eL-Chem Viewer: a freeware package for the analysis of electroanalytical data and their post-acquisition processing

Corrosion Behaviour of Weld Metal of Ultra-High-Strength Steel Weldments in a Sodium Chloride Aqueous Solution

As high-strength and ultra-high-strength steels are widely used in all kinds of modern welded constructions, a lot of research is carried out to investigate the mechanical properties of the weldments of these steels, but there is little information on such important characteristics as their corrosion behaviour. This research focuses on the corrosion behaviour of the weld metal of the weldments of S906QL and S700MC steels. The weld metal was tested electrochemically in a 3.5% NaCl aqueous solution via a potentiodynamic scan to determine the corrosion rate and its dependence on the welding gap. No influence of the welding gap on the corrosion rate was found, but the experimental results suggested that the corrosion rate depended on the chemical composition of the filler material and the microstructure of the weld metal.

Hexahelicene DNA-binding: Minor groove selectivity, semi-intercalation and chiral recognition

In this contribution, we focused on a fundamental study targeting the interaction of water-soluble [6]helicene derivative 1 (1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide) with double-stranded (ds) DNA. A synthetic 30-base pair duplex, plasmid, chromosomal calf thymus and salmon DNA were investigated using electrochemistry, electrophoresis and spectroscopic tools supported by molecular dynamics (MD) and quantum mechanical approaches. Both experimental and theoretical work revealed the minor groove binding of 1 to the dsDNA. Both the positively charged imidazole ring and hydrophobic part of the side chain contributed to the accommodation of 1 into the dsDNA structure. Neither intercalation into the duplex DNA nor the stable binding of 1 to single-stranded DNA were found in topoisomerase relaxation experiments with structural components of 1, i.e. [6]helicene (2) and 1-butyl-3-methylimidazolium bromide (3), nor by theoretical calculations. Finally, the binding of optically pure enantiomers (P)-1 and (M)-1 was studied using circular dichroism spectroscopy, isothermal titration calorimetry and UV Resonance Raman (UVRR) methods. Using MD and quantum mechanical methods, minor groove and semi-intercalation were proposed for compound 1 as the predominant binding modes. From the UVRR findings, we also can conclude that 1 tends to preferentially interact with adenine and guanine residues in the structure of dsDNA.

Vanadium Chloro-Substituted Schiff Base Catecholate Complexes are Reducible, Lipophilic, Water Stable, and Have Anticancer Activities

A hydrophobic Schiff base catecholate vanadium complex was recently discovered to have anticancer properties superior to cisplatin and suited for intratumoral administration. This [VO(HSHED)(DTB)] complex, where HSHED is N-(salicylideneaminato)-N'-(2-hydroxyethyl)-1,2-ethanediamine and the non-innocent catecholato ligand is di-t-butylcatecholato (DTB), has higher stability compared to simpler catecholato complexes. Three new chloro-substituted Schiff base complexes of vanadium(V) with substituted catecholates as co-ligands were synthesized for comparison with their non-chlorinated Schiff base vanadium complexes, and their properties were characterized. Up to four geometric isomers for each complex were identified in organic solvents using ⁵¹V and ¹H NMR spectroscopies. Spectroscopy was used to characterize the structure of the major isomer in solution and to demonstrate that the observed isomers are exchanged in solution. All three chloro-substituted Schiff base vanadium(V) complexes with substituted catecholates were also characterized by UV-vis spectroscopy, mass spectrometry, and electrochemistry. Upon testing in human glioblastoma multiforme (T98g) cells as an in vitro model of brain gliomas, the most sterically hindered, hydrophobic, and stable compound [t_1/2 (298 K) = 15 min in cell medium] was better than the two other complexes (IC₅₀ = 4.1 ± 0.5 μM DTB, 34 ± 7 μM 3-MeCat, and 19 ± 2 μM Cat). Furthermore, upon aging, the complexes formed less toxic decomposition products (IC₅₀ = 9 ± 1 μM DTB, 18 ± 3 μM 3-MeCat, and 8.1 ± 0.6 μM Cat). The vanadium complexes with the chloro-substituted Schiff base were more hydrophobic, more hydrolytically stable, more easily reduced compared to their corresponding parent counterparts, and the most sterically hindered complex of this series is only the second non-innocent vanadium Schiff base complex with a potent in vitro anticancer activity that is an order of magnitude more potent than cisplatin under the same conditions.

Guidelines to Study and Develop Soft Electrode Systems for Neural Stimulation

Electrical stimulation of nervous structures is a widely used experimental and clinical method to probe neural circuits, perform diagnostics, or treat neurological disorders. The recent introduction of soft materials to design electrodes that conform to and mimic neural tissue led to neural interfaces with improved functionality and biointegration. The shift from stiff to soft electrode materials requires adaptation of the models and characterization methods to understand and predict electrode performance. This guideline aims at providing (1) an overview of the most common techniques to test soft electrodes in vitro and in vivo; (2) a step-by-step design of a complete study protocol, from the lab bench to in vivo experiments; (3) a case study illustrating the characterization of soft spinal electrodes in rodents; and (4) examples of how interpreting characterization data can inform experimental decisions. Comprehensive characterization is paramount to advancing soft neurotechnology that meets the requisites for long-term functionality in vivo.

New Trimodal Phenotypic Reporter of Extended-Spectrum β-Lactamase Activity

Bacterial resistance to β-lactam antibiotics continues to grow as misadministration presents evolutionary pressure that drives bacteria to develop improved resistance enzymes. Known as extended-spectrum β-lactamases (ESBLs), these enzymes are capable of hydrolyzing advanced β-lactam antibiotics such as third-generation (and higher) cephalosporins. Phenotypic detection substrates can be used to rapidly identify a cultured patient sample prior to confirmation by more exhaustive but slower means, critically aiding in the antibiotic stewardship essential in maintaining the effectiveness of not only the cephalosporins but also indirectly the carbapenems, our last-resort β-lactams. To enhance the phenotypic detection arsenal, we have designed an ESBL detection substrate that releases a glucose molecule upon β-lactamase hydrolysis. Because many forms of detection for glucose exist, the substrate enables ESBL quantification via three modalities commonly found in the clinical laboratory: optical absorbance, for use with the most common microbiology platforms; fluorescence, for enhanced sensitivity; and electrochemistry, which offers the potential for integration into a hand-held platform similar to a personal glucometer. Moreover, we demonstrate that, as opposed to currently available phenotypic detection substrates, our new substrate is engineered to be resistant to older and narrower β-lactamases, thus enabling specific identification of newer and more dangerous ESBLs.

Self-fluorescent antibiotic MoOx-hydroxyapatite: a nano-theranostic platform for bone infection therapies

Nowadays, the repair of large-size bone defects represents a huge medical challenge. A line of attack is the construction of advanced biomaterials having multifunctional properties. In this work, we show the creation of biocompatible MoOx-hydroxyapatite nanoparticles (nano-HA/MoOx) that simultaneously exhibit self-activated fluorescence and antibiotic skills. Along this text, we demonstrate that the insertion of molybdenum, an essential trace element, into the non-stoichiometric calcium deficient hydroxyapatite lattice generates intrinsic electronic point defects that exacerbate its epifluorescence blue emission and provokes new red emissions, preserving, always, its bioactivity. Furthermore, these point defects, acting as electron acceptors, stimulate the materials' biological redox status and promote the death of pathogen microorganisms after their direct contact. A putative mechanism, by which bacteria lose electrons from their metabolic circuit that alter the function of their cytoplasmic membrane and potentially die, agrees with our results. Our findings highlight the importance of tuning the electronic communications between biomaterial interfaces and biological units, and support the use of self-fluorescent MoOx-hydroxyapatite nanoparticles as fundamental building blocks for new real-time imaging platforms against bone infection.

Novel sensor platform for rapid detection and quantification of coliforms on food contact surfaces

In this paper, a novel sensor platform based on screen printed carbon electrode coated by graphene modified polyacrylamide gel (GR/PAAGC) was developed and implemented for sampling, detection and enumeration of coliform bacteria (coliforms) on food contact surfaces. The optimized formula of polyacrylamide (PAA) and agar-agar increased the adhesive properties of the gel, being crucial for the coliforms recovery, attached to food contact surfaces. The 6-Chloro-3-indoxyl-β-D-galactopyranoside (6-CIGP) was used as a new electrochemical reporter for β-D-galactosidase activity. The released 6,6'-Dichloro-Indigo (6-DI) was directly detected by GR/PAAGC sensor. The presence of Isopropyl-β-D-thiogalactopyranoside (IPTG) and n-Octyl-β-D-thiogalactopyranoside (OBDG) in the gel contributed to reduction of the detection time. The addition of graphene enhanced the voltammetric signal and increased the conductivity of PAA gel. The anodic and cathodic peaks of the released product were directly proportional to the concentration of coliforms. Bacterial cell concentrations ranging from 1.6log₁₀CFU/mL to 6.6log₁₀CFU/mL were detected. Well-shaped, sharp voltammetric curves were generated within 3 h. Redox peaks exhibited good sensitivity with detection limits (LOD) < 0.6log₁₀CFU/mL. After series of optimization experiments, coliforms ranging from 0.6log₁₀CFU/cm² to 6.6₁₀CFU/cm² on stainless steel surfaces have been detected within 30 min with a LOD of 0.1log₁₀CFU/cm². The developed rapid, sensitive, reproducible and specific sensor successfully applied for single detection as well as for real-time monitoring of growth of coliform bacteria on stainless steel surfaces during food processing.

Electroactive Mg2+-Hydroxyapatite Nanostructured Networks against Drug-Resistant Bone Infection Strains

Surface colonization competition between bacteria and host cells is one of the critical factors involved in tissue/implant integration. Current biomaterials are evaluated for their ability both of withstanding favorable responses of host tissue cells and of resisting bacterial contamination. In this work, the antibacterial ability of biocompatible Mg²⁺-substituted nanostructured hydroxyapatite (HA) was investigated. The densities of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli strains were significantly decreased after culture in the presence of Mg-substituted HA materials in direct correlation with Mg²⁺-Ca²⁺ switch in the HA lattice. It was noticed that this decrease was accompanied by a minimal alteration of bacterial environments; therefore, the Mg²⁺-HA antibacterial effect was associated with the material surface topography and it electroactive behavior. It was observed that 2.23 wt % Mg²⁺-HA samples exhibited the best antibacterial performance; it decreased 2-fold the initial population of E. coli, P. aeruginosa, and S. aureus at the intermediate concentration (50 mg mL^-1 of broth). Our results reinforce the potential of Mg-HA nanostructured materials to be used in antibacterial coatings for implantable devices and/or medicinal materials to prevent bone infection and to promote wound healing.

The Application of Curve Fitting on the Voltammograms of Various Isoforms of Metallothioneins-Metal Complexes

The translation of metallothioneins (MTs) is one of the defense strategies by which organisms protect themselves from metal-induced toxicity. MTs belong to a family of proteins comprising MT-1, MT-2, MT-3, and MT-4 classes, with multiple isoforms within each class. The main aim of this study was to determine the behavior of MT in dependence on various externally modelled environments, using electrochemistry. In our study, the mass distribution of MTs was characterized using MALDI-TOF. After that, adsorptive transfer stripping technique with differential pulse voltammetry was selected for optimization of electrochemical detection of MTs with regard to accumulation time and pH effects. Our results show that utilization of 0.5 M NaCl, pH 6.4, as the supporting electrolyte provides a highly complicated fingerprint, showing a number of non-resolved voltammograms. Hence, we further resolved the voltammograms exhibiting the broad and overlapping signals using curve fitting. The separated signals were assigned to the electrochemical responses of several MT complexes with zinc(II), cadmium(II), and copper(II), respectively. Our results show that electrochemistry could serve as a great tool for metalloproteomic applications to determine the ratio of metal ion bonds within the target protein structure, however, it provides highly complicated signals, which require further resolution using a proper statistical method, such as curve fitting.

Novel Networked Remote Laboratory Architecture for Open Connectivity Based on PLC-OPC-LabVIEW-EJS Integration. Application in Remote Fuzzy Control and Sensors Data Acquisition

In this paper the design and implementation of a network for integrating Programmable Logic Controllers (PLC), the Object-Linking and Embedding for Process Control protocol (OPC) and the open-source Easy Java Simulations (EJS) package is presented. A LabVIEW interface and the Java-Internet-LabVIEW (JIL) server complete the scheme for data exchange. This configuration allows the user to remotely interact with the PLC. Such integration can be considered a novelty in scientific literature for remote control and sensor data acquisition of industrial plants. An experimental application devoted to remote laboratories is developed to demonstrate the feasibility and benefits of the proposed approach. The experiment to be conducted is the parameterization and supervision of a fuzzy controller of a DC servomotor. The graphical user interface has been developed with EJS and the fuzzy control is carried out by our own PLC. In fact, the distinctive features of the proposed novel network application are the integration of the OPC protocol to share information with the PLC and the application under control. The user can perform the tuning of the controller parameters online and observe in real time the effect on the servomotor behavior. The target group is engineering remote users, specifically in control- and automation-related tasks. The proposed architecture system is described and experimental results are presented.

A comparison of electrochemically pre-treated and spark-platinized carbon fiber microelectrode. Measurement of 8-oxo-7,8-dihydro-2'-deoxyguanosine in human urine and plasma

A novel method of carbon fiber microelectrode activation using spark discharge was demonstrated and compared to conventional electrochemical pretreatment by potential cycling. The spark discharge was performed at 800 V between the microelectrode connected to positive pole of the power supply and platinum counter electrode. Spark discharge led both to trimming of the fiber tip into conical shape and to the modification of carbon fiber microelectrode with platinum, as proven by scanning electron microscopy and electron dispersive X-ray spectroscopy. After the characterization of electrochemical properties using ferricyanide voltammetry, the activated electrodes were used for electrochemical analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative stress marker. Subnanomolar detection limits (0.55 nmol L(-1)) in high-performance liquid chromatography were achieved for spark platinized electrodes incorporated into the flow detection cell.