The impact of gut bacteria producing long chain homologs of vitamin K2 on colorectal carcinogenesis.

Colorectal cancer (CRC) is one of the foremost causes of cancer-related deaths. Lately, a close connection between the course of CRC and the intestinal microbiota has been revealed. Vitamin K2 (VK2) is a bacterially derived compound that plays a crucial role in the human body. Its significant anti-cancer properties may result, inter alia, from a quinone ring possessing a specific chemical structure found in many chemotherapeutics. VK2 can be supplied to our body exogenously, i.e., through dietary supplements or fermented food (e.g., yellow cheese, fermented soybeans -Natto), and endogenously, i.e., through the production of bacteria that constantly colonize the human microbiome of the large intestine.This paper focuses on endogenous K2 synthesized by the most active members of the human gut microbiome. This analysis tested 86 intestinally derived bacterial strains, among which the largest VK2 producers (Lactobacillus, Bifidobacterium, Bacillus) were selected. Moreover, based on the chosen VK2-MK4 homolog, the potential of VK2 penetration into Caco-2 cells in an aqueous environment without the coexistence of fats, pancreatic enzymes, or bile salts has been displayed. The influence of three VK2 homologs: VK2-MK4, VK2-MK7 and VK2-MK9 on apoptosis and necrosis of Caco-2 cells was tested proving the lack of their harmful effects on the tested cells. Moreover, the unique role of long-chain homologs (VK2-MK9 and VK2-MK7) in inhibiting the secretion of pro-inflammatory cytokines such as IL-8 (for Caco-2 tissue) and IL-6 and TNFα (for RAW 264.7) has been documented.

Electrochemical sensing platform based on screen-printed carbon electrode modified with plasma polymerized acrylonitrile nanofilms for determination of bupropion.

A original electrochemical sensing platform, based on screen-printed electrodes modification with plasma polymerized acrylonitrile (pp-AN) nanofilms is proposed. For that purpose, plasma-enhanced chemical vapor deposition (PECVD) process was conducted in a parallel plate (13.56 MHz) plasma reactor for 2 min with discharge power of 10 W. The surface topography and electrochemical properties of prepared sensors were investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The electrochemical characteristics of pp-AN/SPCE and pp-AN/SPAuE sensors was investigated for model redox pair [Fe(CN)6]4-/3-. Conducted research confirmed the excellent chemical stability, durability, wide potential window, high signal-to-noise (S/N) ratio, and, most importantly, the ability to standardize the sensors. The pp-AN/SPCE sensor was applied to the determination of bupropion, an antidepressant drug whose intake has increased dramatically during the COVID-19 pandemic. The voltammetric response of pp-AN/SPCE for BUP was linear in two concentration ranges of 0.63-10.0 and 10.0-50.0 µmol L-1, with a detection limit of 0.21 µmol L-1. Satisfactory recoveries (96.2-102%) and good precision (RSD below 4.1%) obtained for environmental and biological samples confirmed the usefulness of the sensor for the analysis of various kinds of samples.

Electrochemical sensing platform based on Zeolite/Graphite/Dimethylglyoxime nanocomposite for highly selective and ultrasensitive determination of nickel.

In this work, the fabrication and analytical application of a novel, unique, mercury-free, and user-friendly voltammetric sensor of Ni(II) based on glassy carbon electrode (GCE) modified with zeolite(MOR)/graphite(G)/dimethylglyoxime(DMG) composite (MOR/G/DMG-GCE) and the voltammetric procedure for highly selective, ultra-trace determination of nickel ions were reported for the first time. Deposition of a thin layer of the chemically active MOR/G/DMG nanocomposite enables the selective and effective accumulation of Ni(II) ions in the form of the DMG-Ni(II) complex. In 0.1 mol L-1 ammonia buffer (pH 9.0), the MOR/G/DMG-GCE exhibited linear response in the Ni(II) ions concentration range of 0.86 - 19.61 µg L-1 and 0.57 - 15.75 µg L-1, for the accumulation time of 30 s and 60 s, respectively. For 60 s of accumulation time, the limit of detection (S/N = 3) was 0.18 µg L-1 (3.04 nM), and sensitivity of 0.202 µA L µg-1 was achieved. The developed protocol was validated by the analysis of wastewater certified reference materials. Its practical usefulness was confirmed by the determination of nickel released from metallic jewelry submerged in artificial sweat and stainless steel pot during water boiling. The obtained results were verified by electrothermal atomic absorption spectroscopy as a reference method.

Deep learning assisted distinguishing of honey seasonal changes using quadruple voltammetric electrodes.

The work presents innovative quadruple disk iridium, platinum, and iridium-platinum voltammetric electrodes with a special design, dedicated to the testing of samples with a complex organic composition. Noble metal wires are tightened in one silver rod, and therefore each of them acts as a single sensor. It was demonstrated that the signals of the iridium-platinum sensor combine the electrode responses constructed from one metal, which increases the possibilities and range of applications of this sensor, and it can be used as an electronic tongue. These single and combined noble metal electrodes were successfully verified to profile the seasonal variability of honey collected from an apiary in Malopolska (voivodeship in Poland). Data obtained by the differential pulse voltammetry, according to the principles of green chemistry, without using any reagents, were interpreted by principal component analysis, preceded by the optimized variable selection procedure. The best results in distinguishing 12 honeys were obtained using a multimetallic electrode. The classification model calculated using deep convolutional neural networks indicated the proper belonging of honeys to the groups with 100% accuracy for the training and validation set. The proposed solution proved that noble metals quadruple disk electrodes are a promising tool supporting voltammetric profiling of samples and this strategy, considering deep learning, can be developed to a large extent.

Electrochemical sensor based on Ni-exchanged natural zeolite/carbon black hybrid nanocomposite for determination of vitamin B6.

The utilization of environmentally friendly nanoporous natural zeolite exchanged with Ni2+ ions (NiZ) and conductive carbon black (CB) in the fabrication of a novel and selective voltammetric sensor of vitamin B6 (VB6) is presented. The used clinoptilolite-rich zeolite material and CB were characterized in terms of morphology and textural properties. The superior properties of Ni-zeolite/carbon black modified glassy carbon electrode (NiZCB-GCE), arising from the synergistic effect of combining the unique features of zeolite and conductive carbon black, were confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. In the determination of VB6 with the use of differential pulse voltammetry (DPV), the optimization of the pH value of supporting electrolyte and instrumental parameters, as well as the interference study were performed. Under optimized conditions, the oxidation peak current at the potential +0.72 V vs. Ag | AgCl | 3 M KCl reference electrode was linear to the VB6 concentration in the range 0.050 to 1.0 mg L-1 (0.30-5.9 µmol L-1) (R = 0.9993). The calculated limit of detection (LOD, S/N = 3), equal to 15 µg L-1 (0.09 µmol L-1), was much better compared to chemically modified electrodes with other carbon-based materials. The RSD for 0.5 mg L-1 was in the range 2.5-5.4% (n = 4). The developed NiZCB-GCE was successfully applied to the determination of VB6 in commercially available multivitamin dietary supplements, food, and water samples. The obtained recoveries ranged from 95 to 106%.

A voltammetric sensor based on mixed proton-electron conducting composite including metal-organic framework JUK-2 for determination of citalopram.

A voltammetric sensor has been developed based on glassy carbon electrode (GCE) modification with nanocomposite consisting of manganese-based metal-organic framework (JUK-2), multi-walled carbon nanotubes (MWCNTs), and gold nanoparticles (AuNPs) for detection of citalopram (CIT). The composition and morphology of JUK-2-MWCNTs-AuNPs/GCE were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy dispersion spectroscopy (EDS), and scanning electron microscopy (SEM). The electrochemical properties investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) indicated that the fabricated hybrid material exhibits the properties of mixed ion-electron conductor (MIEC). Using staircase voltammetry (SCV), under optimized conditions, the fabricated sensor shows a linear response in three CIT concentration ranges, 0.05-1.0, 1.0-10.0 and 15.0-115.0 µmol L-1, with a detection limit of 0.011 µmol L-1. The JUK-2-MWCNTs-AuNPs/GCE was successfully employed for the determination of CIT in pharmaceutical, environmental waters, and biological samples with satisfactory recoveries (98.6-104.8%).

3D-printed flow manifold based on potentiometric measurements with solid-state ion-selective electrodes and dedicated to multicomponent water analysis.

A 3D-printed flow manifold dedicated to potentiometric simultaneous determination of potassium, sodium, calcium and chloride in water is presented. The method is based on application of miniature solid-contact ion selective electrodes with a special design obtained with the use of 3D printing. The electrodes offer many attractive advantages including short response time and miniaturization feasibility. The use of the proposed novel electrodes enables performance of rapid potentiometric measurements in flow-injection technique and registration of many injection peaks in a short time. One of the advantages of using a special 3D-printed flow vessel for potentiometric measurements was miniaturization of electrodes and the possibility of integrating several (from three up to six) ion selective electrodes in one module enabling realization of multi-component analyses in the same time. Thanks to that the volume of each solution and measurement time were significantly reduced during multi-component analysis. In order to find out if the proposed manifold works properly, three multi-component synthetic samples and four certified reference materials were analyzed. The presented study shows that the proposed 3D-printed flow manifold with solid-state ion-selective electrodes could be an effective tool in a modern multi-component analysis meeting the requirements of green analytical chemistry.

Voltammetric determination of aluminum(III) as Al-Alizarin S complex in tea leaves and infusions.

This work presents, for the first time, DPV methodology of indirect aluminum (III) determination in tea leaves and infusions using the renewable silver amalgam electrode. A self-referencing strategy was proposed which relies on alternate voltammetric curves registration with and without conditioning of the electrode surface. The developed procedure utilizing formation of aluminum-Alizarin S complex shows linearity in the range of 2-50 µg L-1 of Al(III) concentration, with r > 0.997. In the case of the electrode conditioning LOD is 0.2 µgL-1 and repeatability expressed by CV is 1-2%. Introducing an additional operation i.e. electrode activation results in decrease of sensitivity from 0.0162 to 0.0043 µA/µgL-1. The method was verified using CRM (tea leaves). Due to the wide variety of tea origin, types and producers, four most popular sorts (black, green, red and white) were chosen, made by one manufacturer. It was demonstrated that the proposed methodology may be applied in Al(III) determination in tea leaves and infusions. Al(III) extraction effectiveness was also examined. It was verified, that lemon juice addition during brewing increases aluminum concentration in infusions. Using Principal Components Analysis it was demonstrated that automatic distinction of infusions brewed with and without lemon juice, based on unprocessed voltammetric signal, may be successfully realized.

Recent Applications of Silver Amalgam Electrodes for Analysis of Pharmaceuticals and Vitamins.

The features and applications of silver amalgam electrodes in electroanalysis of pharmaceuticals and vitamins are summarized in this review. The state-of-the-art in the preparation and construction of solid silver amalgam electrodes for prolonged and userfriendly use is presented. Although not as widely spread as other electrode materials, silver amalgam possesses a unique and viable combination of favorable electrochemical properties, which are close to ideal mercury electrodes, non-toxic character, high durability and mechanical stability, if properly prepared. Its capability of conducting the redox processes at highly negative potentials is essential for the analysis of large number of bioactive organic compounds. The review features also overview information for each application in drug or vitamin analysis divided to the sections according to the construction variants of silver amalgam electrodes.

Application of bismuth bulk annular band electrode for determination of ultratrace concentrations of thallium(I) using stripping voltammetry.

A study of a new type of mercury-free working electrode - the bismuth bulk annular band working electrode (BiABE) - applied for thallium(I) detection via differential pulse anodic stripping voltammetry (DP ASV), preceded by the complexation of interfering ions (Cd(2+), Pb(2+)) with EDTA in an acetate buffer (pH 4.5), is reported. The optimisation of experimental conditions included selection of the appropriate supporting electrolyte solution, potential and time of preconcentration, and DP mode parameters. The peak current was proportional to the concentration of Tl(I) in the range from 0.5 to 49nmolL(-1) (R=0.9992) and from 0.05 to 1.4nmolL(-1) (R=0.9987) for accumulation times of 60s and 300s, respectively. For 60s of accumulation time, the LOD was 0.005nmolL(-1) (1ngL(-1)) (at S/N=3), and the sensitivity of 18.5nA/nM was achieved. The relative standard deviation for 4.9nmolL(-1) of Tl(I) was 4.3% (n=5). Finally, the proposed method was successfully applied to determine Tl(I) in the certified reference materials-waters (SPS-SW1 and SPS-SW2) as well as the spiked tap and river water samples.

The renewable bismuth bulk annular band working electrode: fabrication and application in the adsorptive stripping voltammetric determination of nickel(II) and cobalt(II).

The paper presents the first report on fabrication and application of a user friendly and mercury free electrochemical sensor, with the renewable bismuth bulk annular band working electrode (RBiABE), in stripping voltammetry (SV). The sensor body is partly filled with the internal electrolyte solution, in which the RBiABE is cleaned and activated before each measurement. Time of the RBiABE contact with the sample solution is precisely controlled. The usefulness of this sensor was tested by Ni(II) and Co(II) traces determination by means of differential pulse adsorptive stripping voltammetry (DP AdSV), after complexation with dimethylglyoxime (DMG) in ammonia buffer (pH 8.2). The experimental variables (composition of the supporting electrolyte, pre-concentration potential and time, potential of the RBiABE activation, and DP parameters), as well as possible interferences, were investigated. The linear calibration graphs for Ni(II) and Co(II), determined individually and together, in the range from 1×10(-8) to 70×10(-8)molL(-1) and from 1×10(-9) to 70×10(-9)molL(-1) respectively, were obtained. The calculated limit of detection (LOD), for 30s of the accumulation time, was 3×10(-9)molL(-1) for Ni(II) in case of a single element's analysis, whereas the LOD was 5×10(-9)molL(-1) for Ni(II) and 3×10(-10)molL(-1) for Co(II), when both metal ions were measured together. The repeatability of the Ni(II) and Co(II) adsorptive stripping voltammetric signals obtained at the RBiABE were equal to 5.4% and 2.5%, respectively (n=5). Finally, the proposed method was validated by determining Ni(II) and Co(II) in the certified reference waters (SPS-SW1 and SPS-SW2) with satisfactory results.

Optimization of method for zinc analysis in several bee products on renewable mercury film silver based electrode.

Zinc is an interesting target for detection as it is one of the elements necessary for the proper functioning of the human body, its excess and deficiency can cause several symptoms. Several techniques including electrochemistry have been developed but require laboratory equipment, preparative steps and mercury or complex working electrodes. We here described the development of a robust, simple and commercially available electrochemical system. Differential pulse (DP) voltammetry was used for this purpose with the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) and 0.05 M KNO3 solution as a supporting electrolyte. The effect of various factors such as: preconcentration potential and time, pulse amplitude and width, step potential and supporting electrolyte composition are optimized. The limits of detection (LOD) and quantification (LOQ) were 1.62 ng/mL and 4.85 ng/mL, respectively. The repeatability of the method at a concentration level of the analyte as low as 3 ng/mL, expressed as RSD is 3.5% (n = 6). Recovery was determined using certified reference material: Virginia Tobacco Leaves (CTA-VTL-2). The recovery of zinc ranged from 96.6 to 106.5%. The proposed method was successfully applied for determination of zinc in bee products (honey, propolis and diet supplements) after digestion procedure.

Applicability of the silver amalgam electrode in voltammetric determination of zinc and copper in gastric juice and gastric mucosa of rats.

The aim of the work was to compare two analytical methods of trace analysis in respect to their applicability in heavy metals determination in biological samples. Atomic absorption spectrometry (AAS) may be considered as the method of choice in such analyses due to its accuracy, precision and low detection limit. On the other hand, voltammetric methods seem to be as useful, but rarely applied. Having in mind that there is no universal analytical method, we have compared two AAS and voltammetric methods as the tools for Zn and Cu determination in the samples collected from rat gastric juice and gastric mucosa. Construction of the renewable silver amalgam film electrode (Hg(Ag)FE) for stripping voltammetry was described. Detailed optimization of measurements procedure and sample preparation for differential pulse anodic stripping voltammetry (DP ASV) and AAS were also performed and presented. The obtained results of quantitative analysis of the chosen parameters by means of both methods are discussed.

Application of renewable silver amalgam annular band electrode to voltammetric determination of vitamins C, B1 and B2.

In this work, the design and results of applying silver liquid amalgam film-modified silver solid amalgam annular band electrode (AgLAF-AgSAE), refreshed before each measurement, to voltammetric determination of vitamins C (VC), B(1) (VB1) and B(2) (VB2) are presented. The method is based on adsorptive accumulation of analytes at the AgLAF-AgSAE in a phosphate buffer (VB1), phosphate buffer with Triton X-100 (VB2) and an alkaline borate buffer with Triton X-100 (VC). The analytical parameters and procedure of electrode activation were optimized. The calibration graphs obtained for vitamins C, B(1) and B(2) are linear, respectively, for concentration range 0.05-12, 0.01-0.1 and 0.05-3 mg L(-1). The detection limits were calculated and equaled 0.02, 0.003 and 0.009 mg L(-1), while repeatability of the peak current was 2%, 1% and 3%, respectively. These results are comparable with results obtained for polarographic determination of the same vitamins using mercury electrodes. Finally, the AgLAF-AgSAE was applied to the determination of vitamins in pharmaceutical samples and fruit juices with satisfactory results.

Chronic treatment with zinc and antidepressants induces enhancement of presynaptic/extracellular zinc concentration in the rat prefrontal cortex.

Zinc exhibits antidepressant-like activity in preclinical tests/models. Moreover, zinc homeostasis is implicated in the pathophysiology of affective disorders. The aim of the present study was to examine the effect of chronic zinc, citalopram and imipramine intraperitoneal administration on the presynaptic and extracellular zinc concentration in the rat prefrontal cortex and hippocampus. We used two methods: zinc-selenium histochemistry (which images the pool of presynaptic-vesicle zinc) and anodic stripping voltammetry (ASV) for zinc determination in microdialysate (which assays the extracellular zinc concentration). We report that chronic (14 ×) zinc (hydroaspartate, 10 and 65 mg/kg) and citalopram (20 mg/kg) administration increased the pool of presynaptic zinc (by 34, 50 and 37%, respectively) in the rat prefrontal cortex. The 21% increase induced by imipramine (20 mg/kg) was marginally significant. Likewise, zinc (hydroaspartate, 65 mg/kg), citalopram and imipramine increased the extracellular zinc (although with a different pattern: time point, area under the curve and/or basal level) in this brain region. Furthermore, zinc induced an increase in presynaptic (by 65%) and extracellular zinc (by 90%) in the hippocampus, while both citalopram and imipramine did not. These results indicate that all of the treatments increase presynaptic/extracellular zinc concentrations in the rat prefrontal cortex, which may then contribute to their antidepressant mechanisms. Alterations induced by zinc (but not antidepressants) administration in the hippocampus may be related to specific zinc mechanisms. All the data (previous and present) on the effect of antidepressant treatments on the presynaptic/extracellular zinc concentrations suggest the involvement of this biometal presynaptic/synaptic homeostasis in the antidepressant mechanism(s).

Development and validation of an anodic stripping voltammetric method for determination of Zn(2+) ions in brain microdialysate samples.

An easy, rapid, and sensitive anodic stripping voltammetric method with a controlled growth mercury drop electrode has been developed and validated for the determination of Zn(2+) ions in brain microdialysate samples obtained from rats. The considered level of the zinc concentration in the dialysate was 0.5-6 ppb. In the investigated method, the stripping step was carried out by using a differential pulse potential-time voltammetric excitation signal. The optimal experimental conditions as well as the instrumental and accumulation parameters and supporting electrolyte composition were investigated. The optimized method was validated for precision, linearity, and accuracy. Mean recovery 82-110% was achieved, the precision expressed by CV not greater than 7.6% and the linearity given by correlation coefficient not lower than 0.9988. The limit of detection was 0.1 ppb. No interferences were observed. Due to high linearity, precision, and sensitivity, the developed method may be successfully applied in the determination of zinc ions in microdialysate brain samples. The results obtained for the first time demonstrate detailed characteristics of the determination of zinc in the brain microdialysate fluid by the ASV method. It may be applied in a wide range of physiological and pharmacological studies which focus on very low zinc concentration/alteration in various compartments of the organisms.

Early lifetime zinc supplementation protects zinc-deficient diet-induced alterations.

Preclinical and clinical data indicate the involvement of zinc in the pathophysiology and therapy of depression. A relationship between zinc-deficiency and depression symptoms was recently proposed. The present study investigated alterations in spontaneous locomotor activity and zinc concentrations in the serum, hippocampus and frontal cortex; these alterations were induced by subjecting rats to a zinc-deficient diet, prior subjected after birth to zinc-supplemented diet. Body weight was significantly reduced in animals subjected to the four-week zinc-deficient diet compared to those subjected to the zinc-adequate diet. The two-week zinc-deficient diet induced a significant increase in locomotor activity in all measured time periods (5, 30 and 60 min by 44-62%). The four-week zinc-deficient diet did not affect locomotor activity, while the six-week zinc-deficient diet resulted in a 45% increase in the 5 min time period. Serum zinc concentrations were significantly reduced (by 29%) in animals subjected to the four-week zinc-deficient diet but not in those subjected to the two- or six-week zinc-deficient diets. The zinc-deficient diet did not influence the zinc concentration in the examined brain regions regardless of the length. These results indicate that post-birth supplementation with zinc may protect zinc-deficient diet-induced rapid alterations in zinc homeostasis.

End-point detection in potentiometric titration by continuous wavelet transform.

The aim of this work was construction of the new wavelet function and verification that a continuous wavelet transform with a specially defined dedicated mother wavelet is a useful tool for precise detection of end-point in a potentiometric titration. The proposed algorithm does not require any initial information about the nature or the type of analyte and/or the shape of the titration curve. The signal imperfection, as well as random noise or spikes has no influence on the operation of the procedure. The optimization of the new algorithm was done using simulated curves and next experimental data were considered. In the case of well-shaped and noise-free titration data, the proposed method gives the same accuracy and precision as commonly used algorithms. But, in the case of noisy or badly shaped curves, the presented approach works good (relative error mainly below 2% and coefficients of variability below 5%) while traditional procedures fail. Therefore, the proposed algorithm may be useful in interpretation of the experimental data and also in automation of the typical titration analysis, specially in the case when random noise interfere with analytical signal.

The cyclic renewable mercury film silver based electrode for determination of molybdenum(VI) traces using adsorptive stripping voltammetry.

The new cyclic renewable mercury film silver based electrode (Hg(Ag)FE), applied for the determination of molybdenum(VI) traces using differential pulse adsorptive cathodic stripping voltammetry (DP AdSV) is presented. The Hg(Ag)FE electrode is characterized by very good surface reproducibility (

The renovated silver ring electrode in determination of lead traces by differential pulse anodic stripping voltammetry.

The study of a new type of working electrode - the renovated silver ring electrode (RSRE) - for lead ions detection via differential pulse anodic stripping voltammetry (DP ASV) without removal of oxygen is reported. The only four constituents of the RSRE: a specially constructed silver ring electrode, a silver sheet used as silver counter/quasi-reference electrode and a silicon O-ring, are fastened together in a polypropylene body. The renovation of this electrode is carried out through mechanical removal of solid contaminants and electrochemical activation in the electrolyte which fills the RSRE body. Excellent repeatability and reproducibility - also in organic samples solutions - were reached in a period of a few weeks through the renovation of the electrode surface before each measurement. The reduction and stripping of lead on silver electrode under the DP ASV conditions are underpotential deposition/dissolution phenomena. The RSRE is used for the determination of Pb ions in concentrations ranging from 1 x 10(-9) to 1 x 10(-7)M. The repeatability of DP ASV runs in synthetic solutions covering the entire concentration range is better than 2%. Obtained calibration curves are represented by a correlation coefficient of at least 0.999. The detection limit (LOD) for the time of electrodeposition equal to 60s is 0.2 x 10(-9)M. LOD for Pb(2+) detection at the RSRE is similar to this reported for a rotating silver electrode in subtractive anodic stripping voltammetry (E. Kirowa-Eisner, et al., Anal. Chim. Acta, 385 (1999) 325). The analysis of Pb(2+) in synthetic solutions with and without surfactants, certified reference materials and natural water samples have been performed.