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Pencil graphite electrodes are a simple, disposable, and low-cost alternative to screen-printed graphite electrodes. In terms of stability and sensitivity, pencil electrodes often outperform conventional carbon ones. This paper discusses and emphasizes the superior properties of polymer pencil graphite electrodes (pPeGEs), which can be exploited in the electrochemical analysis of molecules, such as chlorides, whose signals are missing on common graphite electrodes. The chemical and structural behaviour of pencil leads after exposure to acids (HF, HNO3, HClO4) or organic solvents (CH3CN, CH3Cl) was monitored via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The electrochemical activity of pristine and treated pPeGEs was studied by the cyclic voltammetry (CV) responses of reversible redox probes [Fe(CN)6]3−/4− and [Ru(NH3)6]3+/2+. XPS proved the presence of siloxanes in the surface matrix of the pencil leads; this finding relates to the hydrophobic surface character of the electrodes. SEM then provided images of the pencil surfaces with microplates and flakes and revealed the removal of siloxanes upon chemical treatment. The CVs of non-dried and dried pPeGEs displayed surface changes in the polymer matrix, accompanied by water loss. Our study shows that the pPeGE retains the character of a stable graphite sensor when exposed to acids and organic solvents, except for HF and chloroform. The discovered effects explain the electrochemical processes occurring on pPeGEs and can contribute to their application in electrochemical sensing and energy storage.

Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications.

In electrochemical sensing, a number of voltammetric or amperometric curves are obtained which are subsequently processed, typically by evaluating peak currents and peak potentials or wave heights and half-wave potentials, frequently after background correction. Transformations of voltammetric data can help to extract specific information, e.g., the number of transferred electrons, and can reveal aspects of the studied electrochemical system, e.g., the contribution of adsorption phenomena. In this communication, we introduce a LabView-based software package, ‘eL-Chem Viewer’, which is for the analysis of voltammetric and amperometric data, and enables their post-acquisition processing using semiderivative, semiintegral, derivative, integral and elimination procedures. The software supports the single-click transfer of peak/wave current and potential data to spreadsheet software, a feature that greatly improves productivity when constructing calibration curves, trumpet plots and performing similar tasks. eL-Chem Viewer is freeware and can be downloaded from www.lchem.cz/elchemviewer.htm.

Since its first official detection in the Guangdong province of China in 1996, the highly pathogenic avian influenza virus of H5N1 subtype (HPAI H5N1) has reportedly been the cause of outbreaks in birds in more than 60 countries, 24 of which were European. The main issue is still to develop effective antiviral drugs. In this case, single point mutation in the neuraminidase gene, which causes resistance to antiviral drug and is, therefore, subjected to many studies including ours, was observed. In this study, we developed magnetic electrochemical bar code array for detection of single point mutations (mismatches in up to four nucleotides) in H5N1 neuraminidase gene. Paramagnetic particles Dynabeads® with covalently bound oligo (dT)25 were used as a tool for isolation of complementary H5N1 chains (H5N1 Zhejin, China and Aichi). For detection of H5N1 chains, oligonucleotide chains of lengths of 12 (+5 adenine) or 28 (+5 adenine) bp labeled with quantum dots (CdS, ZnS and/or PbS) were used. Individual probes hybridized to target molecules specifically with efficiency higher than 60%. The obtained signals identified mutations present in the sequence. Suggested experimental procedure allows obtaining further information from the redox signals of nucleic acids. Moreover, the used biosensor exhibits sequence specificity and low limits of detection of subnanogram quantities of target nucleic acids.

Cadmium, as a hazardous pollutant commonly present in the living environment, represents an important risk to human health due to its undesirable effects (oxidative stress, changes in activities of many enzymes, interactions with biomolecules including DNA and RNA) and consequent potential risk, making its detection very important. New and unique technological and biotechnological approaches for solving this problems are intensely sought. In this study, we used the commonly occurring potential pathogenic microorganism Staphylococcus aureus for the determination of markers which could be used for sensing of cadmium(II) ions. We were focused on monitoring the effects of different cadmium(II) ion concentrations (0, 1.25, 2.5, 5, 10, 15, 25 and 50 µg mL−1) on the growth and energetic metabolism of Staphylococcus aureus. Highly significant changes have been detected in the metabolism of thiol compounds—specifically the protein metallothionein (0.79–26.82 mmol/mg of protein), the enzyme glutathione S-transferase (190–5,827 µmol/min/mg of protein), and sulfhydryl groups (9.6–274.3 µmol cysteine/mg of protein). The ratio of reduced and oxidized glutathione indicated marked oxidative stress. In addition, dramatic changes in urease activity, which is connected with resistance of bacteria, were determined. Further, the effects of cadmium(II) ions on the metabolic pathways of arginine, β-glucosidase, phosphatase, N-acetyl β-D-glucosamine, sucrose, trehalose, mannitol, maltose, lactose, fructose and total proteins were demonstrated. A metabolomic profile of Staphylococcus aureus under cadmium(II) ion treatment conditions was completed seeking data about the possibility of cadmium(II) ion accumulation in cells. The results demonstrate potential in the application of microorganisms as modern biosensor systems based on biological components.

The aim of this study was to describe behaviour, kinetics, time courses and limitations of the six different fully automated spectrometric methods - DPPH, TEAC, FRAP, DMPD, Free Radicals and Blue CrO5. Absorption curves were measured and absorbance maxima were found. All methods were calibrated using the standard compounds Trolox® and/or gallic acid. Calibration curves were determined (relative standard deviation was within the range from 1.5 to 2.5 %). The obtained characteristics were compared and discussed. Moreover, the data obtained were applied to optimize and to automate all mentioned protocols. Automatic analyzer allowed us to analyse simultaneously larger set of samples, to decrease the measurement time, to eliminate the errors and to provide data of higher quality in comparison to manual analysis. The total time of analysis for one sample was decreased to 10 min for all six methods. In contrary, the total time of manual spectrometric determination was approximately 120 min. The obtained data provided good correlations between studied methods (R = 0.97 – 0.99).

Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic.

We used carbon paste electrodes and a standard potentiostat to detect silver ions. The detection limit (3 Signal/Noise ratio) was estimated as 0.5 μM. A standard electrochemical instrument microanalysis of silver(I) ions was suggested. As a working electrode a carbon tip (1 mL) or carbon pencil was used. Limits of detection estimated by dilution of a standard were 1 (carbon tip) or 10 nM (carbon pencil). Further we employed flow injection analysis coupled with carbon tip to detect silver(I) ions released in various beverages and mineral waters. During first, second and third week the amount of silver(I) ions releasing into water samples was under the detection limit of the technique used for their quantification. At the end of a thirteen weeks long experiment the content of silver(I) ions was several times higher compared to the beginning of release detected in the third week and was on the order of tens of nanomoles. In subsequent experiments the influence of silver(I) ions (0, 5 and 10 μM) on a plant model system (tobacco BY-2 cells) during a fourday exposition was investigated. Silver(I) ions were highly toxic to the cells, which was revealed by a double staining viability assay. Moreover we investigated the effect of silver(I) ions (0, 0.3, 0.6, 1.2 and 2.5 μM) on guppies (Poecilia reticulata). Content of Ag(I) increased with increasing time of the treatment and applied concentrations in fish tissues. It can be concluded that a carbon tip or carbon pencil coupled with a miniaturized potentiostat can be used for detection of silver(I) ions in environmental samples and thus represents a small, portable, low cost and easy-to-use instrument for such purposes.

Chloride ion sensing is important in many fields such as clinical diagnosis, environmental monitoring and industrial applications. We have measured chloride ions at a carbon paste electrode (CPE) and at a CPE modified with solid AgNO3, a solution of AgNO3 and/or solid silver particles. Detection limits (3 S/N) for chloride ions were 100 μM, 100 μM and 10 μM for solid AgNO3, solution of AgNO3 and/or solid silver particles, respectively. The CPE modified with silver particles is the most sensitive to the presence chloride ions. After that we approached to the miniaturization of the whole electrochemical instrument. Measurements were carried out on miniaturized instrument consisting of a potentiostat with dimensions 35 × 166 × 125 mm, screen printed electrodes, a peristaltic pump and a PC with control software. Under the most suitable experimental conditions (Britton-Robinson buffer, pH 1.8 and working electrode potential 550 mV) we estimated the limit of detection (3 S/N) as 500 nM.

Among wide spectrum of biomolecules induced by various stress factors low molecular mass protein called metallothionein (MT) is suitable for assessment of the heavy metal environmental pollution. The aim of this work was to determine the metallothionein and total thiols content in larvae of freshwater midges (Chironomus riparius) sampled from laboratory exposure to cadmium(II) ions and from field studies using differential pulse voltammetry Brdicka reaction. Unique electrochemical instrument, stationary electrochemical analyser Autolab coupled with autosampler, was utilized for the analysis of the samples. The detection limit for MT was evaluated as 5 nM. The larvae exposed to two doses (50 ng/g or 50 μg/g) of cadmium(II) ions for fifteen days under laboratory controlled conditions were at the end of the exposure killed, homogenized and analysed. MT content in control samples was 1.2 μM, in larvae exposed to 50 ng Cd/g it was 2.0 μM and in larvae exposed to 50 μg Cd/g 2.9 μM. Moreover at field study chironomid larvae as well as sediment samples have been collected from eight field sites with different levels of pollution by heavy. The metals content (chromium, nickel, copper, zinc, arsenic, molybdenum, cadmium, tin and lead) in the sediment and or MT content in the chironomid larvae were determined by inductively coupled plasma mass spectrometry or Brdicka reaction, respectively.

In the paper we utilized the adsorptive transfer stripping differential pulse voltammetry Brdicka reaction for the determination of metallothioneins (MT) in melanoma cells, animal melanoma tissues (MeLiM miniature pig) and blood serum of patients with malignant melanoma. Primarily we attempted to investigate the influence of dilution of real sample on MT electrochemical response. Dilution of samples of 1 000 times was chosen the most suitable for determination of MT level in biological samples. Then we quantified the MT level in the melanoma cells, the animal melanoma tissues and the blood serum samples. The MT content in the cells varied within the range from 4.2 to 11.2 μM. At animal melanoma tissues (melanomas localized on abdomen, back limb and dorsum) the highest content of MT was determined in the tumour sampled on the back of the animal and was nearly 500 μg of MTs per gram of a tissue. We also quantified content of MT in metastases, which was found in liver, spleen and lymph nodes. Moreover the average MT level in the blood serum samples from patients with melanoma was 3.0 ± 0.8 μM. MT levels determined at melanoma samples were significantly (p < 0.05) higher compared to control ones at cells, tissues and blood serum.

An Electrochemical Detection of Metallothioneins at the Zeptomole Level in Nanolitre VolumesWe report on improvement of the adsorptive transfer stripping technique (AdTS) coupled with the differential pulse voltammetry Brdicka reaction to determine a thiol-protein. The current technique has been unable to generate reproducible results when analyzing very low sample volumes (nanolitres). This obstacle can be overcome technically by modifying the current transfer technique including cooling step of the adsorbed analyte. We tested the technique on determination of a promising tumour disease marker protein called metallothionein (MT). The detection limit (3 S/N) of MT was evaluated as 500 zeptomoles per 500 nL (1 pM) and the quantification limit (10 S/N) as 1,500 zeptomoles per 500 nL (3 pM). Further, the improved AdTS technique was utilized to analyze blood serum samples from patients with breast cancer. Based on the results obtained it can be concluded that the improved technique can be used to detect a thiolprotein in very low sample volumes and can also prevent interferences during the washing and transferring step.

Using a paraffin impregnated graphite electrode (PIGE) and mercury-modifiedpyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNApurine base solutions have been studied by cyclic (CV) and linear sweep voltammetry(LSV) in connection with elimination voltammetry with linear scan (EVLS). In chlorideand bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with twocathodic and two anodic potentially separated signals. According to the eliminationfunction E4, the first cathodic peak corresponds to the reduction Cu(II) e- → Cu(I) withthe possibility of fast disproportionation 2Cu(I) → Cu(II) Cu(0). The E4 of the secondcathodic peak signalized an electrode process controlled by a surface reaction. Theelectrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by onecathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodicstripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where thereduction of copper ions took place and Cu(I)-purine complexes were formed. By usingASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complexdetection was enhanced relative to either ASV or CSV alone, resulting in higher peakcurrents of more than one order of magnitude. The statistical treatment of CE data wasused to determine the reproducibility of measurements. Our results show that EVLS inconnection with the stripping procedure is useful for both qualitative and quantitativemicroanalysis of purine derivatives and can also reveal details of studied electrodeprocesses.

About biological affecting of flavonoids on animal organisms is known less,thus we selected flavonoids, flavanones and flavones, and their glycosides, which wereexamined as potential inducers of cytochrome(s) P450 when administrated by gavages intoexperimental male rats. The study was focused on induction of CYP1A1, the majorcytochrome P450 involved in carcinogen activation. The data obtained demonstrate thenecessity of taking into account not only ability of flavonoids to bind to Ah receptor(induction factor) but also to concentrate on their distribution and metabolism (includingcolon microflora) in the body. After that we examined certain flavonoids as potential inducers of cytochrome P450, we wanted to suggest and optimize suitable electrochemical technique for determination of selected flavonoids (quercetin, quercitrin, rutin, chrysin and diosmin) in body liquids. For these purposes, we selected square wave voltannetry using carbon paste electrode. Primarily we aimed on investigation of their basic electrochemical behaviour. After that we have optimized frequency, step potential and supporting electrolyte. Based on the results obtained, we selected the most suitable conditions for determination of the flavonoids as follows: frequency 180 Hz, step potential 1.95 mV/s and phosphate buffer of pH 7 as supporting electrolyte. Detection limits (3 S/N) of the flavonoids were from units to tens of nM except diosmin, where the limit were higher than μM. In addition, we attempted to suggest a sensor for analysis of flavonoids in urine. It clearly follows from the results obtained that flavonoids can be analysed in the presence of animal urine, because urine did not influence much the signals of flavonoids (recoveries of the signals were about 90 %).

Metallothioneins play a key role in maintaining homeostasis of essential metalsand in protecting of cells against metal toxicity as well as oxidative damaging. Exceptinghumans, blood levels of metallothionein have not yet been reported from any animalspecies. Blood plasma samples of 9 animal species were analysed by the adsorptive transferstripping technique to obtain species specific voltammograms. Quite distinct records wereobtained from the Takin (Budorcas taxicolor), while other interesting records were observedin samples from the European Bison (Bison bonasus bonasus) and the Red-eared Slider(Trachemys scripta elegans). To quantify metallothionein the catalytic peak Cat2 was used,well developed in the Domestic Fowl (Gallus gallus f. domestica) and showing a very lowsignal in the Red Deer (Cervus elaphus). The highest levels of metallothionein reachingover 20 μM were found in the Domestic Fowl. High levels of MT were also found in theBearded Dragon (Pogona vitticeps) and the Grey Wolf (Canis lupus lupus). The lowestvalues of about 1-3 μM were determined in the Red-eared Slider, Takin and Red Deer. Employing a simple electrochemical detection it was possible to examine variation in blood metallothionein in different species of vertebrates.

Urease is the enzyme catalyzing the hydrolysis of urea into carbon dioxide andammonia. This enzyme is substrate-specific, which means that the enzyme catalyzes thehydrolysis of urea only. This feature is a basic diagnostic criterion used in thedetermination of many bacteria species. Most of the methods utilized for detection ofurease are based on analysis of its enzyme activity – the hydrolysis of urea. The aim of thiswork was to detect urease indirectly by spectrometric method and directly by voltammetricmethods. As spectrometric method we used is called indophenol assay. The sensitivity ofdetection itself is not sufficient to analyse the samples without pre-concentration steps.Therefore we utilized adsorptive transfer stripping technique coupled with differential pulse voltammetry to detect urease. The influence of accumulation time, pH of supporting electrolyte and concentration of urease on the enzyme peak height was investigated. Under the optimized experimental conditions (0.2 M acetate buffer pH 4.6 and accumulation time of 120 s) the detection limit of urease evaluated as 3 S/N was 200 ng/ml. The activity of urease enzyme depends on the presence of nickel. Thus the influence of nickel(II) ions on electrochemical response of the enzyme was studied. Based on the results obtained the interaction of nickel(II) ions and urease can be determined using electrochemical methods. Therefore we prepared Ni nanoelectrodes to measure urease. The Ni nanoelectrodes was analysed after the template dissolution by scanning electron microscopy. The results shown vertically aligned Ni nanopillars almost covered the electrode surface, whereas the defect places are minor and insignificant in comparison with total electrode surface. We were able to not only detect urease itself but also to distinguish its native and denatured form.

Despite very intensive research in the synthesising of new cytostatics, cisplatin isstill one of the most commonly used anticancer drugs. Therefore, an investigation ofinteractions of cisplatin with different biologically important amino acids, peptides andproteins is very topical. In the present paper, we utilized flow injection analysis coupledwith electrochemical detection to study and characterize the behaviour of various forms ofglutathione (reduced glutathione – GSH, oxidized glutathione – GSSG and S-nitrosoglutathione – GSNO). The optimized conditions were as follows: mobile phase consistedof acetate buffer (pH 3) with a flow rate of 1 mL min-1. Based on results obtained we chose850 mV as the optimal potential for detection of GSH and 1,100 mV as the optimalpotential for detection of GSSG and GSNO. The detection limits of GSH, GSSG andGSNO were 100 pg mL-1, 50 ng mL-1 and 300 pg mL-1, respectively. Further, the optimized technique was used for investigation of interactions between cisplatin and GSH. We were able to observe the interaction between GSH and cisplatin via decrease in the signal corresponding to glutathione. Moreover, we evaluated the formation of the complex by spectrometry. The spectrometric results obtained were in good agreement with electrochemical ones.

Due to unique physico-chemical properties of –SH moiety thiols comprise widegroup of biologically important compounds. A review devoted to biological functions ofglutathione and phytochelatins with literature survey of methods used to analysis of thesecompounds and their interactions with cadmium(II) ions and Murashige-Skoog medium ispresented. For these purposes electrochemical techniques are used. Moreover, we revealedthe effect of three different cadmium concentrations (0, 10 and 100 μM) on cadmiumuptake and thiols content in maize plants during 192 hours long experiments usingdifferential pulse anodic stripping voltammetry to detect cadmium(II) ions and highperformance liquid chromatography with electrochemical detection to determineglutathione. Cadmium concentration determined in tissues of the plants cultivated innutrient solution containing 10 μM Cd was very low up to 96 hours long exposition andthen the concentration of Cd markedly increased. On the contrary, the addition of 100 μMCd caused an immediate sharp increase in all maize plant parts to 96 hours Cd expositionbut subsequently the Cd concentration increased more slowly. A high performance liquidchromatography with electrochemical detection was used for glutathione determination intreated maize plants after 96 and 192 hours of treatment. The highest total content of glutathione per one plant was 6 μg (96 h, 10 μM Cd) in comparison with non-treated plant (control) where glutathione content was 1.5 μg. It can be concluded that electrochemical techniques have proved to be useful to analyse plant thiols.

The main aim of this work was to use multi-instrumental analytical apparatus toinvestigate the effects of treatment with cadmium(II) and/or lead(II) ions (50, 250 and 500μM) for twelve days on early somatic spruce embryos (ESEs). Primarily we used imageanalysis for estimation of growth and a fluorimetric sensor for enzymatic detection ofviability of the treated ESEs. It follows from the obtained results that Cd caused highertoxicity to ESEs than Pb. Besides this fundamental finding, we observed that ESEs grewand developed better in the presence of 500 μM of the metal ions than in the presence of250 μM. Based on the results obtained using nuclear magnetic resonance this phenomenonwas related to an increase of the area of ESE clusters by intensive uptake of water from thecultivation medium, due to dilution of the heavy metal concentration inside the cluster. Inaddition we studied the glutathione content in treated ESEs by the adsorptive transferstripping technique coupled with the differential pulse voltammetry Brdicka reaction. GSHcontents increased up to 148 ng/mg (clone 2/32) and 158 ng/mg (clone PE 14) after twelve day long treatment with Cd-EDTA ions. The GSH content was about 150 and 160 % higher in comparison with the ESEs treated with Pb-EDTA ions, respectively. The difference between GSH contents determined in ESEs treated with Pb-EDTA and Cd-EDTA ions correlates with the higher toxicity of cadmium(II) ions.

Miniaturization and integration of chemical devices into modules that aredimensionally comparable with electronic chips (Lab on Chip) is nowadays developingworldwide. The aim of our work was to suggest and optimize the best conditions forfabrication of TFT sensor due to its sensitivity and low experimental deviations. Newelectrochemical analytical device was developed to ensure certain known mass transport toelectrodes, which is the most limiting process that influencing the response quality of thesensor. The device consists from rotating conic vessel for measured sample and stick-inthick-film sensor. The sensors responses were tested under trace analysis of cadmium.Measurements were done also with the others electrochemical arrangements to comparewith the new one. The sensor output current response dependence on the liquid velocity andgeometrical arrangement within using standard electrochemical couple of potassiumferrocyanide-ferricyanide is presented. We found out that the new device with controlledflow of electrolyte to sensor worked properly and gave satisfactory results.

The paper describes successful coupling of adsorptive transfer stripping (AdTS) andelimination voltammetry with linear scan (EVLS) for the resolution of reduction signals of cytosine (C)and adenine (A) residues in hetero-oligodeoxynucleotides (ODNs). Short ODNs (9-mers and 20-mers)were adsorbed from a small volume on a hanging mercury drop electrode (HMDE). After washing ofthe ODN-modified electrode by water and its transferring to an electrochemical cell, voltammetric curves were measured. The AdTS EVLS was able to determine of C/A ratio of ODNs through theelimination function conserving the diffusion current component and eliminating kinetic and chargingcurrent components. This function, which provides the elimination signal in a peak-counterpeak form,increased the current sensitivity for A and C resolution, and for the recognition of bases sequences inODN chains. Optimal conditions of elimination experiments such as pH, time of adsorption, and scanrate were found. The combination of EVLS with AdTS procedure can be considered as a newdetection method in a DNA sensor.

Electrochemical biosensors have superior properties over other existingmeasurement systems because they can provide rapid, simple and low-cost on-fielddetermination of many biological active species and a number of dangerous pollutants. Inour work, we suggested a new heavy metal biosensor based on interaction of heavy metalions (Cd2+ and Zn2+ ) with phytochelatin, which was adsorbed on the surface of the hangingmercury drop electrode, using adsorptive transfer stripping differential pulse voltammetry.In addition, we applied the suggested technique for the determination of heavy metals in abiological sample – human urine and platinum in a pharmaceutical drug. The detectionlimits (3 S/N) of Cd(II), Zn(II) and cis-platin were about 1.0, 13.3 and 1.9 pmole in 5 μl,respectively. On the basis of the obtained results, we propose that the suggested techniqueoffers simple, rapid, and low-cost detection of heavy metals in environmental, biologicaland medical samples.

BACKGROUND: Proteomics and metalloproteomics are rapidly developing interdisciplinary fields providing enormous amounts of data to be classified, evaluated and interpreted. Approaches offered by bioinformatics and also by biostatistical data analysis and treatment are therefore of extreme interest. Numerous methods are now available as commercial or open source tools for data processing and modelling ready to support the analysis of various datasets. The analysis of scientific data remains a big challenge, because each new task sets its specific requirements and constraints that call for the design of a targeted data pre-processing approach. METHODOLOGY/PRINCIPAL FINDINGS: This study proposes a mathematical approach for evaluating and classifying datasets obtained by electrochemical analysis of metallothionein in rat 9 tissues (brain, heart, kidney, eye, spleen, gonad, blood, liver and femoral muscle). Tissue extracts were heated and then analysed using the differential pulse voltammetry Brdicka reaction. The voltammograms were subsequently processed. Classification models were designed making separate use of two groups of attributes, namely attributes describing local extremes, and derived attributes resulting from the level=5 wavelet transform. CONCLUSIONS/SIGNIFICANCE: On the basis of our results, we were able to construct a decision tree that makes it possible to distinguish among electrochemical analysis data resulting from measurements of all the considered tissues. In other words, we found a way to classify an unknown rat tissue based on electrochemical analysis of the metallothionein in this tissue.

BackgroundThiol-rich peptides and proteins possess a large number of biological activities and may serve as markers for numerous health problems including cancer. Metallothionein (MT), a small molecular mass protein rich in cysteine, may be considered as one of the promising tumour markers. The aim of this paper was to employ chronopotentiometric stripping analysis (CPSA) for highly sensitive detection of MT.Methodology/principal findingsIn this study, we used adsorptive transfer stripping technique coupled with CPSA for detection of cysteine, glutathione oxidized and reduced, phytochelatin, bovine serum albumin, and metallothionein. Under the optimal conditions, we were able to estimate detection limits down to tens of fg per ml. Further, this method was applied to detect metallothioneins in blood serum obtained from patients with breast cancer and in neuroblastoma cells resistant and sensitive to cisplatin in order to show the possible role of metallothioneins in carcinogenesis. It was found that MT level in blood serum was almost twice higher as compared to the level determined in healthy individuals.Conclusions/significanceThis paper brings unique results on the application of ultra-sensitive electroanalytical method for metallothionein detection. The detection limit and other analytical parameters are the best among the parameters of other techniques. In spite of the fact that the paper is mainly focused on metallothionein, it is worth mentioning that successful detection of other biologically important molecules is possible by this method. Coupling of this method with simple isolation methods such as antibody-modified paramagnetic particles may be implemented to lab-on-chip instrument.

Diabetes mellitus represents one of the most widespread diseases in civilization nowadays. Since the costs for treating and diagnosing of diabetes represent several billions of dollars per year, a cheap, fast, and simple sensor for diabetes diagnosis is needed. Electrochemical insulin sensors can be considered as a novel approach for diabetes diagnosis. In this study, carbon electrode with electrodeposited NiO nanoparticles was selected as a suitable electrode material for insulin determination. The morphology and surface composition were studied by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). For a better understanding of insulin determination on NiO-modified electrodes, the mechanism of electrochemical reaction and the kinetic parameters were studied. They were calculated from both voltammetric and amperometric measurements. The modified carbon electrode displayed a wide linear range from 600 nM to 10 µM, a low limit of detection of 19.6 nM, and a high sensitivity of 7.06 µA/µM. The electrodes were stable for 30 cycles and were able to detect insulin even in bovine blood serum. Additionally, the temperature stability of this electrode and its storage conditions were studied with appropriate outcomes. The above results show the high promise of this electrode for detecting insulin in clinical samples.