Linear Concentration Dependence Research Articles

α-MnO2 with a cryptomelane structure for the non-enzymatic glucose electrooxidation in a neutral medium

A high demand for non-enzymatic glucose sensors and continuous glucose monitoring systems encourages the development of stable and active catalysts for the enzymeless anodic oxidation of glucose in the neutral medium. In regard to this reaction, we analyze the prospects of alpha manganese dioxide with a cryptomelane structure synthesized via an aqueous chemical route. To provide various specific surface area, the hydrated α-MnO2 oxide is annealed in a wide temperature range from 60 to 700 °C. Furthermore, we investigate the influence of the oxide annealing temperature on the amount of crystal water, chemical composition, morphology, electrochemical recharging behavior, electrocatalytic activity and stability in the glucose oxidation carried out in an isotonic NaCl-based phosphate-buffered saline (pH 7.40). To solidly determine potentials of the irreversible cathodic dissolution of α-MnO2 as well as O2/Cl2 evolution on α-MnO2, a rotating ring-disk electrode is applied. For the most active α-MnO2 sample with the 100 μg cm−2geo loading the glucose oxidation current of ca. 40 μA cm−2geo after 1 h at +0.8 V (SCE) for 7 mM of glucose is achieved. The linear concentration dependence in a physiological glucose range (1–30 mM) with the sensitivity of ca. 17.8 μA mM−0.5 cm−2geo at 25 °C is observed. Finally, glucose selectivity of α-MnO2 in relation to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol is revealed.

How to accurately quantify brain magnetic susceptibility in the context of Parkinson's disease: Validation on phantoms and healthy volunteers at 1.5 and 3 T.

Currently, brain iron content represents a new neuromarker for understanding the physiopathological mechanisms leading to Parkinson's disease (PD). In vivo quantification of biological iron is possible by reconstructing magnetic susceptibility maps obtained using quantitative susceptibility mapping (QSM). Applying QSM is challenging, as up to now, no standardization of acquisition protocols and phase image processing has emerged from referenced studies. Our objectives were to compare the accuracy and the sensitivity of 10 QSM pipelines built from algorithms from the literature, applied on phantoms data and on brain data. Two phantoms, with known magnetic susceptibility ranges, were created from several solutions of gadolinium chelate. Twenty healthy volunteers from two age groups were included. Phantoms and brain data were acquired at 1.5 and 3 T, respectively. Susceptibility-weighted images were obtained using a 3D multigradient-recalled-echo sequence. For brain data, 3D anatomical T1- and T2-weighted images were also acquired to segment the deep gray nuclei of interest. Concerning in vitro data, the linear dependence of magnetic susceptibility versus gadolinium concentration and deviations from the theoretically expected values were calculated. For brain data, the accuracy and sensitivity of the QSM pipelines were evaluated in comparison with results from the literature and regarding the expected magnetic susceptibility increase with age, respectively. A nonparametric Mann-Whitney U-test was used to compare the magnetic susceptibility quantification in deep gray nuclei between the two age groups. Our methodology enabled quantifying magnetic susceptibility in human brain and the results were consistent with those from the literature. Statistically significant differences were obtained between the two age groups in all cerebral regions of interest. Our results show the importance of optimizing QSM pipelines according to the application and the targeted magnetic susceptibility range, to achieve accurate quantification. We were able to define the optimal QSM pipeline for future applications on patients with PD.

Determination of lamotrigine in human plasma by HPLC-PDA. Application to forensic samples.

Therapeutic drug monitoring of plasma lamotrigine (LTG) has customarily been carried out in order to prevent some its adverse effects. For forensic purposes, determination of LTG in plasma is an useful tool in cases of accidental overdose or suicidal attempts. Currently, there are several analytical methods available including some based on LC tandem mass spectrometry techniques, but simple and accessible LC-UV methods still can be useful for the purpose. Here we report on a new high-performance liquid chromatography method for the determination of lamotrigine in human plasma which has been developed and validated including selectivity, sensitivity, accuracy, precision and recovery studies. Lamotrigine and the internal standard chloramphenicol were extracted from plasma using liquid-liquid extraction using small volumes of buffer and ethylacetate. Detection was monitored at 305.7 and 276.0nm for lamotrigine and chloramphenicol, respectively. The method was linear concentration dependence within the range of 0.1-10µg/ml, with a mean coefficient of correlation r = 0.993. The limit of detection (LOD) was 0.04µg/ml and the limit of quantification (LOQ) was 0.1µg/ml. Intra and interday precision values were lower than 9.0% at all concentrations studied. The intra and interday accuracy values ranged from - 7.6 to 10.1%. Recovery was found to be 98.9% or higher. The method here described was successfully applied to 11 postmortem blood samples received at the Forensic Sciences Institute of Santiago de Compostela (Spain). A new HPLC method for the determination of lamotrigine in human plasma was developed and validated. A liquid-liquid extraction using small volumes of buffer and ethylacetate was optimized. The proposed method is suitable for forensic toxicological analysis.

Сенсорное покрытие на основе липидного ленгмюровского монослоя с молекулами фермента глюкозооксидазы

A sensor coating was created based on a Langmuir monolayer of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) with immobilized molecules of the enzyme glucose oxidase and its sensor properties were studied. The process of incorporation of glucose oxidase enzyme molecules into a Langmuir monolayer of phospholipid DPPE molecules was studied using the compression isotherm method. Adsorption of glucose oxidase molecules has an expanding effect on the Langmuir monolayer of DPPE and leads to an increase in the area per molecule from 32.5 Å2 to 49 Å2 and a decrease in the compression modulus of the monolayer from 133 mN/m to 83 mN/m. Also, the adsorption of glucose oxidase leads to an increase in the desorption coefficient of the monolayer into the kd subphase from 0.5·10-3 to 1.2·10-3. The morphology of films with immobilized enzyme molecules at different adsorption times was characterized by atomic force microscopy. Increasing the enzyme adsorption time leads to a decrease in the surface roughness of the formed film from 3.6 nm at 5 minutes to 2.4 nm at 60 minutes. The formed DPPE monolayers with immobilized enzyme molecules were transferred to graphite electrodes. Their sensory properties were studied using cyclic voltammetry and impedance measurements. The resulting coatings were sensitive to glucose in solutions with concentrations from 0 to 1 mg/ml. The presence of a linear concentration dependence of the maximum and minimum currents and resistances in the specified concentration range makes the created films promising for use as touch coatings.

A new coaxial flow-through probe for electromembrane extraction of methadone from clinical samples on-line coupled to capillary electrophoresis

BackgroundA new design of a flow-through coaxial electromembrane extraction (EME) probe that can be on-line coupled with CE instrument is described and tested. The supporting base of the probe is a PDMS microchip with T-shaped channels into which two coaxially arranged capillaries for inlet and outlet solutions are inserted. The extraction part of the probe is a porous polypropylene hollow fiber, sealed at one end and modified with nitrophenyloctyl ether (NPOE) extraction fluid. The internal volume of the extraction probe is 1.1 μL. ResultsThe EME probe was tested on laboratory samples and methadone was extracted into 3.0 M AcOH as acceptor. The concentration dependence was linear in the range of 0.1–1.0 μg mL−1 at EME 300 s/150 V and in the range of 0.5–10.0 μg mL−1 at EME 100 s/150 V. The enrichment factor was greater than 30 and the LOD was 0.21 μg mL−1. The EME of methadone in clinical samples showed a linear concentration dependence in human urine and a nonlinear concentration dependence in serum. The distribution of methadone in each phase of the extraction system and the effect of extraction membrane thickness on the enrichment factor were studied. The EME probe can be applied repeatedly. SignificanceThe supporting base of EME probe and flow gating interface (FGI) are realized by a microfluidic PDMS microchips cast in the laboratory without the use of lithography. A supporting PDMS chip with coaxially arranged capillaries and extraction membrane forms a compact analytical instrument. The entire EME/CE analysis process is performed on a laboratory-made instrument and automated by LabView.

Evaluation of the multiple doses thiozonide’s pharmacokinetics in patients diagnosed with pulmonary tuberculosis with multidrug-resistant or extensively drug-resistant <i>Mycobacterium tuberculosis</i>

Relevance. The increase in the number of cases of multidrug-resistant tuberculosis (MDR-TB) determines the relevance of the development of new anti-TB drugs (ATDs). Determining the pharmacokinetics of a drug in the context of MDR-TB therapy is an integral part of the study of the original drug. Objective. Evaluation of the pharmacokinetic properties of a new original drug, thiozonide, in patients with MDR-TB with multiple doses of the drug. Methods. Thiozonide was used in patients with a verified diagnosis of MDR-TB as part of a clinical trial according to protocol No. THIO22 "Multicenter 12-week doubleblind, randomized, placebo-controlled clinical trial on the selection of optimal dosages of the drug thiozonide, capsules (CJSC Pharm-Sintez") for against the background of standard anti-tuberculosis chemotherapy in patients diagnosed with pulmonary tuberculosis with multidrug-resistant or extensively drugresistant Mycobacterium tuberculosis” (permission of the Ministry of Health of the Russian Federation No. 661 dated 11/24/2014). Results. The pharmacokinetic characteristics of thiozonide were determined during its repeated use in patients diagnosed with pulmonary tuberculosis with multidrug-resistant or extensively drug-resistant mycobacterium tuberculosis, receiving standard anti-tuberculosis chemotherapy, by HPLC with mass spectrometric detection. The time to reach the maximum concentration T max of thiozonide with repeated administration at a dose of 200 mg, 400 mg and 600 mg was 4.21 ± 1.23 hours, 4.9 ± 1.08 and 5.29 ± 0.91, respectively; the half-life T1/2 for the same dosages of the drug was 7.84 ± 1.86, 7.56 ± 1.92 and 6.3 ± 2.12 hours, respectively. The maximum concentration of thiozonide after taking the drug thiozoinide by volunteers was Cmax was observed at the level of 1386.89 ± 533.68 ng / ml in the group taking 200 mg of thiozonide per day, 2684.48 ± 712.40 when taking the drug at a dosage of 400 mg and 5558, 99 ± 2143.81 – at a dosage of 600 mg. Conclusion. A linear dependence of the maximum concentration and the area under the pharmacokinetic curve on the dose taken and also the average concentration of thiozonide in the blood plasma of patients with pulmonary tuberculosis with multidrug resistance of the causative agent of the disease was revealed.

An innovative detection technique for capillary electrophoresis: Localized terahertz emission-time domain spectroscopy

Terahertz (THz) time-domain spectroscopy (TDS) is a recently emerging analysis method which can provide unique information on molecular vibration and rotation induced by inter/intra-molecular interactions. Although the application of THz-TDS to high-performance microscale separation methods like capillary electrophoresis (CE) has been anticipated, it has been hindered due to the diffraction limit of THz wave (typically, hundreds µm). In order to realize CE-THz-TDS, in this study, we placed a narrow open-tubular capillary on the surface of a GaAs semiconductor substrate as a “localized” THz-emitter. By focusing femtosecond pulsed laser beams at the surface of a gallium arsenide (GaAs) substrate closest to the capillary, THz waves were locally generated to pass through the capillary, so that THz absorbance spectra were obtained from the capillary which has narrower inner diameter than the diffraction limit. As a typical result from acetic acid analysis in the CE-THz-TDS platform, information on the refractive index and extinction coefficient was obtained, which showed non-linear and linear concentration dependence, respectively, similar to conventional THz-TDS using large liquid cells. Finally, CE-THz-TDS analysis of several carboxylic acids was demonstrated. Two acids were successfully separated and detected with THz-TDS, where their electrophoretic mobility values were estimated as close to those obtained with conventional contactless conductivity detection. Our proposed CE-THz-TDS showed the potential for the systematic analysis of inter/intra-molecular weak interactions like hydrogen bonds, which are unable to obtain with conventional detectors.

Screen-Printed Carbon Electrodes with Cationic Cyclodextrin Carbon Nanotubes and Ferrocenyl-Carnosine for Electrochemical Sensing of Hg(II).

The study reports the use of nanoassembly based on cationic cyclodextrin carbon nanotubes (CNT-CDs) and ferrocenylcarnosine (FcCAR) for electrochemical sensing of Hg(II) in aqueous solution. β-cyclodextrins (CDs) were grafted onto CNTs by a click chemistry reaction between heptakis-(6-azido-6-deoxy)-β-cyclodextrin and alkyne-terminated CNTs. The cationic amine groups on the CD units were produced by the subsequent reduction of the residual nitrogen groups. The chemical composition and morphology of CNT-CDs were analyzed by X-ray photoelectron spectroscopy, scanning electron microscopy, and thermogravimetric analysis. A N,N-dimethylformamide dispersion of CNT-CDs was cast on the surface of screen-printed carbon electrodes (SPCEs), and the electrochemical response was evaluated by cyclic voltammetry (CV) using [Fe(CN)6]3- as the redox probe. The ability of SPCE/CNT-CD to significantly enhance the electroactive properties of the redox probe was combined with a suitable recognition element (FcCAR) for Hg(II). The electrochemical response of the CNT-CD/FcCAR nanoassembly was evaluated by CV and electrochemical impedance spectroscopy. The analytical performance of the Hg(II) sensor was evaluated by differential pulsed voltammetry and chronoamperometry. The oxidative peak current showed a linear concentration dependence in the range of 1-100 nM, with a sensitivity of 0.12 μA/nM, a limit of detection of 0.50 nM, and a limit of quantification of 1 nM.

Adsorptive stripping voltammetric determination of carbofuran in food using novel type of modified carbon-based electrode with grafted layers of nickel

A voltammetric determination of carbofuran (CBF) was developed using a novel type of carbon-containing electrode (CCE) modified with carbon ink (CI) and a chromatographic sorbent (CS) based of chromaton (Ch), polyethylene glycol and nickel acetylacetonate with grafted layers of nickel (NiCS, stands for Ni modified CS) further denoted as CI/NiCS/CCE. The surface morphology of this modified electrode was investigated by scanning electron microscopy (SEM) and by electrochemical impedance spectroscopy (EIS). CBF which is not electrochemically oxidizable was first hydrolyzed in alkaline medium to give anodically active phenolic analogue CBFP. The electrochemical reactions of CBFP at CI/NiCS/CCE were studied in phosphate buffer (PB) by cyclic voltammetry (CV) and linear sweep adsorptive stripping voltammetry (LSAdSV) using linear scan voltammetry in the first derivative mode (LSVFD). Linear concentration dependences in the concentration ranges from 0.1 to 10 μM and from 10 to 100 μM were obtained by the LSAdSV with limit of detection (LOD) and limit of quantification (LOQ) 0.06 and 0.19 μM, respectively. The novel modified CI/NiCS/CCE showed good stability and selectivity and was successfully used to determine CBF in real samples of vegetables and fruits with LOD 0.01 mg kg−1.

Fast Screening Test of Apple Juice and Surface Water for Patulin Recognition and Quantification

Since a high concentration of patulin causes cytotoxicity, a new approach to the determination of patulin plays an important role in the research and development of new control technologies. The main objective of the paper is to provide a fast screening method for obtaining clean water and high-quality apple juice. Square-wave voltammetry method using a modified Mn (OAP) Cl screen-printed carbon electrode was used for the fast screening test of apple juice and surface water for patulin recognition and quantification. A number of experimental parameters, such as scan rate, type of buffer solution, and pH, were studied and optimized. Thus, a linear concentration dependence was determined in the range 1.00 × 10–12 to 1.00 × 10–8 mol L–1, while the quantification limit was 1.00 × 10–12 mol L–1 and the detection limit was 3.33 × 10–13 mol L–1. High reliability was achieved at the assay of patulin in water and apple juice samples, with a recovery rate of 96.27–99.88%, relative standard deviation (RSD), and a bias value of less than 5.00%. Based on the remarkable outcomes, it can be inferred that the sensor holds promise as a robust instrument for point-of-care detection in the times ahead.

Electrochemical Properties and Perspectives of Nickel(II) and Cobalt(II) Coordination Polymers-Aspects and an Application in Electrocatalytic Oxidation of Methanol

The electrochemical sensing potential of two isostructural one-dimensional nickel(II) and cobalt(II) coordination polymers with 4,4′-bipyridine (4,4′-bpy) and 6-oxonicotinate (6-Onic), namely, {[Ni(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n and {[Co(4,4′-bpy)(H2O)4](6-Onic)2×2H2O}n, was investigated along with the polymers’ potential applications in the catalytic oxidation of methanol. The highly oxidative species from redox pairs Ni(II)/Ni(III) and Co(II)/Co(III) in these compounds represent catalytically active centres for oxidation of small molecules. A glassy carbon electrode (GCE) modified with a Ni polymer showed stability and reproducibility in 0.1 M NaOH, while the oxidation current inc 2reased with the increasing methanol concentration, suggesting that the Ni-polymer-modified electrode possess good sensing ability with respect to methanol. The GC electrode modified with the Co polymer is not reproducible and cannot be used for electroanalytical purposes under these experimental conditions. The GC electrode modified with the Ni polymer was successfully applied in the determination of methanol. This method showed favourable linear concentration dependence with a good sensitivity of 2.65 and 11.0 mA mM−1, a wide concentration range (0.001–4 mM), and a detection limit of 0.8 μM, which indicates its excellent application potential for methanol oxidation and thus its determination.

Array of Miniaturized Amperometric Gas Sensors Using Atomic Gold Decorated Pt/PANI Electrodes in Room Temperature Ionic Liquid Films.

Miniaturized sensors possess many advantages, such as rapid response, easy chip integration, a possible lower concentration of target compound detection, etc. However, a major issue reported is a low signal response. In this study, a catalyst, the atomic gold clusters of Aun where n = 2, was decorated at a platinum/polyaniline (Pt/PANI) working electrode to enhance the sensitivity of butanol isomers gas measurement. Isomer quantification is challenging because this compound has the same chemical formula and molar mass. Furthermore, to create a tiny sensor, a microliter of room-temperature ionic liquid was used as an electrolyte. The combination of the Au2 clusters decorated Pt/PANI and room temperature ionic liquid with several fixed electrochemical potentials was explored to obtain a high solubility of each analyte. According to the results, the presence of Au2 clusters increased the current density due to electrocatalytic activity compared to the electrode without Au2 clusters. In addition, the Au2 clusters on the modified electrode had a more linear concentration dependency trend than the modified electrode without atomic gold clusters. Finally, the separation among butanol isomers was enhanced using different combination of room-temperature ionic liquids and fixed potentials.

Spectral-fluorescent and photochemical study of 6,6′-di(benzoylamino)trimethine cyanine dyes in solutions as possible probes for DNA

Spectral-fluorescent and photochemical properties of trimethine cyanine dyes T-304, T-306, and T-307, having substituents in 6,6′-positions, in various organic solvents, in aqueous buffer solutions, in the presence of surfactants and ethanol additives, and the effect on these properties of addition of DNA have been studied. Strong aggregation of the dyes in aqueous and aqueous buffer solutions has been shown. This is due to increased hydrophobicity of the dyes, which makes it difficult to use them as spectral-fluorescent probes for DNA. In the presence of DNA, trimethine cyanines partially form highly fluorescent complexes of dye monomers with the biomolecule, with slight decomposition of the initial aggregates and the formation of aggregates on DNA molecules. The formation of different types of dye–DNA complexes, i.e., intercalation and binding in the DNA grooves, was modeled by molecular docking. Dye–DNA complexes were also studied by circular dichroism spectroscopy and by thermal dissociation of DNA. To reveal selectivity of the dyes, their interaction with human serum albumin was briefly studied. The presence of moderate concentrations of nonionic surfactants does not lead to a significant decomposition of aggregates, but leads to a biphasic dependence of the fluorescence intensity on the DNA concentration. At the same time, ethanol additives (15%) lead to a more or less linear concentration dependence of the fluorescence intensity, which makes it possible to use these dyes as fluorescent probes for DNA. The effective binding constants of the dyes to DNA and the limits of DNA detection using the dyes in the presence of 15% ethanol were estimated. Photoisomerization and generation of the triplet states of T-304, T-306, and T-307 have been also studied. Along with the fluorescence growth, complexation with DNA leads to an increase in the yield of the triplet states of the dyes. This creates a prerequisite for using the dyes in targeted PDT. In the presence of DNA, the decay kinetics of the triplet states are biexponential, which indicates different types of dye complexes with DNA. The rate constants of oxygen quenching of the triplet states of the dyes bound to DNA are significantly lower than the diffusion-controlled values (taking into account the spin-statistical factor), which is explained by the shielding effect on the triplet molecules in complexes with DNA. The data obtained show that dyes T-304, T-306 and T-307, with addition of 15% ethanol, can be used as possible fluorescent probes for DNA.

Gap bowing of in Pb1-xCaxS, Pb1-xCaxSe and Pb1-xCaxTe alloys

The ab initio full potential linearized augmented plane wave (FP-LAPW) method within density func­tional theory was applied to study the effect of composition on the structural and electronic properties of Pb1-xCaxS, Pbl-xCaxSe and Pb1-xCaxTe temary alloys. The effect of composition on lattice parameter, bulk modulus, band gap was investigated. Deviations of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence were observed for all three alloys. In addi­tion, the microscopic origins of compositional disorder were explained by using the approach of Zunger and co-workers. The disorder parameter (gap bowing) was found to be strong for the three alloys and was mainly caused by the chemical charge transfer effect. The volume deformation contributions for all alloys were also found to be significant, while the structural relaxation contributions to the gap bowing parameter were relatively smaller for all alloys.

Determination of sugar content in honey using LC-Raman and programmable pump-Raman methods.

We combined (i) liquid chromatography and Raman spectrometry (LC-Raman) and (ii) programmable pump and Raman spectrometry (PP-Raman) to separate and identify compounds in a mixture. These techniques were applied to conduct a quantitative analysis of the sugars in honey. The spectral and temporal axes of the LC-Raman data were analyzed using the MCR-ALS analysis procedure, which enabled the separation and identification of four sugars (glucose, fructose, sucrose, and trehalose). The PP-Raman method was employed to examine the sugar concentration dependence of the intensity pattern of the Raman spectrum, and the linear concentration dependence of the intensity was obtained. The sugar contents were quantitatively determined from the integrated area of the elution peaks. The result was consistent with those derived from mass spectrometry and previous studies. The origin of the errors in the derived sugar contents is discussed. Our study presents a novel quantitative LC-Raman spectrometric method that does not rely on resonance or surface enhancement effects.

The Voltammetric Detection of Cadaverine Using a Diamine Oxidase and Multi-Walled Carbon Nanotube Functionalised Electrochemical Biosensor

Cadaverine is a biomolecule of major healthcare importance in periodontal disease; however, current detection methods remain inefficient. The development of an enzyme biosensor for the detection of cadaverine may provide a cheap, rapid, point-of-care alternative to traditional measurement techniques. This work developed a screen-printed biosensor (SPE) with a diamine oxidase (DAO) and multi-walled carbon nanotube (MWCNT) functionalised electrode which enabled the detection of cadaverine via cyclic voltammetry and differential pulse voltammetry. The MWCNTs were functionalised with DAO using carbodiimide crosslinking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS), followed by direct covalent conjugation of the enzyme to amide bonds. Cyclic voltammetry results demonstrated a pair of distinct redox peaks for cadaverine with the C-MWCNT/DAO/EDC-NHS/GA SPE and no redox peaks using unmodified SPEs. Differential pulse voltammetry (DPV) was used to isolate the cadaverine oxidation peak and a linear concentration dependence was identified in the range of 3-150 µg/mL. The limit of detection of cadaverine using the C-MWCNT/DAO/EDC-NHS/GA SPE was 0.8 μg/mL, and the biosensor was also found to be effective when tested in artificial saliva which was used as a proof-of-concept model to increase the Technology Readiness Level (TRL) of this device. Thus, the development of a MWCNT based enzymatic biosensor for the voltammetric detection of cadaverine which was also active in the presence of artificial saliva was presented in this study.

Main Metabolites of Pseudomonas aeruginosa: A Study of Electrochemical Properties.

Pseudomonas aeruginosa is a ubiquitously distributed soil and water bacterium and is considered an opportunistic pathogen in hospitals. In cystic fibrosis patients, for example, infections with P. aeruginosa can be severe and often lead to chronic or even fatal pneumonia. Therefore, rapid detection and further identification are of major importance in hospital hygiene and infection control. This work shows the electrochemical properties of five P. aeruginosa key metabolites considering their potential use as specific signaling agents in an electrochemical sensor system. The pure solutes of pyocyanin (PYO), Pseudomonas quinolone signal (PQS), pyochelin (PCH), 2-heptyl-4-hydroxyquinoline (HHQ), and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) were analyzed by different electrochemical techniques (cyclic and square wave voltammetry) and measured using a Gamry Reference 600+ potentiostat. Screen-printed electrodes (DropSens DRP110; carbon working and counter, silver reference electrode) were used to determine signal specificities, detection limits, as well as pH dependencies of the substances. All of the compounds were electrochemically inducible with well-separated oxidation and/or reduction peaks at specific peak potentials relative to the reference electrode. Additionally, all analytes exhibited linear concentration dependency in ranges classically reported in the literature. The demonstration of these properties is a promising step toward direct multiplexed detection of P. aeruginosa in environmental and clinical samples and thus, can make a significant contribution to public health and safety.

The surface alloying of aluminum with Sn and Pb for enhancement mechanism under high current pulsed electron beam

The purpose of this study is to investigate the solid solution strengthening (SSS) of Sn, Pb in aluminum (Al) matrix under high current pulses electron beam (HCPEB) irradiation. First-principles calculations method was adopted to quantify the effect of SSS with various concentrations. The capacity to strengthen is correlated with a nearly linear concentration dependency. In experimental section, the microstructures of the Pb/ and Sn/Al systems were characterized by SEM and TEM analysis. The solubility limit of both systems under HCPEB irradiation were calculated by a simple thermodynamic model. It is found that the Sn/Al system has a higher solid solubility, compared to that of the Pb/Al. In addition, the values of SSS of the Pb/ and Sn/Al systems were estimated. The results show that the Sn/Al system has higher strengthening ability than that of the Pb/Al system under HCPEB irradiation due to the different solid solubility, which is consistent with theory.

A Rapid Graphene Sensor Platform for the Detection of Viral Proteins in Low Volume Samples

Infectious disease outbreaks remain an ever‐prevalent global issue. The associated demand for rapid diagnostics and onsite testing will play an increasing and critical role in disease surveillance, prevention of the spread of infection, as well as timely commencement of treatment. Reported here is a graphene–gold nanoparticle hybrid sensor platform technology that is demonstrated for the real‐time detection of viral proteins utilizing low volume samples (5 μL). Hepatitis C virus (HCV) is still an endemic problem worldwide and is used as an exemplar system here to demonstrate the capability of the platform viral detection sensor technology. Hepatitis C virus core antigen (HCVcAg) is a promising marker for point‐of‐care (POC) diagnostic testing for active HCV infection, with the potential to provide a one‐stop diagnosis and trigger for the commencement of treatment. Real‐time electrical resistance measurements are performed using various concentrations of HCVcAg with linear concentration dependence of resistance on HCVcAg concentration over the range of 100–750 pg mL−1.

A low-fouling and reusable biosensor for the sensitive electrochemical assay of tuberculosis gene

A low-cost, portable, and reusable biosensor for the rapid and selective quantitation of tuberculosis (TB) gene with low expression levels in early-stage serum specimens is highly desirable but remains a challenge. Herein, a novel biosensor was fabricated using the layer-by-layer assembly of gold nanoparticles (Au NPs), polyethylenimine (PEI) and chondroitin sulfate (CS). The synergistic effect of PEI and CS endows this biosensor antifouling properties towards single proteins, even towards complex biological systems. Before and after the incubation in 10% serum, only 6.4% peak current change of DPV response was obtained. To the best of our knowledge, a few examples have been reported on the successful application of CS in mitigating biofouling. Next, a special gene only representing TB was modified on CS-modified electrode, and this biosensor showed a fast response with good linear concentration dependence on the target DNA in the range 10−14 M to 10−10 M. More importantly, this biosensor based on the reversible bonding of DNA double strand could be reused for at least four times after the regeneration of urea without any passivation, which further reduced the cost of the entire strategy. To some extent, this indicates that the CS-modified biosensor has certain practical application prospect and can be extended to fabricate similar biosensors for the detection of other diseases.