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Using graphene oxide (GO)‐loaded Fe3O4‐Pd‐Ag (GO/Fe3O4‐Pd‐Ag) nanoparticles on a gold electrode as a platform, an unlabeled electrochemical immunosensor was fabricated in this study to detect the carcinoembryonic antigen (CEA) with high sensitivity. After modification, the stability and strength of the signal are improved by the increased effective area of the electrode and the synergistic effect of the silver nanoparticles with GO, Fe3O4, and Pd. The signal intensity decreased as the concentration of CEA increased. Using cyclic voltammetry and electrochemical impedance spectroscopy, the immunosensor layer assembly process was validated. Under optimal conditions, the electrochemical immunosensor had a detection range of 1 pg mL−1 to 80 ng mL−1. The linear equation was I (μA)=304.563–41.867×logcCEA (ng mL−1), the correlation coefficient was 0.9967, and the detection limit was 0.2 pg mL−1. In addition, the modified electrochemical immunosensor exhibited high selectivity, stability, and repeatability. This electrochemical immunosensor shows a good application prospect in the detection of tumor marker CEA. [ABSTRACT FROM AUTHOR]

The molecular conductance of 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyano-quinodimethane (F4TCNQ) with different electronic states (neutral, radical anion, and dianion) was investigated by the scanning tunneling microscope break junction (STM-BJ) technique. These electronic states have distinct conductance, and the conductance decreases in the order of neutral > radical anion > dianion. Surprisingly, the molecular conductance of the neutral F4TCNQ junction reaches 10−1.17G0, attributed to its LUMO energy level being close to the Fermi level of the gold electrode. Moreover, we found that neutral F4TCNQ can be gradually reduced to radical anions under a relatively low bias voltage of 100 mV. These results will advance the development of organic optoelectronic devices and molecule electronics. [ABSTRACT FROM AUTHOR]

Heavy metal ions can have a negative impact on human health when they are present in the environment and diet. In order to enhance healthcare globally, simple, dependable, sensitive, rapid, and accurate technologies for their detection must be created. Herein, we report a sol-gel preparation of nickel oxide (NiO) nanoparticles. The prepared NiO nanoparticles are extensively characterized by PXRD, SEM, and EDS approaches. The obtained SEM results showed that NiO has a nanosphere-shaped surface morphology. The surface area of a gold electrode (Au) was fabricated with NiO nanoparticles via the drop-casting method. The fabricated electrode with NiO nanoparticles (NiO/Au) was applied as an arsenic sensor. The NiO/Au exhibits decent sensitivity of 3.10 µA/ppb and a limit of detection of 1.94 ppb. The NiO/Au also shows good sensing performance for arsenic detection, which includes good stability, repeatability, and selectivity. So far, this is the first report which adopted two electrochemical techniques (cyclic voltammetry and linear sweep voltammetry) for the detection of arsenic using NiO/Au. [ABSTRACT FROM AUTHOR]

Polymeric coatings of styrene derivatives due to its ease of production and application have been employed in fascinating range of applications. Distinct from other polymerization techniques, electrodeposition offers as a convenient strategy to achieve strong adherence between the polymer films and electrode surfaces which is highly desirable for functional coatings. In this study, it was aimed to electrosynthesize and characterize the functional polymer, poly (4-amino-3-nitrostyrene), for the first time. Electrosynthesis from 4-amino-3-nitrostyrene monomer onto gold electrodes was investigated in 0.1 M tetrabutyl ammonium perchlorate/dichloromethane solution. Cathodic electropolymerization was performed by cyclic voltammetry (CV) with a potential range of 0.4 V to − 2.0 V vs. SCE. The properties of the obtained polymeric coatings were investigated via electrochemical, microscopic and spectrochemical methods. The redox and charge transfer resistance behaviour of the resulting polymer was examined via CV and electrochemical impedance spectroscopy (EIS) measurements. Spectroscopic (UV–Vis, ATR-FTIR) techniques were employed to distinguish between the monomer and the obtained polymer film. The polymeric film thickness was measured by an optical profilometer and the optical energy gap of the obtained film was 2.41 eV. Scanning electron microscopy characterization of the polymer on the substrate revealed a compact film structure. Contact angle measurements displayed the low wettability of the polymer. Due to the good adhesion of the coatings, its usability for future corrosion protection studies was examined via EIS measurements. Electropolymerized poly (4-amino-3-nitrostyrene) showed a good potential to be used as a corrosion protection coating material since it preserved a long-term corrosion resistance. [ABSTRACT FROM AUTHOR]

Food contamination by aflatoxins is an urgent global issue due to its high level of toxicity and the difficulties in limiting the diffusion. Unfortunately, current detection techniques, which mainly use biosensing, prevent the pervasive monitoring of aflatoxins throughout the agri-food chain. In this work, we investigate, through ab initio atomistic calculations, a pyrrole-based Molecular Field Effect Transistor (MolFET) as a single-molecule sensor for the amperometric detection of aflatoxins. In particular, we theoretically explain the gate-tuned current modulation from a chemical–physical perspective, and we support our insights through simulations. In addition, this work demonstrates that, for the case under consideration, the use of a suitable gate voltage permits a considerable enhancement in the sensor performance. The gating effect raises the current modulation due to aflatoxin from 100% to more than 10 3 ÷ 10 4 %. In particular, the current is diminished by two orders of magnitude from the μA range to the nA range due to the presence of aflatoxin B1. Our work motivates future research efforts in miniaturized FET electrical detection for future pervasive electrical measurement of aflatoxins. [ABSTRACT FROM AUTHOR]

An ultrasensitive electrochemical DNA sensor was designed for Hg2+ assay using cooperative signal amplification effect of electrodeposited Au/carbon nanofibers‐chitosan (DpAu/CNFs‐CS) and reduced graphene oxide (RGO). CNFs‐CS was prepared to modify gold electrode (AuE). Then, Au was electrodeposited on CNFs‐CS/AuE to form DpAu/CNFs‐CS/AuE for the first signal amplification. With TH as signal probe and ssDNA as recognition component, RGO/ssDNA and RGO/TH interaction were used for the second signal amplification. The prepared sensor had wider linear range of 0.0001–460 nM and lower detection limit of 5.7×10−5 nM, high selectivity, and performed well in Hg2+ assay of tap water. [ABSTRACT FROM AUTHOR]

A convenient assembly recently proposed for screen printed gold electrodes (SPEs) suitable for measurements in gaseous samples is here tested for the analysis of the ethanol content in alcoholic drinks. This assembly involves the use of a circular crown of filter paper, soaked in the room temperature ionic liquid (RTIL) 1‐butyl‐3‐methylimidazolium hydrogen sulfate, which is simply placed upon a disposable screen printed cell, so as to contact the outer edge of the gold disc working electrode, as well as peripheral counter and reference electrodes. The electrical contact between the paper crown soaked in RTIL and the SPE electrode is assured by a gasket and all components are installed in a polylactic acid holder. This assembly provides a portable and disposable electrochemical platform, assembled by the easy immobilization onto a porous and inexpensive supporting material such as paper of a RTIL characterized by profitable electrical conductivity and negligible vapor pressure. The electroanalytical performance of this device was assayed for the flow injection analysis of the ethanol concentration in some real samples of wine and beer and the results obtained are compared with the alcoholic degree reported in the relevant bottle‐labels, thus highlighting a substantially satisfactory agreement. Repeatable sharp peaks (RSD=6–8 %) were detected for ethanol over a wide linear range (1–20 % v/v in water) and a detection and quantitation limit of 0.55 % v/v and 1.60 % v/v were inferred for a signal‐to‐noise ratio of 3 and 10, respectively. [ABSTRACT FROM AUTHOR]

A rapid method for determination of hydrogen peroxide based on a non‐enzymatic amperometric sensor with an online dialysis unit was developed for analysis of sample with complicated matrices. A porous gold modified gold screen‐printed electrode was prepared by a simple method using 9 V‐battery electrodeposition. Based on data from amperometry, a linear dynamic range can be obtained in the range of 10 to 1000 μmol L−1, with a limit of detection of 0.37 μmol L−1. The proposed system was successfully applied to determine H2O2 in various milk samples with rapid analysis, high electrode stability, and excellent repeatability (1.95 % RSD with 100 replications). [ABSTRACT FROM AUTHOR]

Fermi's golden rule, a remarkable concept for the transition probability involving continuous states, is applicable to the interfacial electron‐transporting efficiency via correlation with the surface density of states (SDOS). Yet, this concept has not been reported to tailor single‐molecule junctions where gold is an overwhelmingly popular electrode material due to its superior amenability in regenerating molecular junctions. At the Fermi level, however, the SDOS of gold is small due to its fully filled d‐shell. To increase the electron‐transport efficiency, herein, gold electrodes are modified by a monolayer of platinum or palladium that bears partially filled d‐shells and exhibits significant SDOS at the Fermi energy. An increase by 2–30 fold is found for single‐molecule conductance of α,ω‐hexanes bridged via common headgroups. The improved junction conductance is attributed to the electrode self‐energy which involves a stronger coupling with the molecule and a larger SDOS participated by d‐electrons at the electrode‐molecule interfaces. [ABSTRACT FROM AUTHOR]

The concentration of human immunoglobulin E (IgE) in blood is an indicator for diagnosing an allergy. For detecting human IgE by an electrochemical immunosensor, redox mediator molecules were modified on a gold electrode using thiolated organic molecules, which can form self‐assembled monolayers on the electrode surface. Ferrocene was used as a redox mediator, and the current signal was amplified via redox cycling using 4‐aminophenol. Measurements were obtained after the immobilization of the target‐captured antibody, target human IgE, biotin‐conjugated secondary antibody, and avidin alkaline phosphatase in a sandwich‐type immunosensor configuration. The prepared immunosensor exhibited a limit of detection of 1 IU/mL and dynamic range of 3–30 IU/mL. [ABSTRACT FROM AUTHOR]

Flexible, wearable biosensors have been extensively investigated in recent decades due to their potential applications in portable electronics and human health monitoring. However, low sensitivity and complex fabrication are still great challenges for flexible sensors. Herein, a flexible electrochemical biosensor for glucose was proposed, which was based on reduced graphene oxide and gold nanoparticle-modified screen-printed gold electrodes (rGO-Au/SPGE) as catalysts and gel instead of traditional liquid electrolyte. The biosensor combines the soft stretchability of the gel, the specific selectivity of glucose oxidase (GOx) and the high catalytic activity of the rGO-Au/SPGE nanocomposite. More importantly, the soft gel not only adheres well to the skin, but also promotes the penetration of water-soluble molecules, effectively improving the accumulation of bodily fluids on dry skin surfaces. The constructed GOx-gel-rGO-Au/SPGE biosensor maintains stable sensing performance even after 1000 bending cycles. In addition, the biosensor exhibited significantly current response to glucose at a detection range of 1.25–850 µM and 0.85–7.72 mM (covers the glucose level in human sweat), with a sensitivity of 53.7 and 27.4 μA/mM cm2 and low detection limit (1.25 µM). The flexible electrochemical biosensor based on GOx-gel-rGO-Au/SPGE could accurately determine glucose in human sweat, demonstrating a promising feature for personal healthcare diagnosis. [ABSTRACT FROM AUTHOR]

In addition to the classic functions of proteins, such as acting as a biocatalyst or binding partner, the conformational states of proteins and their remodeling upon stimulation need to be considered. A prominent example of a protein that undergoes comprehensive conformational remodeling is transglutaminase 2 (TGase 2), the distinct conformational states of which are closely related to particular functions. Its involvement in various pathophysiological processes, including fibrosis and cancer, motivates the development of theranostic agents, particularly based on inhibitors that are directed toward the transamidase activity. In this context, the ability of such inhibitors to control the conformational dynamics of TGase 2 emerges as an important parameter, and methods to assess this property are in great demand. Herein, we describe the application of the switchSENSE® principle to detect conformational changes caused by three irreversibly binding Nε-acryloyllysine piperazides, which are suitable radiotracer candidates of TGase 2. The switchSENSE® technique is based on DNA levers actuated by alternating electric fields. These levers are immobilized on gold electrodes with one end, and at the other end of the lever, the TGase 2 is covalently bound. A novel computational method is introduced for describing the resulting lever motion to quantify the extent of stimulated conformational TGase 2 changes. Moreover, as a complementary biophysical method, native polyacrylamide gel electrophoresis was performed under similar conditions to validate the results. Both methods prove the occurrence of an irreversible shift in the conformational equilibrium of TGase 2, caused by the binding of the three studied Nε-acryloyllysine piperazides. [ABSTRACT FROM AUTHOR]

Recent developments in embedded electronics require the development of micro sources of energy. In this paper, the fabrication of an on-chip interdigitated all-solid-state supercapacitor, using porous gold electrodes and a PVA/KOH quasisolid electrolyte, is demonstrated. The fabrication of the interdigitated porous gold electrode is performed using an original bottom-up approach. A templating method is used for porosity, using a wet chemistry process followed by microfabrication techniques. This paper reports the first example of an all-gold electrode micro-supercapacitor. The supercapacitor exhibits a specific capacitance equal to 0.28 mF·cm−2 and a specific energy of 0.14 mJ·cm−2. The capacitance value remains stable up to more than 8000 cycles. [ABSTRACT FROM AUTHOR]

The biosensing of bacterial pathogens is of a high priority. Electrochemical biosensors are an important future tool for rapid bacteria detection. A monolayer of bacterial-binding peptides can serve as a recognition layer in such detection devices. Here, we explore the potential of random peptide mixtures (RPMs) composed of phenylalanine and lysine in random sequences and of controlled length, to form a monolayer that can be utilized for sensing. RPMs were found to assemble in a thin and diluted layer that attracts various bacteria. Faradaic electrochemical impedance spectroscopy was used with modified gold electrodes to measure the charge-transfer resistance (RCT) caused due to the binding of bacteria to RPMs. Pseudomonas aeruginosa was found to cause the most prominent increase in RCT compared to other model bacteria. We show that the combination of highly accessible antimicrobial RPMs and electrochemical analysis can be used to generate a new promising line of bacterial biosensors. [ABSTRACT FROM AUTHOR]

The adsorption of analyte molecules on nano-optoelectrodes (e.g. a combined nanoantenna and nanoelectrode device) significantly affects the signal characteristics in surface-enhanced Raman scattering (SERS) measurements. Understanding how different molecules adsorb on electrodes and their electrical potential modulation helps interpret SERS measurements better. We use molecular dynamics simulations to investigate the adsorption of prototypical analyte molecules (rhodamine 6G and choline) on gold electrodes with negative, neutral, and positive surface charges. We show that both molecules can readily adsorb on gold surfaces at all surface charge densities studied. Nevertheless, the configurations of the adsorbed molecules can differ for different surface charge densities, and adsorption can also change a molecule’s conformation. Rhodamine 6G molecules adsorb more strongly than choline molecules, and the adsorption of both molecules is affected by electrode charge in 0.25 M NaCl solutions. The mechanisms of these observations are elucidated, and their implications for voltage-modulated SERS measurements are discussed. [ABSTRACT FROM AUTHOR]

In this review, functionalized nanogaps embedded in nanopores are discussed in view of their high biosensitivity in detecting biomolecules, their length, type, and sequence. Specific focus is given on nanoelectrodes functionalized with tiny nanometer‐sized diamond‐like particles offering vast functionalization possibilities for gold junction electrodes. This choice of the functionalization, in turn, offers nucleotide‐specific binding possibilities improving the detection signals arising from such functionalized electrodes potentially embedded in a nanopore. The review sheds light onto the use and enhancement of the tunnelling recognition in functionalized nanogaps towards sensing DNA nucleotides and mutation detection, providing important input for a practical realization. [ABSTRACT FROM AUTHOR]

A new aptasensor for detecting fumonisin B1 (FB1) in the maize samples was developed based on DNA- aptamer recognition and electrochemical technique. A thiol-modified single-stranded DNA (ss-HSDNA) was immobilized on a screen printed carbon electrode (SPCE) electrodeposited by gold nanoparticles (AuNPs). The morphology and structure of SPCE and AuNPs/SPCE were evaluated via scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The SEM results demonstrated that the SPCE had a flat sheet-like structure, and the AuNPs were homogeneously electrodeposited on the SPCE. Cyclic voltammetry (CV) experiments in the [Fe(CN)6]− 3/− 4 solution were conducted to investigate each step of electrode modification as well as aptasensor performance. Aptamer-FB1 interaction prevented the electron transfer permitting the determination of FB1 in the range of 0.5–500 ng/mL with a low detection limit (0.14 ng/mL). The designed aptasensor was also shown high selectivity, acceptable repeatability and reproducibility, good long-term stability, and excellent recovery. Furthermore, there was a strong correlation between the findings achieved via the designed aptasensor and high performance liquid chromatography (HPLC). Therefore, a simple construction process and satisfactory electrochemical performance of the proposed aptasensor have a great potential for the detection of FB1 in maize samples. [ABSTRACT FROM AUTHOR]

Two electrochemical bioplatforms were prepared based on thiolated hairpin DNA probes tethered to AuNP-modified screen-printed electrodes to detect T > G and T > C polymorphisms, namely rs1880269 and rs1800469, present the interleukin-6 (IL6) and transforming growth factor β1 (TGFβ1) genes. The electrochemical readout was ensured by the detection of the double-stranded DNA using methylene blue as a redox probe after treatment by EcoRI restrictase. The main parameters influencing the analytical response such as the thiolated DNA probe concentration, incubation time with electrode, DNA hybridization time, EcoRI enzyme load, and its cleavage time were optimized based on the current intensity and signal-to-blank (S/B) ratio as selection criteria. Using spiked buffer solutions, the IL6 and TGFβ1 E-bioplatforms display wide ranges of linearity (1 × 102–1 × 108 fM and 5 × 101–1 × 105 fM, respectively) and limits of detection (47.9 fM and 16.6 fM, respectively). The two bioelectrodes have also good discrimination toward 1-mismatched, two mismatched, and non-complementary sequences, when they were used 30-fold higher than the target sequences. More importantly, the two bioplatforms successfully detected the single nucleotide polymorphisms (SNPs) in scarcely diluted genomic DNA, collected from 52 donors, and showed they can reliably distinguish between heterozygous (TG and TC genotypes) and homozygous (GG and CC genotypes) patients with respect to the control subjects (TT genotype), where the differences are statistically highly significant (p-value < 0.0001). Thus, the designed devices could be used to conduct large cohort studies targeting these mutations or extended to other SNPs. [ABSTRACT FROM AUTHOR]

In this study, polypyrrole-based molecularly imprinted polymer (MIP) containing phosphate selective site as a conductive polymer material for phosphate ion sensor was successfully synthesized and characterized. The synthesis of MIP-phosphate was carried out using pyrrole as a functional monomer by cyclic voltammetry on the surface of gold wire electrode. The MIP-phosphate electropolymerization was performed in potential range from −0.8 to 0.6 V at a scan rate of 100 mV/s for 10 cycles. According to the FTIR spectra and visual observation of SEM images, the MIP-phosphate was successfully synthesized as a homogenous and well-ordered porous structure. The MIP electrode response to phosphate was examined by potentiometry method, showing an excellent linear response for , , and within the concentration range of 1 × 10–7 to 0.1 M with good sensitivity. The selectivity coefficient result also indicates good selectivity toward phosphate ions against the interfering anions (Cl–, , and ). [ABSTRACT FROM AUTHOR]

Studies of electrosensory systems have led to insights into a number of general issues in biology. However, investigations of these systems have been limited by the inability to precisely control spatial patterns of electrosensory input. In this paper, an electrode array and a system to selectively stimulate spatially restricted regions of an electroreceptor array are presented. The array has 96 channels consisting of chrome/gold electrodes patterned on a flexible parylene‐C substrate and encapsulated with another parylene‐C layer. The conformability of the electrode array allows for optimal current driving and surface interface conditions. Recordings of neural activity at the first central processing stage in weakly electric mormyrid fish support the potential of this system for high spatial resolution stimulation and mapping of electrosensory systems. [ABSTRACT FROM AUTHOR]

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Sweat-rate measurement has received more and more attention, especially for specific groups, such as athletes, soldiers and manual workers, due to their excessive sweat loss under prolonged intense heat stress, which increases the risk of dehydration and electrolyte imbalance. The highly effective manufacture of a sweat-sensing device is essential to its wide range of applications in perspiration-related physiological information detection. In this work, we propose a simple and cost-effective strategy for the manufacture of a microfluidic sweat-rate-sensing patch via laser cutting and transfer printing technology. A copper foil tape is used as the electrode for in situ admittance based sweat-rate-sensing. The detection circuits and measurement conditions are optimized to prevent the negative effect of an electrochemical reaction between a copper electrode and sweat for precise admittance measurement. In vitro and on-body experiments demonstrate that the copper electrode is applicable for admittance-based sweat sensing and is capable of achieving equivalent sensing accuracy as a gold electrode and that the proposed sensor structure can perform consecutive and accurate sweat-rate-sensing and facilitates a significant increase in manufacturing efficiency. [ABSTRACT FROM AUTHOR]

In this work, a novel sandwich-type electrochemical immunosensor was developed for the quantitative detection of the carcinoembryonic antigen, an important tumor marker in clinical tests. The capture antibodies were immobilized on the surface of a gold disk electrode, while detection antibodies were attached to redox-tagged single-walled carbon nanohorns/thionine/AuNPs. Both types of antibody immobilization were carried out through Au-S bonds using the novel photochemical immobilization technique that ensures control over the orientation of the antibodies. The electroactive SWCNH/Thi/AuNPs nanocomposite worked as a signal tag to carry out both the detection of carcinoembryonic antigen and the amplification of the detection signal. The current response was monitored by differential pulse voltammetry. A clear dependence of the thionine redox peak was observed as a function of the carcinoembryonic antigen concentration. A linear detection range from 0.001–200 ng/mL and a low detection limit of 0.1385 pg/mL were obtained for this immunoassay. The results showed that carbon nanohorns represent a promising matrix for signal amplification in sandwich-type electrochemical immune assays working as a conductive and binding matrix with easy and versatile modification routes to antibody and redox tag immobilization, which possesses great potential for clinical diagnostics of CEA and other biomarkers. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is one of the foodborne pathogenic bacteria that greatly threatens human health. An ultrasensitive technology for P. aeruginosa detection is urgently demanded. Herein, based on the mechanism of aptamer-specific recognition, an electrochemical-colorimetric dual-mode ultrasensitive sensing strategy for P. aeruginosa is proposed. The vertices of DNA tetrahedral nanoprobes (DTNPs), that immobilized on the gold electrode were modified with P. aeruginosa aptamers. Furthermore, the G-quadruplex, which was conjugated with a P. aeruginosa aptamer, was synthesized via rolling circle amplification (RCA). Once P. aeruginosa is captured, a hemin/G-quadruplex, which possesses peroxidase-mimicking activity, will separate from the P. aeruginosa aptamer. Then, the exfoliated hemin/G-quadruplexes are collected for oxidation of the 3,3′,5′,5′-tetramethylbenzidine for colorimetric sensing. In the electrochemical mode, the hemin/G-quadruplex that is still bound to the aptamer catalyzes polyaniline (PANI) deposition and leads to a measurable electrochemical signal. The colorimetric and electrochemical channels demonstrated a good forward and reverse linear response for P. aeruginosa within the range of 1–108 CFU mL−1, respectively. Overall, compared with a traditional single-mode sensor for P. aeruginosa, the proposed dual-mode sensor featuring self-calibration not only avoids false positive results but also improves accuracy and sensitivity. Furthermore, the consistency of the electrochemical/colorimetric assay was verified in practical meat samples and showed great potential for applications in bioanalysis. [ABSTRACT FROM AUTHOR]

In this work, we simulated the smallest fullerene molecule, C20 in a two-probe device model with gold electrodes. The gold electrodes comprised of (011) miller planes were carved to construct the novel geometry based four unique shapes, which were strung to fullerene molecules through mechanically controlled break junction techniques. The organized devices were later scrutinized using non-equilibrium Green's function based on the density functional theory to calculate their molecular orbitals, energy levels, charge transfers, and electrical parameters. After intense scrutiny, we concluded that five-edged and six-edged devices have the lowest and highest current-conductance values, which result from their electrode-dominating and electrode-subsidiary effects, respectively. However, an interesting observation was that the three-edged and four-edged electrodes functioned as semi-metallic in nature, allowing the C20 molecule to demonstrate its performance with the complementary effect of these electrodes in the electron conduction process of a two-probe device. [ABSTRACT FROM AUTHOR]

In this work, we describe a new type of electrochemical aptasensor for the label-free detection of oxytetracycline (OTC). Thin-film gold electrodes were fabricated through sputtering gold on a Kapton film, followed by the immobilization of a thiol-modified aptamer on the electrode surface. The selective capture of OTC at the aptamer-functionalized electrodes was monitored electrochemically with the use of the [Fe(CN)6]4−/[Fe(CN)6]3− redox probe. Different experimental variables were studied, through which the metrological features for OTC determination were derived. Finally, the developed sensor was implemented to achieve the detection of OTC in a spiked milk sample.

Hydrophobins are proteins, consisting of approximately 70–130 amino acids and containing eight cysteines, linked by four disulfide bonds, which are characteristic of the entire hydrophobin family. The main advantage of hydrophobins is their ability to form amphiphatic layers on surfaces and thus to change their properties from hydrophilic to hydrophobic and vice versa. It is for this reason that hydrophobins can be widely used in a variety of applications to improve the properties of materials, such as hydrophilicity, activity and stability of immobilized molecules. In this work, the hydrophobin RodA of Aspergillus fumigatus and its properties were investigated. The gene responsible for the synthesis of the RodA protein was identified by molecular biology methods and used to design an expression system. The purified recombinant RodA protein was used to modify the surface of a gold electrode in order to investigate the effect of this hydrophobin as a matrix on the performance of the engineered glucose biosensor. The engineered biosensor with the RodA matrix was compared with a biosensor without the RodA matrix. The data obtained were fitted to Michaelis–Menten and linear models to calculate the KM and the maximum current generated (Imax). In the case of Au/GOx, the KM value was 6.99 mM and the Imax was 34.8 μA·cm−2; in the case of the Au/RodA/GOx biosensor, the KM value was 2.37 mM and the Imax was 0.432 μA·cm−2. The lower Imax value for the Au/RodA/GOx biosensor could be explained by the possible formation of an excessively thick monolayer of RodA protein or by possible conformations of the protein that blocked the glucose oxidase molecules. However, the KM value obtained for Au/RodA/GOx showed that for this biosensor, the immobilized glucose oxidase has a significantly higher affinity for the substrate, indicating that such a protein may be suitable for electrode modifications. [ABSTRACT FROM AUTHOR]

A powder of titanium oxide nanoparticles (TiO2 NPs) was synthesized in this study by anodizing in 0.7 M HClO4 and then annealing in N2 at 450 °C for 3 h to produce TiO2 NPs-N2 powder as a catalyst. These TiO2 NPs-N2 nanoparticles were then encrusted with Au nanoparticles utilizing the photodeposition procedure with tetrachloroauric acid (HAuCl4) and isopropanol as sacrificial donors. With a surface area of 121 m2g−1, the Au NPs/TiO2 NPs-N2 powder catalyst has a high surface area, according to the Barrett–Joyner–Halenda technique. According to X-ray diffraction (XRD) analysis, TiO2 NPs-N2 contained uniformly integrated Au nanoparticles with an average crystallite size of about 26.8 nm. The XRD patterns showed that the prepared Au NPs/TiO2 NPs-N2 were crystallites and nano-sized. The transmission electron microscopy image revealed the spherical shape of the nanoparticles and their tendency for agglomeration. Utilizing the cyclic voltammetry, the electrochemical properties of the catalyst TiO2 NPs powders in a basic glucose solution were investigated. The electrocatalytic activity and stability of the loaded Au NPs/TiO2 NPs-N2 powder on the working electrode for the electrocatalytic oxidation of glucose were astonishingly high. The Au NPs/TiO2 NPs-N2 catalyst demonstrated electrocatalytic characteristics that were superior to a commercially available polycrystalline gold electrode in the application involving glucose alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Amyloid-β oligomers (AβOs) was the core-biomarker of Alzheimer's disease (AD), and the detection of AβOs is very important for the early diagnosis of AD. However, existing tests for AβOs are majorly suffering from complex process and poor sensitivity. Thus, an adjustable AβOs electrochemiluminescence (ECL) aptasensor based on the synergistic effect of self-enhanced metal-organic gel (AgCNS) and triple-helix DNA system (THS) was successfully constructed. AgCNS was prepared by an extremely simple one-pot method and was an innovative luminophore with excellent ECL performance. The AgCNS-labeled complementary sequence (AgCNS@CP) was interlaced with the unlabeled aptamer (Apt) carrying two short-arms fixed on the gold electrode (GE) to form the THS. Along with the specific-binding of AβOs and Apt, the THS was disrupted and adjusted flexibly between "on" and "off", resulting in significant changes in the ECL signals. Thus, ECL detection of AβOs was sensitively achieved with a detection limit as low as 0.23 fM and the different forms of Aβ can be specifically distinguished. The aptasensor also exhibited satisfactory selectivity, stability and reproducibility. Moreover, when proposed method and ELISA-kit were simultaneously applied to artificial cerebrospinal fluid (A-CSF) samples, the obtained results were completely consistent, reflecting the potential clinical application value of this work. [Display omitted] • The AgCNS was prepared by an extremely simple and environmental one-pot method. • AgCNS was an innovative luminophore with excellent ECL performance. • It is a new attempt of g-C 3 N 4 based MOGs in the field of ECL sensor. • THS was firstly used in the fabrication of ECL aptasensor for AβOs analysis. • The synergistic strategy offers a new opportunity for clinical application. [ABSTRACT FROM AUTHOR]

Cathodic corrosion is an electrochemical process that induces restructuring, roughening, and etching of metal surfaces at a highly negative surface charge density, yet, details of the reaction mechanism are not fully resolved. An in‐depth fundamental understanding of the processes and parameters underlying cathodic corrosion is crucial for tailoring the surface structure of the metal electrodes and for synthesizing shape‐ and size‐controlled nanoparticles. Here, we investigate the relevance of water and hydrogen evolution in the cathodic corrosion process. To achieve this aim, Au electrodes were polarized at ‐1.6 V versus RHE in KOH and NaOH electrolytes prepared using different water + methanol mixtures. Structural changes of the Au surfaces were studied by cyclic voltammetry and monitored by scanning electron microscopy (SEM). Most importantly, cathodic corrosion does not take place in the absence of water. There is no detectable bubble formation due to the hydrogen evolution reaction on Au in purely methanolic alkali. Furthermore, the electrochemically active surface area, facet distribution, and surface morphology of Au electrodes are significantly altered upon cathodic polarization as a function of the water concentration. Cathodic corrosion features become more and more pronounced with a further increase in water content. In addition, substantial differences in the surface structure of Au are observed as a function of the nature and concentration of alkali metal cations. Overall, this study provides a more detailed understanding of the role of water and the hydrogen evolution reaction in dominating cathodic corrosion, which might advance the understanding of this phenomenon. [ABSTRACT FROM AUTHOR]

Single junction solar cells with organic-inorganic perovskites have achieved efficiency > 25%, yet they suffer from long-term durability and toxicity. Additionally, all the best-performing perovskite light harvesters contain lead, hindering their real-time application. Herein, we report preliminary studies with the SCPAS-1D software package on three different perovskite light harvesters, namely FAPbI3, FASnI3, and CsSnI3, considering an approach towards stable and environmentally benign perovskite light harvesters. Additionally, to extract the best performance, each perovskite light harvester is analysed with four electron transport layers, namely TiO2, SnO2, BaSnO3, and La doped BaSnO3. The physical parameters such as thickness, doping, and defect density are optimised for the subsequent films to deliver high performance. Further, the operating temperature-dependent variation in power conversion efficiency and other solar cell parameters are also analysed. In an attempt to replace the high-cost gold counter electrode, a comparative study on the performance of other possible counter electrodes is also comprehensively detailed. [ABSTRACT FROM AUTHOR]

Epirubicin is prescribed as an essential drug for treating breast, prostate, uterine, and gastrointestinal cancers. It has many side effects, such as heart failure, mouth inflammation, abdominal pain, fever, and shortness of breath. Its measurement is necessary by straightforward and cheap methods. The application of aptamer-based electrochemical sensors is accounted as a selective option for measuring different compounds. In this work, a thiol-modified aptamer was self-assembled on the surface of the gold electrode (AuE) boosted with carbon nano-onions (CNOs), and coupled with methylene blue (MB) as an electroactive tracker to achieve a sensitive and selective aptasensor. In the absence of the epirubicin, CNOs binds to the aptamer through a π-π interaction enhancing the MB electrochemical signal. When epirubicin binds to the aptamer, the adsorption of CNOs and MB to the aptamer is not well established, so the electrochemical signal is reduced, consequently, the epirubicin value can be measured. The prepared aptasensor demonstrated an excellent sensitivity with a curve slope of 0.36 μI/nM, and 3 nM limit of detection in the linear concentration range of 1–75 nM. The prepared aptasensor was accurately capable of measuring epirubicin in blood serum samples. [ABSTRACT FROM AUTHOR]

Surface cleaning of the working electrode has a key role in improved electrochemical and physicochemical properties of the biosensors. Herein, chemical oxidation in piranha, chemical cleaning in potassium hydroxide-hydrogen peroxide, combined (electro-) chemical alkaline treatment, and potential cycling in sulfuric acid were applied to gold finish electrode surfaces deposited onto three different substrates; low temperature co-fired ceramics (LTCC), polyethylene naphthalate (PEN), and polyimide (PI), using three different deposition technologies; screen printing, inkjet printing, and electroplating (printed circuit board technology, PCB) accordingly. The effects of the (electro-) chemical treatments on the gold content and electrochemical responses of LTCC, PEN, and PCB applicable for aptamer-based sensors are discussed. In order to assess the gold surface and to compare the efficiency of the respective cleaning procedures; cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed. LTCC sensors electrochemically cycled in sulfuric acid resulted in the most gold content on the electrode surface, the lowest peak potential difference, and the highest charge transfer ability. While, for PEN, the highest elemental gold and the lowest peak-to-peak separation were achieved by a combined (electro-) chemical alkaline treatment. Gold content and electrochemical characteristics on the PCB surface with extremely thin gold layer could be slightly optimized with the chemical cleaning in KOH + H2O2. The proposed cleaning procedures might be generally applied to various kinds of Au electrodes fabricated with the same conditions comparable with those are introduced in this study. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylenedioxythiophene) (PEDOT) and its derivatives have demonstrated potential in the development of bioelectrodes because of their superior conductivity. However, developing reliable implanted bioelectrodes requires improvements in biocompatibility and the prevention of nonspecific adhesion. In this study, a six ethylene glycol (EG)‐functionalized EDOTs with three different EG lengths (tri‐EG, tetra‐EG, and hexa‐EG) and two types of end groups, hydroxyl (−OH) and methoxy (−OCH3) is synthesized and systematically investigated. By coating them on gold electrodes using electropolymerization, the surface and electrochemical properties of these functionalized PEDOT‐coated electrodes are investigated. Although PEDOT with −OH groups on the surface is more hydrophilic, those with −OCH3 groups on the surface exhibit higher electrochemical activity and lower impedance. The increase in EG units and −OCH3 groups on the surface effectively reduces the adhesion between the PEDOT and atomic force microscopy tips. PEDOT with longer EG lengths and −OCH3 groups exhibits relatively few adhered platelets, and the results of the analysis of hydrated states through differential scanning calorimetry are consistent with those of the platelet adhesion test. This study suggests that a tetra(EG)‐functionalized PEDOT with −OCH3 groups on the surface is a promising coating for implanted bioelectrode applications. [ABSTRACT FROM AUTHOR]

Controlling food safety and preventing the growing spread of antibiotics into food products have been challenging problems for the protection of human health. Hence, the development of easy-to-use, fast, and sensitive analytical methods for the detection of antibiotics in food products has become one of the priorities in the food industry. In this paper, an electrochemical platform based on the ssDNA aptamer for the selective detection of tetracycline has been proposed. The aptasensor is based on a thiolated aptamer, labelled with ferrocene, which has been covalently co-immobilized onto a gold electrode surface with 6-mercaptohexan-1-ol. The changes in the redox activity of ferrocene observed on the aptamer–antibiotics interactions have been the basis of analytical signal generation registered by square-wave voltammetry. Furthermore, the detection of tetracycline-spiked cow milk samples has been successfully demonstrated. The limits of detection (LODs) have been obtained of 0.16 nM and 0.20 nM in the buffer and spiked cow milk, respectively, which exceed the maximum residue level (225 nM) more than 1000 times. The proposed aptasensor offers high selectivity for tetracycline against other structurally related tetracycline derivatives. The developed biosensor characterized by simplicity, a low detection limit, and high reliability shows practical potential for the detection of tetracycline in animal-origin milk. [ABSTRACT FROM AUTHOR]

In this work, a novel ratiometric electrochemical readout platform was proposed and developed for the fast and flexible analysis of M.SssI methyltransferase (MTase) activity. In this platform, two hairpin DNAs (H1 and H2) were designed. H1 contains the palindromic sequence of 5′-CCGG-3′ in its stem which could be methylated and hybridize with H2 labeled by methylene blue (MB) as one of the signal reporters on a gold electrode (GE) in the presence of M.SssI MTase. Additionally, a specific immunoreaction was introduced by conjugating an anti-5-methylcytosine antibody, a DNA CpG methylation recognition unit, with 1,3-ferrocenedicarboxylic acid (Fc) as the second signal reporter. The results showed that when the Fc tag approaches, the MB tag was far from the gold electrode surface, resulting in a decrease in the oxidation peak current of MB (IMB) and an increase in the oxidation peak current of Fc (IFc). The ratiometric electrochemical method above shows the linear range of detection was 0 U/mL 40 U/mL with a detection limit of 0.083 U/mL (the mean signal of blank measures þ3s). [ABSTRACT FROM AUTHOR]

The feasibility of designing a highly selective and sensitive label‐free cost‐effective biosensor to determine Hg2+ ions using gold electrodes functionalized with short‐chain, thymine‐rich, ss‐DNA oligonucleotides wrapped MWNTs is examined. The potassium ferricyanide was used as a redox marker for analytical signal generation. Biosensor response was based on the difference in the electrochemical signal before and after subjecting it to a sample containing Hg2+ ions. The lowest detection limit of 1 femtomolar (fM) of mercury ions was observed in the aqueous medium, together with good selectivity against common metal cations. The method developed was successfully applied for the determination of Hg2+ ions in environmental waste water samples. [ABSTRACT FROM AUTHOR]

A highly sensitive kanamycin electrochemiluminescence (ECL) switch sensor was constructed. A signal element consisting of ordered mesoporous carbon loaded with indium oxide nanoparticles/carbon quantum dots (OMC/In2O3/C-dots) was assembled on the surface of a gold electrode. Then, a molecularly imprinted polymer (MIP) was prepared on the modified electrode surface using kanamycin as the template molecule and o-aminophenol as the functional monomer. After kanamycin elution, the prepared sensor retained specific kanamycin recognition sites. OMC/In2O3 effectively amplified the ECL signal of the C-dots, thereby enhancing the detection sensitivity, whereas kanamycin quenched the signal. Therefore, the imprinted sites acted as a switch, providing a new method for detecting kanamycin. Under the optimal experimental conditions, the concentration of kanamycin was proportional to the degree of ECL quenching within a linear range of 5–4500 × 10−12 mol L−1 at 0.8 V (vs. Ag/AgCl electrode electrode), and the detection limit was 5.8 × 10−13 mol L−1. When applied to the detection of kanamycin in actual samples, such as chicken, duck, pork, and milk, the recovery for spiked samples was in the range 92.7–110%. [ABSTRACT FROM AUTHOR]

In this study we demonstrate a high-performance polarization rotator (PR) based on flat-shaped photonic crystal fiber. The flat surfaces of the fiber are plated on gold films as electrodes, and the core of the structure is filled with liquid crystal. The polarization rotation characteristics of the flat-shaped fiber can be effectively adjusted by applying external voltage. The optical properties are analyzed using the finite element method (FEM). The results show that the magnitude of the modulation voltage is closely related to the thickness of the flat fiber. When the fiber thickness is 20 μm, only 100 V is required to achieve the highest PR performance. In the wavelength of the 1.55 μm band (~200 nm bandwidth), the conversion length of the PR is only 3.99 μm, the conversion efficiency is close to 100%, and the minimum crosstalk value is −26.2 dB. The presented PR, with its excellent performance, might enable promising applications in the communication system and the photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA) is widely used in the manufacture of polycarbonate and epoxy-resin-based products, and BPA contamination often happens in a variety of types of environment and food stuffs. BPA can cause many harmful effects to health due to its high toxicity. The rapid detection of BPA is of great significance in environmental monitoring and food safety. Nucleic acid aptamers show advantages in biosensors due to good chemical stability, the ease of labeling functional groups, and target binding that induces conformation change. Here, we performed a thorough characterization of the binding performance of one 60-nt anti-BPA DNA aptamer with isothermal titration calorimetry (ITC). We found the crucial region of the aptamer sequence for affinity binding with BPA, and the aptamer was able to be truncated to 29-nt DNA without losing affinity. We then developed a simple reagent-less electrochemical aptamer-based sensor for rapid BPA detection with this engineered aptamer. The truncated aptamer with a redox tag methylene blue (MB) was immobilized on a gold electrode. BPA-binding induced the conformation change of the MB-labeled aptamer, moving the MB close to the electrode surface and causing a significant current increase in MB in square wave voltammetry (SWV). Under optimized conditions, we achieved the quantitative detection of BPA with a detection limit of BPA at 0.1 μM. This sensor showed quick response to BPA and could be regenerated by washing with deionized water. This sensor was selective, and it allowed detecting BPA in complex samples, showing its potential in practice. This study will help in further applications of the aptamers of BPA. [ABSTRACT FROM AUTHOR]

The limit of detection (LOD) is defined as the lowest quantity or concentration of a component that can be reliably distinguished from the limit of blank (LOB). LOD value is one of the most important parameters considered for many determination methods and is usually calculated on the linear correlation between signal and concentration. However, the linear correlation may not always be obtained in experimental studies. We claim that data with low linear correlation have meaning, and we present such a study because analytical studies based on these data are not easily understood in the literature. In this manuscript, we suggest that a calibration curve can be obtained from nonlinear data points and the LOD value can be calculated. We tested this approach for the determination of exosomes and supported it with mathematical calculations. We produced a label-free sensor using anti-CD63 on the gold electrode for selective and reliable impedimetric detection of the exosomes obtained from Colo 320 cell lines in data points that are high concentrations and out of linearity. We characterized in detail what each calculation means. This sensor with a LOD value of 3.90×1011 exosome particles µL-1 and with a cubic polynomial model for the calibration curve was considered sensitive and reliable, especially for high vesicle content of samples such as cell culture medium. [ABSTRACT FROM AUTHOR]

An electrochemical sensor was fabricated for the rapid and simple detection of enrofloxacin (EF). Modification of screen-printed gold electrodes (SPE) with molecularly imprinted polymers (MIPs) allowed the detection of enrofloxacin by square wave voltammetry (SWV), measuring the oxidation peak at +0.9 V. The detection principle of molecularly imprinted polymers (MIPs) is based on the formation of binding sites with affinities and specificities comparable with those of natural antibodies. The detection of enrofloxacin showed a linear range of 0.01–0.1 mM with a detection limit LOD of 0.02 mM. The development of a non-imprinted polymer (NIP) control sensor allowed for better and more efficient detection. In addition, the sensor is portable, having the advantage of analyzing and detecting molecules of interest without the need to take the sample to a laboratory. [ABSTRACT FROM AUTHOR]

Cyanobacterial extracellular polymeric substances "EPS" have attracted intensive concern in biomedicine and food. Nevertheless, the use of those polymers as a sensor coating material has not yet been investigated mainly for microplastic detection. This study focuses on the application of EPS as a sensitive membrane deposited on a gold electrode and investigated with electrochemical impedance spectroscopy to detect four types of microplastics with a size range of 0.1 µm to 1 mm. The surface properties of this impedimetric sensor were investigated by Scanning electron microscopy, Fourier transforms infrared spectroscopy, and X-ray spectroscopy and, showed a high homogenous structure with the presence of several functional groups. The measurements showed a high homogenous structure with the presence of several functional groups. The EPS-based sensor could detect the four tested microplastics with a low limit of detection of 10–11 M. It is the first report focusing on EPS extracted from cyanobacteria that could be a new quantification method for low concentrations of microplastics. [ABSTRACT FROM AUTHOR]

Coronavirus 2019 (COVID-19) spreads an extremely infectious disease where there is no specific treatment. COVID-19 virus had a rapid and unexpected spread rate which resulted in critical difficulties for public health and unprecedented daily life disruption. Thus, accurate, rapid, and early diagnosis of COVID-19 virus is critical to maintain public health safety. A graphite oxide-based field-effect transistor (GO-FET) was fabricated and functionalized with COVID-19 antibody for the purpose of real-time detection of COVID-19 spike protein antigen. Thermal evaporation process was used to deposit the gold electrodes on the surface of the sensor substrate. Graphite oxide channel was placed between the gold electrodes. Bimetallic nanoparticles of platinum and palladium were generated via an ultra-high vacuum (UHV) compatible system by sputtering and inert-gas condensation technique. The biosensor graphite oxide channel was immobilized with specific antibodies against the COVID-19 spike protein to achieve selectivity and specificity. This technique uses the attractive semiconductor characteristics of the graphite oxide-based materials resulting in highly specific and sensitive detection of COVID-19 spike protein. The GO-FET biosensor was decorated with bimetallic nanoparticles of platinum and palladium to investigate the improvement in the sensor sensitivity. The in-house developed biosensor limit of detection (LOD) is 1 fg/mL of COVID-19 spike antigen in phosphate-buffered saline (PBS). Moreover, magnetic labelled SARS-CoV-2 spike antibody were studied to investigate any enhancement in the sensor performance. The results indicate the successful fabrication of a promising field effect transistor biosensor for COVID-19 diagnosis. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are attracting widespread attention due to their exceptional photovoltaic performance and their potential for large‐scale production via low‐cost, high‐throughput roll‐to‐roll (R2R) methods. Full realization of this production approach requires replacement of the evaporated metal electrode commonly used in PSCs. Here, a novel vacuum‐free R2R‐compatible method is introduced to fabricate and deposit printed electrodes based on electrically conductive pastes, which avoids potential loss of PSC performance due to solvent migration from the pastes. Flexible R2R‐fabricated PSCs with record power conversion efficiencies (PCEs) of up to 16.7% are produced by vacuum‐free deposition of all functional layers, apart from the transparent conductive electrode. This performance compares very favorably with that of control flexible PSCs comprising an evaporated gold electrode, which displays PCEs of up to 17.4%. Furthermore, the PSCs comprising a printed electrode demonstrate outstanding operational and mechanical stability, with negligible loss of PCE after 24 h of continuous 1‐sun illumination and retention of more than 90% of their initial PCE after 3000 cyclic bends. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are small non-coding RNAs with ~ 22 nucleotides, playing important roles in the post-transcriptional regulation of gene expression. The expression profiles of many miRNAs are closely related to the occurrence and progression of cancer and can be used as biomarkers for cancer diagnosis and prognosis. However, their intrinsic properties, such as short length, low abundance and high sequence homology, represent great challenges in miRNA detection of clinical samples. To overcome these challenges, we developed a simple, ultrasensitive detection platform of electrochemical miRNAs chip (e-miRchip) with a novel signal amplification strategy using silver nanoparticle reporters (AgNRs) for multiplexed, direct, electronic profiling of miRNAs. A two-step hybridization strategy was used to detect miRNAs, where the target miRNA hybridizes with a stem-loop probe to unlock the probe first, and the opened stem-loop can further hybridize with AgNRs for signaling amplification. To enhance the detection sensitivity, the gold nanoflower electrodes (GNEs) were constructed in the microaperture arrays of the e-miRchips by electroplating. With the optimal size of the GNEs, the e-miRchip showed excellent performance for miR-21 detection with a detection limit of 0.56 fM and a linear range extended from 1 fM to 10 pM. The e-miRchip also exhibited good specificity in differentiating the 3-base mismatched sequences of the target miRNA. In addition, the e-miRchip was able to directly detect miR-21 expression in the total RNA extracts or cell lysates collected from lung cancer cells and normal cells. This work demonstrated the developed e-miRchip as an efficient and promising miniaturized point-of-care diagnostic device for the early diagnosis and prognosis of cancers. [ABSTRACT FROM AUTHOR]

This article describes three novel electrochemical biosensing platforms developed to determine the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike antigen protein: glutaraldehyde, SARS-CoV-2 spike antibody and bovine serum albumin; N,N-dicyclohexyl carbodiimide/4-(dimethylamino)pyridine functionalised SARS-CoV-2 spike antibody and bovine serum albumin; and 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride/N-hydroxysuccinimide functionalised SARS-CoV-2 spike antibody and bovine serum albumin modified cysteine-based gold-flower modified glassy carbon electrodes. Two of the produced biosensors having better signals were used to determine the SARS-CoV-2 spike antigen in spiked-saliva and clinical samples containing gargle and mouthwash liquids and characterised using cyclic voltammetry, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The study provides highly significant information in terms of how coupling reagents ought to be used with linkers consisting of both amine and carboxylic acid terminals (i.e. cysteine). The electrochemical cathodic signals based on antibody–antigen protein interactions at approximately −270 mV were evaluated as a response using square wave voltammetry, and they increased in proportion to the SARS-CoV-2 spike antigen. The limit of detection values were 0.93 and 46.3 ag mL−1 in a linear range from 1 ag mL−1 to 100 pg mL−1 and from 100 ag mL−1 to 10 ng mL−1 and the recovery and relative standard deviation values for spiked-saliva samples were 99.50% and 99.40%, and 3.87% and 0.13% for BSA/S-AB/GluAl/Cys/Au/GCE and BSA/S-AB/f-Cys/Au/GCE, respectively. The results showed that both biosensing platforms could be selectively and accurately used to diagnose COVID-19 in RT-PCR-approved clinical samples. [ABSTRACT FROM AUTHOR]

Highly active, robust, cheap, and environmentally benign electrocatalysts for the oxygen evolution reaction (OER) are critically important to develop a sustainable artificial energy cycle. Here, we report the in situ synthesis of mononuclear manganese(III) pincer complexes [Mn(OAc)(L)(cbpy)] (1) and [Mn(OAc)(L1)(cbpy)] (2) on a gold electrode surface through a self-assembly process (where OAc = acetate, cbpy = 2,2′-bipyridine-4-carboxylic acid anion, L = N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate (2-) and L1 = N,N′-(diphenyl)-2,6-pyridinedicarboxamidate (2-)) and explore their activity for the electrocatalytic OER (2H2O = 4H+ + 4e− + O2) in neutral pH medium. The modified electrode was characterized by using microscopic (FE-SEM), spectroscopic (EDX, ATR-FTIR, SERS), and electrochemical (CV and EIS) methods. The newly developed heterogenized molecular catalysts 1 and 2 can catalyze the OER exceptionally well with a low overpotential of 260 mV at J = 3.2 mA cm−2 and 275 mV at J = 2.46 mA cm−2, respectively. The Tafel slopes were found to be 68 and 77 mV decade−1 for the catalysts 1 and 2, respectively. These results support the higher OER activity of complex 1 than complex 2 under similar conditions and this may be due to more electron donating power of pincer ligand L than L1, which in turn stabilizes the high valent manganese complex intermediates. Furthermore, after long-term controlled potential electrolysis (∼ 6 h), the surface-immobilized manganese complex does not decompose into manganese oxide and preserves the molecular identity as evident from electrochemical, spectroscopic and microscopic results. [ABSTRACT FROM AUTHOR]

In the scientific literature, it has been documented that electrochemical genosensors are novel analytical tools with proven clinical diagnostic potential for the identification of carcinogenic processes due to genetic and epigenetic alterations, as well as infectious diseases due to viruses or bacteria. In the present work, we describe the construction of an electrochemical genosensor for the identification of the k12p.1 mutation; it was based on use of Screen-Printed Gold Electrode (SPGE), Cyclic Voltammetry (CV), and Atomic Force Microscopy (AFM), for the monitoring the electron transfer trough the functionalized nanostructured surface and corresponding morphological changes. The sensitivity of the genosensor showed a linear response for the identification of the k12p.1 mutation of the K-ras gene in the concentration range of 10 fM to 1 μM with a detection limit of 7.96 fM in the presence of doxorubicin (Dox) as DNA intercalating agent and indicator of the hybridization reaction. Thus, the electrochemical genosensor developed could be useful for the identification of diseases related with the K-ras oncogene. [ABSTRACT FROM AUTHOR]