rats, and guinea pigs differ in FMOs expression and tissue concentration of TMAO, a gut bacteria-derived biomarker of cardiovascular and metabolic diseases.

Introduction: Increased plasma trimethylamine oxide (TMAO) is observed in cardiovascular and metabolic diseases, originating from the gut microbiota product, trimethylamine (TMA), via flavin-containing monooxygenases (FMOs)-dependent oxidation. Numerous studies have investigated the association between plasma TMAO and various pathologies, yet limited knowledge exists regarding tissue concentrations of TMAO, TMAO precursors, and interspecies variability.

Methods: Chromatography coupled with mass spectrometry was employed to evaluate tissue concentrations of TMAO and its precursors in adult male mice, rats, and guinea pigs.

Hypertensive rats show increased renal excretion and decreased tissue concentrations of glycine betaine, a protective osmolyte with diuretic properties.

Hypertension leads to water-electrolyte disturbances and end-organ damage. Betaine is an osmolyte protecting cells against electrolyte imbalance and osmotic stress, particularly in the kidneys. This study aimed to evaluate tissue levels and hemodynamic and renal effects of betaine in normotensive and hypertensive rats.

Finding a perfect match of ion-exchanger and plasticizer for ion-selective sensors.

Application of neutral ionophore based ion-selective sensors requires presence of ion-exchanger in the receptor phase, silently assuming that it is not only soluble but also dissociates to ions in the applied plasticizer. Although for typically applied ion-selective membrane constituents (plasticizers - ion-exchanger pairs) dissociation of ion-exchangers to ions is proven by theoretical (or close to) performance of resulting sensors, search for alternative plasticizers or ion-exchangers requires a method allowing estimation of the match of properties of involved compounds. In this work we propose a simple optical approach allowing estimation of ion-exchanger interactions with plasticizer.

Mice, Rats and Guinea Pigs Exhibit Significant Variations in the Plasma, Urine and Tissue Levels of Taurine, Betaine, Sarcosine and Other Osmolyte-Active Amino Acids.

Background: Osmolytes are naturally occurring compounds that protect cells from osmotic stress in high-osmolarity tissues, such as the kidney medulla. Some amino acids, including taurine, betaine, glycine, alanine, and sarcosine, are known to act as osmolytes. This study aimed to establish the levels of these amino acids in body fluids and tissues of laboratory animals used as models for human diseases in biomedical research.

Trimethylamine, a gut bacteria metabolite and air pollutant, increases blood pressure and markers of kidney damage including proteinuria and KIM-1 in rats.

Background: Trimethylamine oxide (TMAO) is a biomarker in cardiovascular and renal diseases. TMAO originates from the oxidation of trimethylamine (TMA), a product of gut microbiota and manufacturing industries-derived pollutant, by flavin monooxygenases (FMOs). The effect of chronic exposure to TMA on cardiovascular and renal systems is undetermined.

Ion-selective membrane plasticizer leakage in all-solid-state electrodes - an unobvious way to improve potential reading stability in time.

The effect of leakage of the plasticizer from the ion-selective membrane into the ion-to-electron transducer of all-solid-state potentiometric sensors is considered for the first time. The plasticizer can be transferred to the transducer phase, either during ion-selective membrane application or later; in both cases, its presence can affect the performance of the sensors. Clearly, this effect is most pronounced if the transducer is dispersible in the plasticizer.

Bypassed ion-selective electrodes - self-powered polarization for tailoring of sensor performance.

Potentiometric ion-selective sensors are attractive analytical tools as they have simple apparatus and facile use; however their analytical parameters cannot be easily tuned. To tailor the performance of these sensors, application of instrumental control - electrochemical trigger - is usually required. The proposed approach offers a self-powered instrument-free alternative.

3D-Drawn Supports for Ion-Selective Electrodes.

A new concept of easy to make, potentially disposable potentiometric sensors is presented. A thermoprocessable carbon black-loaded, electronically conducting, polylactide polymer composite was used to prepare substrate electrodes of user's defined shape/arrangement applying a 3D pen in a hot melt process. Covering of the carbon black-loaded polylactide 3D-drawn substrate electrode with a PVC-based ion-selective membrane cocktail results in spontaneous formation of a zip-lock structure with a large contact area.

Dual Sensitivity─Potentiometric and Fluorimetric─Ion-Selective Membranes.

Classical application of ion-selective membranes is limited to either electrochemical or optical experiments. Herein, the proposed ion-selective membrane system can be used in both modes; each of them offering competitive analytical parameters: high selectivity and linear dependence of the signal on logarithm of analyte concentration, high potential stability in potentiometric mode, or applicability for alkaline solutions in optical mode. Incorporation of analyte ions into the membrane results in potentiometric signals, as in a classical system.

Cubosome Based Ion-Selective Optodes-Toward Tunable Biocompatible Sensors.

We report here on a new generation of optical ion-selective sensors benefiting from cubosomes or hexosomes-nanostructural lipid liquid phase. Cubosome as well as hexosome optodes offer biocompatibility, self-assembly preparation, high stability in solution, and unique, tunable analytical performance. The temperature trigger reversibly changes the lipid nanoparticle internal structure-changing analyte access to the bulk of the probe and ultimately affecting the response pattern.

Emission Intensity Readout of Ion-Selective Electrodes Operating under an Electrochemical Trigger.

We report for the first time on in situ transduction of electrochemical responses of ion-selective electrodes, operating under non-zero-current conditions, to emission change signals. The proposed novel-type PVC-based membrane comprises a dispersed redox and emission active ion-to-electron transducer. The electrochemical trigger applied induces a redox process of the transducer, inducing ion exchange between the membrane and the solution, resulting also in change of its emission spectrum.

Induced ion-pair formation/ de-aggregation of rhodamine B octadecyl ester for anion optical sensing: Towards ibuprofen selective optical sensors.

A novel approach is explored to result in anion selective nanostructural optodes, that do not require the presence of selective ionophore. The sensing principle proposed is based on interactions of polarity sensitive dye with anions, leading to change of the chromophore group environment, resulting in increase of emission for increase of analyte concentration. To induce interactions of the analyte with the dye precise matching of properties of analyte and receptor is required.

Insights into Primary Ion Exchange between Ion-Selective Membranes and Solution. From Altering Natural Isotope Ratios to Isotope Dilution Inductively Coupled Plasma Mass Spectrometry Studies.

Although ion-selective electrodes have been routinely used for decades now, there are still gaps in experimental evidence regarding how these sensors operate. This especially applies to the exchange of primary ions occurring for systems already containing analyte ions from the pretreatment step. Herein, for the first time, we present an insight into this process looking at the effect of altered ratios of naturally occurring analyte isotopes and achieving isotopic equilibrium.

Unintended Changes of Ion-Selective Membranes Composition-Origin and Effect on Analytical Performance.

Ion-selective membranes, as used in potentiometric sensors, are mixtures of a few important constituents in a carefully balanced proportion. The changes of composition of the ion-selective membrane, both qualitative and quantitative, affect the analytical performance of sensors. Different constructions and materials applied to improve sensors result in specific conditions of membrane formation, in consequence, potentially can result in uncontrolled modification of the membrane composition.

Ion-selective reversing aggregation-caused quenching - Maximizing optodes signal stability.

An alternative optical signal transduction mechanism for ion-selective optodes is proposed. The nanostructural sensors benefit from ion-selective reversing aggregation caused quenching yielding turn-on, bright and highly stable optical signals. Selective incorporation of analyte results in transformation of the polymer dye from aggregate to a micelle structure, affecting spatial arrangement of chromophore groups in the nanostructure.

A potentiometric sensor based on modified electrospun PVDF nanofibers - towards 2D ion-selective membranes.

Core-shell modified nanofiber mats were used as ion-selective membranes for the first time. Keeping the overall macroscopic size of the sensing element the same as for classical plasticized poly(vinyl chloride) membranes, herein the proposed nanofiber based systems resulted in ultrathin (<10 nm) recognition layers with the total area nearly 3 orders of magnitude larger and the surface to volume ratio close to 7.5 × 10.

TMAO, a seafood-derived molecule, produces diuresis and reduces mortality in heart failure rats.

Trimethylamine-oxide (TMAO) is present in seafood which is considered to be beneficial for health. Deep-water animals accumulate TMAO to protect proteins, such as lactate dehydrogenase (LDH), against hydrostatic pressure stress (HPS). We hypothesized that TMAO exerts beneficial effects on the circulatory system and protects cardiac LDH exposed to HPS produced by the contracting heart.

Quantifying plasticizer leakage from ion-selective membranes - a nanosponge approach.

The spontaneous process of release of plasticizers from membranes typically used in ion-selective sensors is an effect which limits the lifetime of sensors and comes with a risk of safety hazards. We use a nanosponge approach to look at the magnitude of this problem, quantifying the resulting contents of the plasticizer in solution. This novel method takes advantage of the spontaneous partition of the plasticizer (released and present in solution) into nanoparticles loaded with a solvatochromic dye.

Tailoring polythiophene cation-selective optodes for wide pH range sensing.

A challenge in turn-on mode operating optodes application is elimination of pH sensitivity. The polyoctylthiophene based optodes response mechanism is not involving hydrogen ions exchange, thus paves the way for optodes applicable for sensing in wide pH range. We report on nanoptodes that can be used both in alkaline and in acidic pH range inaccessible for classical systems using pH sensitive dyes as transducers.

Hydrogen sulfide formation in experimental model of acute pancreatitis.

Acute pancreatitis (AP) is a disease defined as acute or chronic inflammatory process of the pancreas characterized by premature activation of digestive enzymes within the pancreatic acinar cells and causing pancreatic auto-digestion. In mammalian tissues, H2S is synthesized endogenously from L-cysteine in regulated enzymatic pathways catalyzed by pyridoxal phosphate-dependent enzymes: cystathionine beta - synthase (CBS), gamma - cystathionase (CTH) and cysteine aminotransferase (CAT) coupled with 3-mercaptopyruvate sulfurtransferase (MPST). In the mitochondria, hydrogen sulfide is oxidized to sulfite, which is then converted to thiosulfate (sulfane sulfur-containing compound) by thiosulfate sulfurtransferase (rhodanese; TST).

Self-Powered Cascade Bipolar Electrodes with Fluorimetric Readout.

Bipolar electrodes working in a self-powered mode are a basis for the development of easy to use electrochemical-optical sensors, these systems are very promising due to their simplicity and no need of external polarization. However, the self-powered mode can be used only in cases when the redox potential difference of reactions occurring at opposite poles of the electrode is sufficiently high. To overcome this limitation, we propose the development of a system working spontaneously, but involving two bipolar electrodes, forming a cascade system.

Electrospun nanofiber supported optodes: scaling down the receptor layer thickness to nanometers - towards 2D optodes.

A novel type of optode sensor is proposed using electrospun nanofibers as the supporting inert material. The proposed arrangement offers the possibility of a significant extension of the surface area of the probe while also minimizing the thickness of the receptor layer. This novel, close to 2D, optode configuration results in a sensor free from limitations related to analyte transport in the receptor phase.