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In this study, the electrochemical mechanisms of struvite formation were investigated by studying the behavior of Mg‐based and (poly)crystalline‐Pt electrodes in the presence of ammonium dihydrogen phosphate, disodium phosphate, and ammonium chloride solutions. It was found that a precipitate was formed on the Mg‐based electrodes, while the poly‐Pt electrode showed typical voltammetric features in aqueous electrolytes. The structure, morphology, and composition of the electrochemically obtained precipitates collected from the surface of the Mg‐based electrodes were analyzed by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The results showed that the precipitate morphology was impacted by the composition of the electrolytes and the purity of the magnesium. Moreover, the Tafel kinetics and corrosion rates (vcorr) directly correlated with the electrolyte and the electrode material compositions, whereby both showed a general increase when the Mg‐based electrodes were employed in the presence of chloride anions. The Tafel slopes (β) obtained for the oxygen reduction reaction (ORR) with the poly‐Pt electrode showed a significant difference between the forward and reverse potential scans in the various electrolytes used, a finding which was mainly attributed to the adsorption of hydroxide species, alkali cations, and phosphate anions to the surface whereby these species blocked the ORR active sites. [ABSTRACT FROM AUTHOR]

Specific and sensitive electroanalysis of blood-circulating protein cancer biomarkers is often complicated by interference from serum proteins nonspecifically adsorbing at the biosensing interface and masking specific reactions of interest. Here, we have developed an electrocatalytically amplified assay for specific and sensitive analysis of human epidermal growth factor receptor-2 (HER-2/ neu, a protein cancer biomarker over-expressed in breast cancers) that allows us to avoid both the interference from bovine serum albumin (BSA) and electrocatalytic amplification of the signal stemming from the specific aptamer−HER-2/ neu binding. A HER-2/ neu-specific thiolated aptamer sequence was co-adsorbed on gold together with a C11 alkanethiol bearing two ethylene glycol (EG)2 head groups that prevented non-specific adsorption of BSA. On such layers, electrochemical reduction of a ferricyanide redox indicator is inhibited and is shown to be electrocatalyzed by methylene blue electrostatically interacting with negatively charged HER-2/ neu. The electrocatalytic signal increased upon HER-2/ neu binding to the aptamer, which allowed 10−12-10−8 M HER-2/ neu detection in 1 % serum, being practically applicable for clinical testing. The developed strategy can be considered as general and applicable for the electroanalysis of other blood-circulating proteins once the electrostatic compatibility between the protein and redox probe is established. [ABSTRACT FROM AUTHOR]

The fabrication of a planar micro electrochemical cell is presented. The simplicity and the relative low cost of this kind of cells make them very interesting and promising in the development of chemical and biochemical sensors. The utilization of microelectrodes as working electrodes in planar electrochemical cells is preferred to the conventional macro electrodes because microelectrodes can be used in highly resistive media, have short response time, and excellent signal to noise ratio. In electrochemical sensor applications, the microelectrode surfaces are commonly modified with multiple layers to boost selectivity, control sensitivity, or to provide a biocompatible interface between the sensor and its environment. In this work, the fabricated set of bundled electrodes is covered with a hydrogel as an example of its potential use as electrochemical gas sensor. All micro electrochemical cells were characterized by cyclic voltammetry (CV) and the results were analyzed with different statistical methods. [ABSTRACT FROM AUTHOR]

Electrical properties of self-assembling DNA nanostructures underlie the paradigm of nanoscale bioelectronics, and as such require clear understanding. DNA-mediated electron transfer (ET) from a gold electrode to DNA-bound Methylene Blue (MB) shows directional preference, and it is sequence-specific. During the electrocatalytic reduction of [Fe(CN) 6 ] 3- catalyzed by DNA-bound MB, the ET rate constant for DNA-mediated reduction of MB reaches (1.32±0.2)10 3 and (7.09±0.4)10 3  s -1 for (dGdC) 20 and (dAdT) 25 duplexes. The backward oxidation process is less efficient, making the DNA duplex a molecular rectifier. Lower rates of ET via (dGdC) 20 agree well with its disturbed π-stacked sub-molecular structure. Such direction- and sequence-specific ET may be implicated in DNA oxidative damage and repair, and be relevant to other polarized surfaces, such as cell membranes and biomolecular interfaces., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrical properties of DNA critically depend on the way DNA molecules are integrated within the electronics, particularly on DNA-electrode immobilization strategies. Here, we show that the rate of electron transport in DNA duplexes spacer-free tethered to gold via the adenosine terminal region (a dA 10 tag) is enhanced compared to the hitherto reported DNA-metal electrode tethering chemistries. The rate of DNA-mediated electron transfer (ET) between the electrode and methylene blue intercalated into the dA 10 -tagged DNA duplex approached 361 s -1 at a ca. half-monolayer DNA surface coverage Γ DNA (with a linear regression limit of 670 s -1 at Γ DNA → 0), being 2.7-fold enhanced compared to phosphorothioated dA 5 * tethering (6-fold for the C 6 -alkanethiol linker representing an additional ET barrier). X-ray photoelectron spectroscopy evidenced dA 10 binding to the Au surface via the purine N, whereas dA 5 * predominantly coordinated to the surface via sulfur atoms of phosphothioates. The latter apparently induces the DNA strand twist in the point of surface attachment affecting the local DNA conformation and, as a result, decreasing the ET rates through the duplex. Thus, a spacer-free DNA coupling to electrodes via dA 10 tags thus allows a perspective design of DNA electronic circuits and sensors with advanced electronic properties and no implication from more expensive, synthetic linkers.