Novel CNT Supported Molybdenum Catalyst for Detection of L-Cysteine in Its Natural Environment

In this study, novel carbon nanotube-supported Mo (Mo/CNT) catalysts were prepared with the sodium borohydride reduction method for the detection of L-cysteine (L-Cys, L-C). Mo/CNT catalysts were characterized with scanning electron microscopy with elemental dispersion X-ray (EDX-SEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectrometry (UV-vis), temperature-programmed reduction (TPR), temperature programmed oxidation (TPO), and temperature-programmed desorption (TPD) techniques. The results of these advanced surface characterization techniques revealed that the catalysts were prepared successfully. Electrochemical measurements were employed to construct a voltammetric L-C sensor based on Mo/CNT catalyst by voltammetric techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Further measurements were carried out with electrochemical impedance spectroscopy (EIS). Mo/CNT/GCE exhibited excellent performance for L-C detection with a linear response in the range of 0–150 µM, with a current sensitivity of 200 mA/μM cm2 (0.0142 μA/μM), the lowest detection limit of 0.25 μM, and signal-to-noise ratio (S/N = 3). Interference studies showed that the Mo/CNT/GCE electrode was not affected by D-glucose, uric acid, L-tyrosine, and L-trytophane, commonly interfering organic structures. Natural sample analysis was also accomplished with acetyl L-C. Mo/CNT catalyst is a promising material as a sensor for L-C detection.

Quantification of Platinum in Edible Mushrooms Using Voltammetric Techniques

Edible mushrooms are a food source with interesting nutritional values. The chief objective of this research was to develop a consistent method for the quantitative ultra-trace analysis of Pt in mushrooms, which is complex because it cannot be readily quantified by common analytical procedures. This research is one of the first analytical methods to establish Pt amount in these vegetables. In this research, 28 different edible mushroom samples from Italy were investigated. Determination of Pt in mushrooms was completed using Differential Pulse Voltammetry (DPV). In this study, we applied the standard addition method because there are no certified reference mushrooms containing platinum group elements on the market. The platinum quantification limit was 0.03 µg kg−1 d.w. In the analyzed samples, platinum amount was in the range of 0.03–73 µg kg−1. Our mushroom samples had a Pt content lower than the concentrations recommended by international establishments for other foodstuffs. In the future, the optimized method could be used for the analysis of plant and animal matrices intended for food supply.

Differential Pulse Voltammetry as an Alternative Method for Tracking Hydrochlorothiazide Electrolytic Degradation

This study aims to compare differential pulse voltammetry as a tracking method with chromatography and photometry. The three methods were used to track the degradation of the model compound hydrochlorothiazide (HCT) where 250ml of 0.50mM HCT solution (pH of 3.50 and ionic strength of 0.010M) was electrolyzed with 50.0mAmp constant current. The degradation process demonstrated great fit (R2 >0.99) with pseudo-first-order kinetics when the three tracking methods were utilized. However, different rate constants were reported for these methods: 0.032min-1, 0.016 min-1, and 0.0052min-1 for the chromatographic, photometric, and voltammetric techniques, respectively. The observed variation was attributed to the nature of the utilized probing methods. The differential pulse voltammetry is promising as an electrolytic decomposition tracking method; however, the working probe to target pollutants needs to be improved.

What Can Electrochemical Methods Offer in Determining DNA–Drug Interactions?

The interactions of compounds with DNA have been studied since the recognition of the role of nucleic acid in organisms. The design of molecules which specifically interact with DNA sequences allows for the control of the gene expression. Determining the type and strength of such interaction is an indispensable element of pharmaceutical studies. Cognition of the therapeutic action mechanisms is particularly important for designing new drugs. Owing to their sensitivity, simplicity, and low costs, electrochemical methods are increasingly used for this type of research. Compared to other techniques, they require a small number of samples and are characterized by a high reliability. These methods can provide information about the type of interaction and the binding strength, as well as the damage caused by biologically active molecules targeting the cellular DNA. This review paper summarizes the various electrochemical approaches used for the study of the interactions between pharmaceuticals and DNA. The main focus is on the papers from the last decade, with particular attention on the voltammetric techniques. The most preferred experimental approaches, the electrode materials and the new methods of modification are presented. The data on the detection ranges, the binding modes and the binding constant values of pharmaceuticals are summarized. Both the importance of the presented research and the importance of future prospects are discussed.

Triclosan: Electrochemistry, Spontaneous Degradation and Effects on Double-Stranded DNA

Triclosan (TCS) is an antiseptic agent widely used mainly in personal care products and an important contaminant, which degrades in the environment causing toxicity on health, including negative effects on DNA. In this context, an electrochemical investigation of TCS in aqueous solution was studied by voltammetric techniques. The TCS underwent irreversible oxidation in a pH-dependent process, leading to the formation of two reversibly oxidized and pH-dependent oxidation products. An oxidation mechanism for TCS and its oxidation products in neutral aqueous medium was proposed. Besides that, the TCS spontaneously degraded into supporting eletrolytes with 3.4 ≤ pH ≤ 12.04 over the incubation time and the degraded TCS in solution was detected by electrochemical and spectrophotometric techniques. A higher degradation of TCS was observed in alkaline medium. In addition, the interaction in situ of this anti-microbial with DNA was investigated using dsDNA incubated solutions and dsDNA electrochemical bisosensor, by voltammetry. TCS and degraded TCS interacted with dsDNA causing the condensation of the double helix structure, release of guanine (by TCS and dedraded TCS) and adenine (by degraded TCS) bases from dsDNA and a possible intercalation of degraded TCS in the polynucleotide chain. No dsDNA oxidative damage was detected.

Differential Pulse Anodic Voltammetric Determination of Chlorzoxazone in Pharmaceutical Formulation using Carbon Paste Electrode

The electrochemical behavior of chlorzoxazone at the carbon paste electrode was investigated in 0.04 mol/L Britton-Robinson buffer pH 6.50 using cyclic and differential pulse voltammetric techniques. Cyclic voltammetric studies indicated that the oxidation of the drug was irreversible and controlled mainly by diffusion. Experimental and instrumental parameters were optimized (50 mV/s scan rate, 50 mV pulse amplitude, and 0.04 mol/L Britton-Robinson (BR) buffer pH 6.50 as a supporting electrolyte) and a sensitive differential pulse anodic voltammetric method has been developed for the determination of the drug over the concentration range 0.17–1.68 μg/mL chlorzoxazone, with detection and quantitation limits of 0.05 and 0.16 μg/mL, respectively. The proposed voltammetric method was successfully applied to the determinationof the drug in its pharmaceutical formulation (Myoflex tablets), and in spiked human urine samples.

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

Crown ethers are common building blocks in supramolecular chemistry and are frequently applied as cation sensors or as subunits in synthetic molecular machines. Developing switchable and specifically designed crown ethers enables the implementation of function into molecular assemblies. Seven tailor-made redox-active crown ethers incorporating tetrathiafulvalene (TTF) or naphthalene diimide (NDI) as redox-switchable building blocks are described with regard to their potential to form redox-switchable rotaxanes. A combination of isothermal titration calorimetry and voltammetric techniques reveals correlations between the binding energies and redox-switching properties of the corresponding pseudorotaxanes with secondary ammonium ions. For two different weakly coordinating anions, a surprising relation between the enthalpic and entropic binding contributions of the pseudorotaxanes was discovered. These findings were applied to the synthesis of an NDI-[2]rotaxane, which retains similar spectroelectrochemical properties compared to the corresponding free macrocycle. The detailed understanding of the thermodynamic and electrochemical properties of the tailor-made crown ethers lays the foundation for the construction of new types of molecular redox switches with emergent properties.