Bismuth Film along with dsDNA-Modified Electrode Surfaces as Promising (bio)Sensors in the Analysis of Heavy Metals in Soils.

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance.

Preparation of a glassy carbon electrode modified with saffron conjugated silver nanoparticles for the sensitive and selective electroanalytical determination of amoxicillin in urine samples.

Determination of antibiotics is crucial in order to assess their potential impacts on human health and the environment. This study aimed to develop a modified glassy carbon electrode with saffron conjugated silver nanoparticles for the determination of amoxicillin antibiotic in urine samples. The modified electrode was prepared by electrodeposition of silver nanoparticles on the electrode surface, followed by deposition of amoxicillin on the surface. The electrochemical behavior of the modified electrode was studied by cyclic voltammetry and square wave voltammetry. The results showed that the modified electrode exhibited enhanced electrocatalytic activity toward the oxidation of amoxicillin. The calibration curve was linear in the concentration range from 1.273 × 10-4 g L-1 to 2.217 × 10-3 g L-1, with a high linear correlation coefficient of 0.9998. The detection limit was determined to be 4.199 × 10-5 g L-1. The precision of the sensor was adequate, with relative standard deviations of 4.3% and 4.0% for AMX concentrations of 9.199 × 10-5 g L-1 and 1.194 × 10-4 g L-1, respectively. The modified electrode was then applied to the determination of amoxicillin in urine samples. The method showed linearity over the amoxicillin concentration range from 0.00 to 2.00 × 10-4 g L-1, with a detection limit of 9.739 × 10-6 g L-1, indicating the potential of the modified electrode for the determination of amoxicillin in biological samples. Overall, the modified glassy carbon electrode with silver nanoparticles showed very promising results for the sensitive and selective determination of amoxicillin in urine samples.

New Prospects in the Electroanalysis of Heavy Metal Ions (Cd, Pb, Zn, Cu): Development and Application of Novel Electrode Surfaces.

The detection of toxic heavy metal ions, especially cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu), is a global problem due to ongoing pollution incidents and continuous anthropogenic and industrial activities. Therefore, it is important to develop effective detection techniques to determine the levels of pollution from heavy metal ions in various media. Electrochemical techniques, more specifically voltammetry, due to its properties, is a promising method for the simultaneous detection of heavy metal ions. This review examines the current trends related to electrode formation and analysis techniques used. In addition, there is a reference to advanced detection methods based on the nanoparticles that have been developed so far, as well as formation with bismuth and the emerging technique of screen-printed electrodes. Finally, the advantages of using these methods are highlighted, while a discussion is presented on the benefits arising from nanotechnology, as it gives researchers new ideas for integrating these technologies into devices that can be used anywhere at any time. Reference is also made to the speciation of metals and how it affects their toxicity, as it is an important subject of research.

Different Aspects of the Voltammetric Detection of Vitamins: A Review.

Vitamins comprise a group of organic chemical compounds that contribute significantly to the normal functioning of living organisms. Although they are biosynthesized in living organisms, some are also obtained from the diet to meet the needs of organisms, which is why they are characterized as essential chemical compounds. The lack, or low concentrations, of vitamins in the human body causes the development of metabolic dysfunctions, and for this reason their daily intake with food or as supplements, as well as the control of their levels, are necessary. The determination of vitamins is mainly accomplished by using analytical methods, such as chromatographic, spectroscopic, and spectrometric methods, while studies are carried out to develop new and faster methodologies and techniques for their analysis such as electroanalytical methods, the most common of which are voltammetry methods. In this work, a study is reported that was carried out on the determination of vitamins using both electroanalytical techniques, the common significant of which is the voltammetry technique that has been developed in recent years. Specifically, the present review presents a detailed bibliographic survey including, but not limited to, both electrode surfaces that have been modified with nanomaterials and serve as (bio)sensors as well as electrochemical detectors applied in the determination of vitamins.

Development of an Electrochemical Sensor Using a Modified Carbon Paste Electrode with Silver Nanoparticles Capped with Saffron for Monitoring Mephedrone.

Mephedrone, also known as 4-methylmethcathinone, is growing into a prominent recreational drug for young people. When it came to detecting mephedrone, limited efforts were made using electrochemical sensors. As a result, this application depicts the fabrication of a new, sensitive, selective, and economical electrochemical sensor capable of detecting mephedrone by using silver nanoparticles capped with saffron produced through electropolymerization to modify carbon paste electrodes (CPEs). Silver nanoparticles (AgNPs) were capped with saffron (AgNPs@Sa) using a green method. AgNPs@Sa were studied using electron scanning microscopy (SEM) and UV-vis spectroscopy. The sensor was evaluated under the optimum condition to determine its analytical features. The results showed that this procedure had a wide linear range, low detection limit and sufficient reproducibility. Furthermore, the sensor posed sufficient stability. Moreover, it was applied in the determination of mephedrone in urine samples, showing the potential applicability of this electrochemical sensor in real sample analysis.

Selective Voltammetric Detection of Ascorbic Acid from Rosa Canina on a Modified Graphene Oxide Paste Electrode by a Manganese(II) Complex.

Voltammetric techniques have been considered as an important analytical tool applied to the determination of trace concentrations of many biological molecules including ascorbic acid. In this paper, ascorbic acid was detected by square wave voltammetry, using graphene oxide paste as a working electrode, modified by a film of a manganese(II) complex compound. Various factors, such as the effect of pH, affecting the response characteristics of the modified electrode were investigated. The relationship between the peak height and ascorbic acid concentration within the modified working electrode was investigated, using the calibration graph. The equation of the calibration graph was found to be: I = 0.0550γac + 0.155 with R2 = 0.9998, where I is the SWV current and γac is the mass concentration of ascorbic acid. The LOD and LOQ of the proposed method were determined to be 1.288 µg/L and 3.903 µg/L, respectively. Several compounds, such as riboflavin, biotin, and ions, such as Fe and Cu, were tested and it seemed that they did not interfere with the analytic signal. The proposed procedure was successfully applied in the determination of ascorbic acid in Rosa canina hips.

Electrochemical Behavior and Voltammetric Determination of a Manganese(II) Complex at a Carbon Paste Electrode.

Investigation of the electrochemical behavior using cyclic voltammetry and detection of [Mn(2+)(thiophenyl-2-carboxylic acid)2 (triethanolamine)] with adsorptive stripping differential pulse voltammetry. The electrochemical behavior of a manganese(II) complex [Mn(2+)(thiophenyl-2-carboxylic acid)2(triethanolamine)] (A) was investigated using cyclic and differential pulse voltammetry in an acetate buffer of pH 4.6 at a carbon paste electrode. Further, an oxidation-reduction mechanism was proposed. Meanwhile, an adsorptive stripping differential pulse voltammetric method was developed for the determination of manganese(II) complex.

Synthesis, characterization, DNA binding properties and antioxidant activity of a manganese(II) complex with NO6 chromophore.

The mononuclear complex [Mn(thiophenyl-2-carboxylate)(2)(H(3)tea)] (1), where H(3)tea=triethanolamine has been synthesized, characterized, while the DNA binding properties and the antioxidant activity were studied. The crystal structure of 1 is also reported. The interaction between 1 and calf thymus double stranded (ds) DNA was electrochemically at a calf thymus DNA (CT-DNA) modified carbon paste electrode (CPE) and spectrophotometrically investigated, respectively. Adsorptive transfer stripping voltammetry showed that the interaction mode between 1 and CT-DNA depends on manganese(II) complex concentration. UV studies between 1 and CT-DNA revealed that 1 can bind to CT-DNA by the intercalative binding mode and the binding constant has been calculated. A competitive study with acridine orange (AO) showed that 1 exhibits the ability to displace the DNA-bound AO, since 1 binds to the DNA in competition with AO. In vitro antioxidant activity of free ligands and 1 was evaluated using five different antioxidant assays: a) interaction with 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, b) the ΗΟ mediated oxidation of DMSO, c) scavenging of superoxide anion radicals, d) inhibition of lipid peroxidation and e) soybean lipoxygenase (LOX) inhibition. The results revealed the selectivity of the manganese complex to different free radicals as a consequence of its physicochemical feature. In particular, 1 presents significant inhibitory activity on LOX, with IC(50)=30 µM and selectivity to the inhibition of superoxide anion radicals and thus a promising candidate as a superoxide dismutase (SOD) biomimetic.

Electroanalytical study of SYBR Green I and ethidium bromide intercalation in methylated and unmethylated amplicons.

This work involves the electrochemical study of the interaction of SYBR Green I (SG) with native DNA using differential pulse voltammetry at a carbon paste electrode (CPE) and alternating current voltammetry at a hanging mercury drop electrode (HMDE). At the CPE the peak current intensity at 1.0 V decreased by increasing the concentration of SG. At the HMDE, a decrease in the current intensity of the DNA peak at -1.2 V was also observed by increasing the concentration of SG. These results electrochemically confirmed that SG intercalates within the DNA double helix and changes its conformation. Through the present work the differentiation of differently methylated analytes was achieved by application of alternative current and differential pulse voltammetric techniques. Amplicons (PCR products) corresponding to the GC-rich p53 exon 5 containing cytosine and its methylated analogue, synthesized by substituting 60% of cytosine by 5-methyl-cytosine, were amplified and investigated electrochemically in the presence of SG and ethidium bromide (EtBr) by differential pulse voltammetry. Considerable peak current differences were observed in the presence of SG and EtBr for unmethylated exon 5 vs. methylated. Therefore, both SG and EtBr could serve as electrochemical probes for identifying different DNA conformations.

Electroanalytical study of proflavine intercalation in 5-methyl or inosine-containing amplicons.

Amplicons corresponding to the GC-rich p53 exon 5 and its analogues, synthesized by substituting 60% of cytosine by 5-methyl-cytosine, or 60% of guanosine by inosine and GC-poor p53 exon 6 were synthesized and investigated electrochemically, in the presence and absence of proflavine, by differential pulse voltammetry (DPV). Incorporation of base analogues and the thermal stability of the resulting amplicons were tested in the presence of a fluorescent probe (Sybr-Green). Peak current at 1.0 V was lower for methylated than for unmethylated PCR amplicons and was similarly affected by proflavine intercalation. In contrast, considerable peak current differences were observed in the presence of proflavine for unmodified exon 5 v.s. exon 6 or inosine-containing amplicons. Thermal analysis verified the expected shifts in melting temperature (T (m)) due to the base analogue incorporation and GC-content variations. In conclusion, methylated and unmethylated PCR amplicons could be distinguished in model DNA systems using differential pulse voltammetry (DPV) and use of proflavine could serve as an electrochemical probe for identifying different DNA conformations.

Allele-specific genotyping by using guanine and gold electrochemical oxidation signals.

Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-specific genotyping is also one of the important research areas, where electrochemical approaches provide promising advances. Recently reported two methods based on electrochemical guanine and colloidal gold (Au) nanoparticle oxidation signals are reviewed and compared with the existing genotyping methods in this report.

Electrochemical detection of enzyme labeled DNA based on disposable pencil graphite electrode.

Electrochemical biosensor for the detection of DNA hybridization using the reduction signal of alpha-naphthol is described. A pencil graphite electrode was used as a working electrode. Capture probes were covalently attached on to the pencil graphite electrode surface (PGE) at the 5' end amino group by using N-(dimethylamino)propyl-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent on to PGE. After capture probe immobilization on to PGE surface; probe was hybridized with complementary biotinylated oligonucleotide. Alkaline phosphatase labeled with extravidin (Ex-AP) binds to biotinylated hybrid via biotin-avidin interaction. alpha-Naphthyl phosphate (alpha-NAP) was added and the reaction between alkaline phosphatase (AP) and alpha-NAP was occurred consequently as a substrate of AP, alpha-NAP reduction signal was obtained from this reaction, at -0.100 V by using differential pulse voltammetry (DPV). Other experimental parameters were studied such as; optimizations of hybridization time, and the concentrations of capture probe, biotinylated oligonucleotide and enzyme.