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Electrochemical devices have received particular attention due to their rapid detection and great sensitivity for the evaluation of DNA-hazard compounds interaction mechanisms. Several types of bioanalytical method use nucleic acids probes to detect DNA damage. This article reviews current directions and strategies in the development and applications of electrochemical DNA sensors for the detection of DNA damage.

Natural phenolic compounds are abundant in the vegetable kingdom, occurring mainly as secondary metabolites in a wide variety of chemical structures. Around 10,000 different plant phenolic derivatives have been isolated and identified. This review provides an exhaustive overview concerning the electron transfer reactions in natural polyphenols, from the point of view of their in vitro antioxidant and/or pro‐oxidant mode of action, as well as their identification in highly complex matrixes, for example, fruits, vegetables, wine, food supplements, relevant for food quality control, nutrition, and health research. The accurate assessment of polyphenols’ redox behavior is essential, and the application of the electrochemical methods in routine quality control of natural products and foods, where the polyphenols antioxidant activity needs to be quantified in vitro, is of the utmost importance. The phenol moiety oxidation pathways and the effect of substituents and experimental conditions on their electrochemical behavior will be reviewed. The fundamental principles concerning the redox behavior of natural polyphenols, specifically flavonoids and other benzopyran derivatives, phenolic acids and ester derivatives, quinones, lignins, tannins, lignans, essential oils, stilbenes, curcuminoids, and chalcones, will be described. The final sections will focus on the electroanalysis of phenolic antioxidants in natural products and the electroanalytical evaluation of in vitro total antioxidant capacity.

Palladium nanoparticles and nanowires electrochemically deposited onto a carbon surface were studied using cyclic voltammetry, impedance spectroscopy and atomic force microscopy. The ex situ and in situ atomic force microscopy (AFM) topographic images showed that nanoparticles and nanowires of palladium were preferentially electrodeposited to surface defects on the highly oriented pyrolytic graphite surface and enabled the determination of the Pd nanostructure dimensions on the order of 50-150 nm. The palladium nanoparticles and nanowires electrochemically deposited onto a glassy carbon surface behave differently with respect to the pH of the electrolyte buffer solution. In acid or mild acid solutions under applied negative potential, hydrogen can be adsorbed/absorbed onto/into the palladium lattice. By controlling the applied negative potential, different quantities of hydrogen can be incorporated, and this process was followed, analysing the oxidation peak of hydrogen. It is also shown that the growth of the Pd oxide layer begins at negative potentials with the formation of a pre-monolayer oxide film, at a potential well before the hydrogen evolution region. At positive potentials, Pd(0) nanoparticles undergo oxidation, and the formation of a mixed oxide layer was observed, which can act as nucleation points for Pd metal growth, increasing the metal electrode surface coverage. Depending on thickness and composition, this oxide layer can be reversibly reduced. AFM images confirmed that the PdO and PdO 2 oxides formed on the surface may act as nucleation points for Pd metal growth, increasing the metal electrode surface coverage.

G-rich oligodeoxynucleotides (ODNs) have great medical and nanotechnological potential, because they can self-assemble into G-quadruplexes and higher-order nanostructures. The folding properties of d(G)10, d(TG9) and d(TG8T) ODNs were studied using atomic force microscopy (AFM) and voltammetry at carbon electrodes. Single-stranded ODNs, in Na(+) containing solutions and for short incubation times, were detected using AFM as network films and polymeric structures and using voltammetry by the occurrence of only the guanine oxidation peak. G-quadruplexes, in Na(+) containing solutions and long incubation times, or in K(+) containing solutions, were detected using AFM as spherical aggregates and using voltammetry by the decrease of the guanine oxidation peak and the occurrence of the G-quartet oxidation peak. Concerning the self-assembling into higher-order nanostructures, d(G)10 was the only sequence forming G-nanowires observed using AFM, d(TG9) formed short G-based super-structures that adsorbed as rod-like shape aggregates, and d(TG8T) formed no nanostructures, due to the presence of thymine residues at both 5' and 3' ends.

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Glassy carbon electrodes (GCE) were modified with poly(glutamic acid) acid films prepared using three different procedures: glutamic acid monomer electropolymerization (MONO), evaporation of poly(glutamic acid) (PAG) and evaporation of a mixture of poly(glutamic acid)/glutaraldehyde (PAG/GLU). All three films showed good adherence to the electrode surface. The performance of the modified GCE was investigated by cyclic voltammetry and differential pulse voltammetry, and the films were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The three poly(glutamic acid) modified GCEs were tested using the electrochemical oxidation of ascorbic acid and a decrease of the overpotential and the improvement of the oxidation peak current was observed. The PAG modified electrode surfaces gave the best results. AFM morphological images showed a polymeric network film formed by well-defined nanofibres that may undergo extensive swelling in solution, allowing an easier electron transfer and higher oxidation peaks.