Effects of sonochemical approach and induced contraction of core-shell bismuth sulfide/graphitic carbon nitride as an efficient electrode materials for electrocatalytic detection of antibiotic drug in foodstuffs.

Ultrasonic-enhanced surface-active bismuth trisulfide based core-shell nanomaterials were developed and used as an efficient modified electrode material to construct a highly sensitive antibiotic sensor. The core-shell Bi2S3@GCN electrode material was directly synthesized by in-situ growth of GCN on Bi2S3 to form core-shell like nanostar (Ti-horn, 30 kHz, and 70 W/cm2). The electrocatalyst of Bi2S3@GCN nanocomposites was efficaciously broadened towards electrochemical applications. As synthesized Bi2S3@GCN promoted the catalytic ability and electrons of GCN to transfer to Bi2S3. The single-crystalline GCN layers were uniformly grown on the surface of the Bi2S3 nanostars. Under the optimal conditions of electrochemical analysis, the CPL sensor exhibited responses directly proportional to concentrations (toxic chemical) over a range of 0.02-374.4 µM, with a nanomolar detection limit of 1.2 nM (signal-to-noise ratio S/N = 3). In addition, the modified sensor has exhibited outstanding selectivity under high concentrations of interfering chemicals and biomolecules. The satisfactory CPL recoveries in milk product illustrated the credible real-time application of the proposed Bi2S3@GCN sensors for real samples, indicating promising potential in food safety department and control. Additionally, the proposed electrochemical antibiotic sensor exhibited outstanding performance of anti-interfering ability, high stability and reproducibility.

Ruthenium oxide nanoparticles immobilized over Citrus limetta waste derived carbon material for electrochemical detection of hexestrol.

Hexestrol is a non-steroidal estrogen which causes carcinogenic effects in animals. It is therefore important to develop sensitive and selective test methods for its early detection. Herein, we report the development of an electrochemical sensor to detect hexestrol in ultralow concentrations. In order to devise a simple and cost-effective hexestrol sensing electrode, attention is paid to the development of biomass-derived porous carbon (PCB) with large surface area and suitable porosity to immobilize ruthenium oxide nanoparticles (RuO2 NPs, 3-4 nm). The leftover Citrus limetta pulp is chosen as waste biomass since it has N and O based chemical species. Structural, morphological and compositional analysis of PCB and RuO2@PCB revealed well-dispersed RuO2 NPs over the PCB surface. High loading (5.27 at%) of Ru content is achieved due to the large surface area of PCB. Cyclic voltammetry, chronoamperometry and differential pulse voltammetry results suggest that the RuO2@PCB/ITO electrode is capable of detecting hexestrol concentration (in the range of 1 × 10-7-2 × 10-5 M). The practical application of hexestrol detection in milk samples demonstrates the recovery from 96.28 to 101%.

Disposable multiplexed electrochemical sensors based on electro-triggered selective immobilization of probes for simultaneous detection of DNA and proteins.

Electrically addressable covalent immobilization of probes on a multiplexed electrode for the simultaneous detection of multiple targets within the same sample is often regarded as a difficult milestone to be achieved. Herein, we demonstrated a reagentless disposable multiplexed electrochemical DNA and aptamer-based sensing platform for the simultaneous determination of various targets. The electrochemically triggered "click" chemistry was developed, and three biomarkers, including p53, thrombin, and VEGF165 were used as model analytes. The proposed sensor consisted of three independent screen-printed carbon electrodes (SPCE), with an alkyne-azide cycloaddition reaction that was activated selectively by means of electrical triggering, so that different DNA probes can be modified on the desired electrode units in sequence. In terms of simultaneous detection, the sensor was able to quantify the DNA target of p53 with a detection limit of 0.35 nM, whereas the limits of detection for protein quantification of thrombin and VEGF165 were 0.22 nM and 0.014 nM, respectively. The proposed sensor not only showed encouraging reproducibility and stability, but also performed well even in 50% serum samples. Therefore, the work described here offers a general strategy for developing a multiplexed sensor with promising potential to achieve rapid, simple and cost-effective analysis of biological samples.

Combination of Efficiency with Easiness, Speed, and Cheapness in Development of Sensitive Electrochemical Sensors.

Nowadays, electrochemical techniques can be considered as a suitable alternative technique besides UV/Vis spectroscopy, liquid chromatography, capillary electrophoresis, mass spectroscopy, NMR for evaluation and determination of different electroactive compounds. Solid electrodes such as carbon and metal-based substrates are common for electrochemical applications. Especially, during two past decades, different types of modified electrodes with these solid electrodes have been developed for fast, sensitive, and selective analysis of various important analyses (biomolecules, enzymes, and drugs) in a wide range of real samples. These applications are highly efficient, cost effective and facile fabrication procedures of the electrode modification can be employed. In the present review, at first, some recently developed high performance bare and modified electrodes are evaluated based on their outstanding properties. In the next step, developed new procedures or fabricated modified electrodes with good sensitivity based on simple and cheap protocols are introduced and discussed.

Commercial Screen-Printed Electrodes Based on Carbon Nanomaterials for a Fast and Cost-Effective Voltammetric Determination of Paracetamol, Ibuprofen and Caffeine in Water Samples.

Carbon screen-printed electrode (SPCE), multi-walled carbon nanotubes modified screen-printed electrode (SPCNTE), carbon nanofibers modified screen-printed electrode (SPCNFE), and graphene modified screen-printed electrode (SPGPHE) were in a pioneer way tested as sensors for the simultaneous determination of the two most consumed pain-killers, paracetamol (PA) and ibuprofen (IB), and the stimulant caffeine (CF) in water by differential pulse voltammetry (DPV). Their analytical performances were compared, and the resulting sensitivities (2.50, 0.074, and 0.24 µA V mg-1 L for PA, IB, and CF, respectively), detection limits (0.03, 0.6, and 0.05 mg L-1 for PA, IB, and CF, respectively) and quantification limits (0.09, 2.2, and 0.2 mg L-1 for PA, IB, and CF, respectively) suggested that the SPCNFE was the most suitable carbon-based electrode for the voltammetric determination of the selected analytes in water at trace levels. The methodology was validated using both spiked tap water and hospital wastewater samples. The results were compared to those achieved by liquid chromatography-tandem mass spectrometry (LC-MS/MS), the technique of choice for the determination of the target analytes.

Facile Preparation of Fe3O4/C Nanocomposite and Its Application for Cost-Effective and Sensitive Detection of Tryptophan.

In this study, we reported facile synthesis of Fe3O4/C composite and its application for the cost-effective and sensitive determination of tryptophan (Trp) in human serum samples. Fe3O4/C composites were prepared by a simple one-pot hydrothermal method followed by a mild calcination procedure, using FeCl3∙6H2O as Fe3O4 precursor, and glucose as reducing agent and carbon source simultaneously. The Fe3O4/C composite modified glassy carbon electrode (Fe3O4/C/GCE) was prepared by drop-casting method. The microstructure and morphology of Fe3O4/C composite was characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Due to large specific surface area and synergistic effect from Fe3O4 nanoparticles and carbon coating, Fe3O4/C composite showed excellent electrocatalytic activity toward the oxidation of Trp. As a result, the proposed Fe3O4/C/GCE displayed superior analytical performances toward Trp determination, with two wide detection ranges (1.0-80 µM and 80-800 µM) and a low detection limit (0.26 µM, S/N = 3). Moreover, successful detection of Trp in human serum samples further validate the practicability of the proposed sensor.

Low cost non-electromechanical technique for the purification of giant unilamellar vesicles.

Lipid membranes of giant unilamellar vesicles (GUVs) with diameters greater than 10 µm are promising model membranes for investigating the physical and biological properties of the biomembranes of cells. These are extensively used for the study of the interaction of various membrane-active agents, where purified and similar-size oil-free GUVs are necessary. Although the existing membrane filtering method provides the required quality and quantity of GUVs, it includes a relatively expensive double-headed peristaltic pump. In our proposed non-electromechanical technique, gravity is used to maintain the flow of buffer, wherein the flow rate of buffer with the suspension of GUVs is controlled by a locally available low cost roller clamp regulator. We have characterized the results of this non-electromechanical approach in terms of size distribution, average size, flow rate and efficiency for dioleoylphosphatidylglycerol (DOPG)/dioleoylphosphatidylcholine (DOPC)-GUVs prepared by the natural swelling method. The technique purifies the GUVs by removing the non-entrapped solutes at an optimum flow rate 1.0-2.0 mL/min. In addition, it gives similar results to the pump-driven membrane filtering method. Therefore, it might be a cost effective technique for the purification of GUVs without employing any electromechanical devices.

Metal-organic framework derived carbon-based sensor for monitoring of the oxidative stress of living cell and assessment of antioxidant activity of food extracts.

A novel non-enzymatic superoxide anion radical (O2•-) sensor was prepared by silver nanoparticles (AgNPs) decorated organic frameworks (MOFs) compound-derived metal oxide coated carbon material. Transmission electron microscopy (TEM) was employed to characterize morphologies and structures of the as-prepared samples AgNPs/Co3O4@C. Electrochemical studies indicated that the AgNPs/Co3O4@C/GCE exhibited excellent detection ability to O2•-. It offered a linear range of 8 orders of magnitude and a super low detection limits of 0.0564 pM. The sensor was successfully adapted to detection of O2•- released from living cells. Furthermore, the capacities of scavenging O2•- of food antioxidants were also studied by electrochemical method at cellular milieu. Accordingly, this work provided tremendous potential for reduction incidence of oxidative stress by intaking food antioxidants.

Trypsin electrochemical sensing using two-dimensional molecularly imprinted polymers on 96-well microplates.

Molecular imprinting is an efficient technology to create artificial receptors with antibody-like binding properties for a variety of applications such as separation and sensing. In this work, a new sensing method was introduced by combining a two-dimensional molecularly imprinted polymer (2D-MIP) film with copper oxide nanoparticles (CuO NPs) labeling for signal conversion and amplification. CuO labeling can effectively monitor the thickness of 2D-MIPs to achieve the best imprinting effect. Trypsin imprinted polymer based electrochemical sensor on 96-well microplates was constructed and a good dynamic response was observed in the range of 0.5-500 ng/mL. Furthermore, detections of trypsin in fetal bovine serum were demonstrated using the imprinted polymer thin films. Our electrochemical sensors possess an excellent specificity, fast kinetics, high sensitivity and low cost, which have great potential in biological analysis.

Rapid voltammetric method for quinine determination in soft drinks.

A novel voltammetric assay for quinine (QN) determination using an electrochemically pretreated pencil graphite electrode is described. The detection limit of QN was 2 × 10-7 M. The method possesses some obvious advantages including extreme simplicity, rapid response, and low cost.

Amperometric Gas Sensors as a Low Cost Emerging Technology Platform for Air Quality Monitoring Applications: A Review.

This review examines the use of amperometric electrochemical gas sensors for monitoring inorganic gases that affect urban air quality. First, we consider amperometric gas sensor technology including its development toward specifically designed air quality sensors. We then review recent academic and research organizations' studies where this technology has been trialed for air quality monitoring applications: early studies showed the potential of electrochemical gas sensors when colocated with reference Air Quality Monitoring (AQM) stations. Spatially dense networks with fast temporal resolution provide information not available from sparse AQMs with longer recording intervals. We review how this technology is being offered as commercial urban air quality networks and consider the remaining challenges. Sensors must be sensitive, selective, and stable; air quality monitors/nodes must be electronically and mechanically well designed. Data correction is required and models with differing levels of sophistication are being designed. Data analysis and validation is possibly the biggest remaining hurdle needed to deliver reliable concentration readings. Finally, this review also considers the roles of companies, urban infrastructure requirements, and public research in the development of this technology.

Validated electrochemical and chromatographic quantifications of some antibiotic residues in pharmaceutical industrial waste water.

Realistic implementation of ion selective electrodes (ISEs) into environmental monitoring programs has always been a challenging task. This could be largely attributed to difficulties in validation of ISE assay results. In this study, the electrochemical response of amoxicillin trihydrate (AMX), ciprofloxacin hydrochloride (CPLX), trimethoprim (TMP), and norfloxacin (NFLX) was studied by the fabrication of sensitive membrane electrodes belonging to two types of ISEs, which are polyvinyl chloride (PVC) membrane electrodes and glassy carbon (GC) electrodes. Linear response for the membrane electrodes was in the concentration range of 10-5-10-2 mol/L. For the PVC membrane electrodes, Nernstian slopes of 55.1, 56.5, 56.5, and 54.0 mV/decade were achieved over a pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. On the other hand, for GC electrodes, Nernstian slopes of 59.1, 58.2, 57.0, and 58.2 mV/decade were achieved over pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. In addition to assay validation to international industry standards, the fabricated electrodes were also cross-validated relative to conventional separation techniques; high performance liquid chromatography (HPLC), and thin layer chromatography (TLC)-densitometry. The HPLC assay was applied in concentration range of 0.5-10.0 µg/mL, for all target analytes. The TLC-densitometry was adopted over a concentration range of 0.3-1.0 µg/band, for AMX, and 0.1-0.9 µg/band, for CPLX, NFLX, and TMP. The proposed techniques were successfully applied for quantification of the selected drugs either in pure form or waste water samples obtained from pharmaceutical plants. The actual waste water samples were subjected to solid phase extraction (SPE) for pretreatment prior to the application of chromatographic techniques (HPLC and TLC-densitometry). On the other hand, the fabricated electrodes were successfully applied for quantification of the antibiotic residues in actual waste water samples without any pretreatment. This finding assures the suitability of the fabricated ISEs for environmental analysis.

Anaerobes in Bioelectrochemical Systems.

In bioelectrochemical systems (BES), the catalytic activity of anaerobic microorganisms generates electrons at the anode which can be used, for example, for the production of electricity or chemical compounds. BES can be used for various purposes, including wastewater treatment, production of electricity, fuels and chemicals, biosensors, bioremediation, and desalination. Electrochemically active microorganisms are widely present in the environment and they can be found, in sediment, soil, compost, wastewaters and their treatment plants. Exoelectrogens are microorganisms capable of donating electrons to anode electrode or accepting electrons from cathode electrode and are mainly responsible for current generation or use in BES. However, current generation from fermentable substrates often requires the presence of electrochemically inactive microorganisms that break down complex substrates into metabolites which can be further utilized by exoelectrogens. The growth and electron transfer efficiency of anaerobes depend on several parameters, such as system architecture, electrode material and porosity, electrode potential and external resistance, pH, temperature, substrate concentration, organic loading rate, and ionic strength. In this chapter, the principles and microbiology of bioelectrochemical systems as well as selective factors for exoelectrogens are reviewed. The anaerobic microorganisms and their electron transfer mechanisms at the anode and cathode are described and future aspects are briefly discussed.

Electrochemical Preparation and Characterization of a Gold Nanoparticles Graphite Electrode: Application to Myricetin Antioxidant Analysis.

Graphite material is abundantly available from recyclable sources. It possesses a good electrical conductance property, which makes it an attractive material as a working electrode. However, due to a high activation overpotential it has limited applications as compared to other solid metal electrodes. In this present work, we obtained a graphite rod from a used battery, and carried out electrochemical improvements by electro-deposition with gold nanoparticles (AuNPs). The heterogeneous electron transfer rate and electron transfer resistance of the fabricated electrode were improved. The electrode overpotential has shown improvement by 50 mV, and the effective surface area has increased by 2 fold. To determine the practicability of the AuNPs/graphite electrode, we used the electrode in the analysis of myricetin. A square-wave voltammetry was used in the analysis, and the detection response increased by 2.5 fold, which suggested an improvement in the electrode sensitivity.

Electrochemical monitoring of the interaction between Temozolamide and nucleic acids by using disposable pencil graphite electrodes.

Temozolomide (TMZ) is an anticancer drug used for the treatment of adult brain tumour and skin cancer. The biomolecular interaction between TMZ and DNA was investigated for the first time in this study using disposable pencil graphite electrodes (PGEs) in combination with electrochemical techniques. The surface confined interactions between TMZ and different type of nucleic acids were performed. Before/after surface confined interaction process, the oxidation signals of TMZ, guanine and adenine were measured using differential pulse voltammetry (DPV) and PGE and accordingly, the changes at the oxidation signals were evaluated. The detection limit (DL) was also estimated based on the oxidation signal of TMZ. The interaction of TMZ with single stranded poly [A], poly [G], or double stranded poly [A]-poly[T] and poly [G]-poly[C] was also explored. Moreover, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were utilized for detection the interaction between TMZ and DNA. The features of this single-use electrochemical sensor was discussed in comparison to other reports that were developed for TMZ detection.

Fundamentals, achievements and challenges in the electrochemical sensing of pathogens.

Electrochemical sensors are powerful tools widely used in industrial, environmental and medical applications. The versatility of electrochemical methods allows for the investigation of chemical composition in real time and in situ. Electrochemical detection of specific biological molecules is a powerful means for detecting disease-related markers. In the last 10 years, highly-sensitive and specific methods have been developed to detect waterborne and foodborne pathogens. In this review, we classify the different electrochemical techniques used for the qualitative and quantitative detection of pathogens. The robustness of electrochemical methods allows for accurate detection even in heterogeneous and impure samples. We present a fundamental description of the three major electrochemical sensing methods used in the detection of pathogens and the advantages and disadvantages of each of these methods. In each section, we highlight recent breakthroughs, including the utilisation of microfluidics, immunomagnetic separation and multiplexing for the detection of multiple pathogens in a single device. We also include recent studies describing new strategies for the design of future immunosensing systems and protocols. The high sensitivity and selectivity, together with the portability and the cost-effectiveness of the instrumentation, enhances the demand for further development in the electrochemical detection of microbes.

A high performance nonenzymatic electrochemical glucose sensor based on polyvinylpyrrolidone-graphene nanosheets-nickel nanoparticles-chitosan nanocomposite.

In this report, a new nanocomposite was successfully synthesized by chemical deposition of nickel nanoparticles (NiNPs) on polyvinylpyrrolidone (PVP) stabilized graphene nanosheets (GNs) with chitosan (CS) as the protective coating. The as obtained nanocomposite (PVP-GNs-NiNPs-CS) was characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Benefiting from the synergistic effect of GNs (large surface area and high conductivity), NiNPs (high electrocatalytic activity towards the glucose oxidation) and CS (good film-forming and antifouling ability), a nonenzymatic electrochemical glucose sensor was established. The nanocomposite displays greatly enhanced electrocatalytic activity towards the glucose oxidation in NaOH solution. The PVP-GNs-NiNPs-CS based electrochemical glucose sensor demonstrates good sensitivity, wide linear range (0.1 µM-0.5 mM), outstanding detection limit (30 nM), attractive selectivity, good reproducibility, high stability as well as prominent feasibility for the real sample analysis. The proposed experiment might open up a new possibility for widespread use of non-enzymatic sensors for monitoring blood glucose owing to its advantages of low cost, simple preparation and excellent properties for glucose detection.

A Distributed Amplifier System for Bilayer Lipid Membrane (BLM) Arrays With Noise and Individual Offset Cancellation.

Lipid bilayer membrane (BLM) arrays are required for high throughput analysis, for example drug screening or advanced DNA sequencing. Complex microfluidic devices are being developed but these are restricted in terms of array size and structure or have integrated electronic sensing with limited noise performance. We present a compact and scalable multichannel electrophysiology platform based on a hybrid approach that combines integrated state-of-the-art microelectronics with low-cost disposable fluidics providing a platform for high-quality parallel single ion channel recording. Specifically, we have developed a new integrated circuit amplifier based on a novel noise cancellation scheme that eliminates flicker noise derived from devices under test and amplifiers. The system is demonstrated through the simultaneous recording of ion channel activity from eight bilayer membranes. The platform is scalable and could be extended to much larger array sizes, limited only by electronic data decimation and communication capabilities.

Electrocoagulation for the removal of phenol and aldehyde contaminants from resin effluent.

This paper is a report on a study which aimed to investigate the effect of different current density, pH, temperature, and cathode-anode combination on the removal of phenol and aldehyde in two samples of actual resin effluent through the process of electrocoagulation using solar energy. Current density 60 A/m(2) and pH 6 proved to be the best levels for both contaminants. As for the effect of temperature, although the highest degree of phenol and aldehyde removal was achieved at 15 °C, 25 °C was taken to be the optimum temperature for economic reasons. The Fe-Fe combination of electrodes was found to be the best as it led to nearly 93% of phenol removal and approximately 95% of aldehyde removal. Also, the effect of electrode combination on energy consumption was studied. It was observed that the Fe-Fe combination consumed the least amount of energy (0.7-4.3 kWh/m(3) of wastewater in the case of phenol and 0.8-4 kWh/m(3) of wastewater in the case aldehyde). Moreover, the Fe-Fe combination brought about the best results in terms of chemical oxygen demand removal: 93% in both cases. Finally, an economic analysis was performed for the electrocoagulation process.

Ultrasensitive voltammetric determination of catechol at a gold atomic cluster/poly(3,4-ethylenedioxythiophene) nanocomposite electrode.

A novel gold atomic cluster-poly(3,4-ethylenedioxythiophene) (AuAC/PEDOT/Au) nanocomposite modified gold electrode has been designed for the trace level sensing of catechol. The addition of copper(II) enhanced the electro-catalytic oxidation of catechol via the formation of copper(I). The electrochemically synthesized PEDOT/Au and the AuAC/PEDOT/Au hybrid films were characterized by electrochemical and morphological methods. Under optimal conditions the nanocomposite modified electrode offers a wider calibration range of 1 × 10(-4) to 10 µM with a lowest detection limit of 6.3 pM for catechol. Moreover, the developed electrochemical sensor exhibited good selectivity and acceptable reproducibility (1.23% for 1 nM of catechol) and could be used for the routine detection and quantification of catechol in natural water samples. To gain a better understanding of such an excellent sensor performance achieved with this electrode, studies were undertaken to pinpoint electrode kinetics of charge transfer processes.