Portable Electrochemical Analyzer Research Articles

Portable and Flexible Hydrogel Sensor for On-Site Atrazine Assay on Agricultural Products.

There is growing attention focused toward the problems of ecological sustainability and food safety raised from the abuse of herbicides, which underscores the need for the development of a portable and reliable sensor for simple, rapid, and user-friendly on-site analysis of herbicide residues. Herein, a novel multifunctional hydrogel composite is explored to serve as a portable and flexible sensor for the facile and efficient analysis of atrazine (ATZ) residues. The hydrogel electrode is fabricated by doping graphite-phase carbon nitride (g-C3N4) into the aramid nanofiber reinforced poly(vinyl alcohol) hydrogel via a simple solution-casting procedure. Benefiting from the excellent electroactivity and large specific surface area of the solid nanoscale component, the prepared hydrogel sensor is capable of simple, rapid, and sensitive detection of ATZ with a detection limit down to 0.002 ng/mL and per test time less than 1 min. After combination with a smartphone-controlled portable electrochemical analyzer, the flexible sensor exhibited satisfactory analytical performance for the ATZ assay. We further demonstrated the applications of the sensor in the evaluation of the ATZ residues in real water and soil samples as well as the user-friendly on-site point-of-need detection of ATZ residues on various agricultural products. We envision that this flexible and portable sensor will open a new avenue on the development of next-generation analytical tools for herbicide monitoring in the environment and agricultural products.

Self-assembled multilayer Nb2C MXene/MnFe2O4 electrochemical sensor with Schottky junctions for the detection of acetaminophen and dopamine

The electrochemical sensors with the ability of biomolecule detection can be used for human life and health monitoring. In this work, we developed an electrochemical sensor with a Schottky junction by electrostatic interaction, composed of Nb2C MXene and MnFe2O4. Large reactive groups (O, OH, Cl, or F) are observed at the ends of the Nb2C MXene surface. Meanwhile, there are abundant oxygen vacancies and surfaces of MnFe2O4 which bring it favorable heterogeneous catalytic properties. Among them, the chemical self-assembly of MnFe2O4 nanoparticles on Nb2C MXene enhances the binding strength of the material through electrostatic interaction, promotes charge transfer across the interface, and modulates the electronic and nanostructural characteristics of the N-MFO (MnFe2O4/Nb2C MXene). The results demonstrate that the sensing performance of N-MFO4 for Acetaminophen (AP) and Dopamine (DA) is significantly improved compared to Nb2C MXene and MnFe2O4 modified electrodes, respectively. The obtained limits of detection (LOD) of N-MFO4 modified electrode for AP and DA being 0.079 and 0.070 μM, respectively. The combination of electrodes modified with highly active nanomaterials is supposed to build a portable electrochemical analysis system with high sensitivity, good selectivity, favorable stability, simple operation and low cost, and promote the application of electrochemical sensors in related fields.

Laser-enabled flexible electrochemical sensor on finger for fast food security detection

Today’s rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO2 laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 μM and the linear range of 10–200, 5–80 and 25–250 μM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 μM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 μM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain.

A stretchable glove sensor toward rapid monitoring of trifluralin: A new platform for the on-site recognition of herbicides based on wearable flexible sensor technology using lab-on-glove.

In this study, a flexible glove-based electrochemical sensor as a wearable point-of-use screening tool has been fabricated for defense and food security applications. To design the wearable glove-based sensor, we drew conductive patterns on the fingers of a rubber glove via gold@silver-modified graphene quantum dots (Au@Ag core-shell/graphene quantum dots [GQDs]) nano-ink with optimal thickness. Then, this platform is combined with a portable electrochemical analyzer for on-site detection of trifluralin pesticide in the range of 10nM to 1 mM with the low limit of quantification (LLOQ) of 10nM. The high efficiency and distinction of the trifluralin at specified concentrations in real leaf and apple samples were performed by simply touching with the glove and in spikes solution by immersing of fingertips. With their high sensitivity, selectivity, rapid, and easy operation pesticide analysis, these glove-embedded sensors can also be engaged in on-site monitor of other chemical threats and can be expanded to water and environmental samples.

Hyperreactivity of the bronchi in children, whooping cough convalescents

Objective:to assess the presence and degree of bronchial hyperreactivity in convalescents of whooping cough based on the results of bronchial provocation tests.Materials and methods. Using bronchial provocative samples with a 0,02/0,33% histamine solution and 0,33% methacholine solution on a PROVOTEST-2 apparatus from PARI, bronchial hyperreactivity was studied in 12 pertussis convalescents aged 7 to 17 years. The level of endogenous nitrogen monoxide in exhaled air (FeNO) was measured using a portable NObreath electrochemical analyzer (from Bedfont Scientific Ltd.).The results.According to the results of BPP, 6 of 12 convalescents of whooping cough were found to have bronchial hyperreactivity of varying degrees. When conducting a breath test with a histamine solution, bronchial hyperreactivity was recorded in three children, in a sample with methacholine, in five. In 3 out of 6 children with revealed signs of bronchial hyperreactivity, the history of atopy was not burdened, which suggests a connection between the pertussis and the development of bronchial hyperreactivity. A significant increase in the level of endogenous nitric monoxide (above 16 ppb) was observed in 2 out of 10 patients. Follow-up observation showed that the duration of cough with whooping cough ranged from 3 to 6 months, and in patients with positive results of several tests it was maximum. Two out of three children with bronchial asthma showed elevated levels of FeNO and samples with methacholine. Follow-up observation showed that whooping cough aggravated bronchial asthma and demanded correction therapy.Conclusion. A pilot study on the evaluation of bronchial provocative tests suggests that the formation of bronchial hyperreactivity in convalescents of whooping cough is probable, including without a history of atopy, which increases the risk of developing bronchial asthma, however, additional studies are required for a final conclusion.

The Role of FENO in Comparison to Spirometry and ACT in Control of Children Asthma Symptoms.

Fractional exhaled nitric oxide (FeNO) is a noninvasive marker of inflammation, used for monitoring asthma. The aim of this study was to compare FeNO, asthma control test (ACT), and lung function test (spirometry) in children aged 8-15 years. This observational, cross-sectional study was performed on76 asthmatic children (age, 8-15 years), who were referred to the Department of Immunology and Allergy, Children's Medical Center, Tehran, Iran during 2012-2013. Patients were matched for sex and age. The recruited patients were selected via consecutive sampling. FeNO was measured with a portable electrochemical analyzer and forced spirometry was performed according to the American Thoracic Society (ATS) guidelines. The ACT questionnaire was used and completed for all the patients.The mean FeNO was 28.5±29.1 ppb, and the mean ACT score was 19.8±3.6. FeNO was significantly correlated with forced expiratory volume (FEV1) (r, 0.232; p=0.049) or 25-75% maximum expiratory flow (MEF 25-75) (r, -0.304; p=0.009). FeNO showed no significant correlation with ACT score or FEV1/forced vital capacity (FVC) (p>0.05). Additionally, there was no significant correlation between FeNO and changes in FEV1 and MEF 25-75% before and after the administration of bronchodilators (p>0.05). To improve asthma control, childhood ACT, FeNO, and spirometric tests can be used as complementary tools in clinical practice to detect children with poorly controlled asthma.

Wearable electrochemical glove-based sensor for rapid and on-site detection of fentanyl

Rapid, on-site detection of fentanyl is of critical importance, as it is an extremely potent synthetic opioid that is prone to abuse. Here we describe a wearable glove-based sensor that can detect fentanyl electrochemically on the fingertips towards decentralized testing for opioids. The glove-based sensor consists of flexible screen-printed carbon electrodes modified with a mixture of multiwalled carbon nanotubes and a room temperature ionic liquid, 4-(3-butyl-1-imidazolio)-1-butanesulfonate. The sensor shows direct oxidation of fentanyl in both liquid and powder forms with a detection limit of 10 μM using square-wave voltammetry. The “Lab-on-a-Glove” sensors, combined with a portable electrochemical analyzer, provide wireless transmission of the measured data to a smartphone or tablet for further analysis. The integrated sampling and sensing methodology on the thumb and index fingers, respectively, enables rapid screening of fentanyl in the presence of a mixture of cutting agents and offers considerable promise for timely point-of-need screening for first responders. Such a glove-based “swipe, scan, sense, and alert” strategy brings chemical analytics directly to the user's fingertips and opens new possibilities for detecting substances of abuse in emergency situations.

Simultaneous detection of glucose, uric acid and cholesterol using flexible microneedle electrode array-based biosensor and multi-channel portable electrochemical analyzer

The development of versatile and low-cost biosensor system for rapid and simultaneous detection of multiple blood metabolites is highly demanded for home healthcare. We developed a flexible microneedle electrode array-based biosensor (MEAB) and a multi-channel portable electrochemical analyzer (MPEA) for the simultaneous detection of glucose, uric acid, and cholesterol. Microneedle electrode array (MEA) was fabricated on the flexible substrate using magnetorheological drawing lithography, followed by sputter coated with Au/Ti film. Then, through biofunctionalized with glucose oxidase, uricase and cholesterol oxidase, MEA was conditioned as a biosensor for simultaneous detection of glucose, uric acid and cholesterol. MEAB demonstrated excellent sensing performance with a wide linear range (glucose, 2–12 mM; uric acid, 0.1–1.2 mM; cholesterol, 1–12 mM), low detection limit (glucose, 260 μM; uric acid, 4 μM; cholesterol, 440 μM), and rapid response time (∼4 s). MPEA, a homemade ARM STM32 microcontroller-based electrochemical analyzer, was validated to be comparable to that of the commercial electrochemical workstation. MPEA integrated with flexible MEAB could accurately and simultaneously detect glucose, uric acid, and cholesterol levels in serum, and the results were consistent with the portable electrochemical device. The ease-of-use of the reported biosensor system will facilitate effective monitoring of blood metabolites at home.

A rapid on-site analysis method for the simultaneous extraction and determination of Pb2+ and Cd2+ in cereals.

In order to achieve rapid on-site screening and solve the problem of rapid pretreatment for the determination of lead (Pb2+) and cadmium (Cd2+) in cereals by a portable electrochemical analyzer with disposable screen-printed electrodes (SPEs), a new reliable and simple extraction method for Pb2+ and Cd2+ in cereals was developed. The Pb2+ and Cd2+ in cereals were purified by a mixed solution of 1 mol L−1 potassium iodide (KI)/5% vitamin C (VC)/ethyl acetate after being extracted by 10% HNO3, which transfers the Pb2+ and Cd2+ into ethyl acetate after a reaction with KI–VC. Then, the Pb2+ and Cd2+ were eluted from ethyl acetate with 5% HNO3 and were determined by an electrochemical analyzer with screen printed electrodes. Under the optimized conditions, the matrix calibration curves of Pb2+ and Cd2+ in rice and wheat showed good linear relationships with R2 > 0.996. The method shows a detection limit (LOD) for Cd2+ in rice and wheat of 6.7 μg kg−1 and 11.5 μg kg−1, and the corresponding values for Pb2+ were 34.9 and 31.1 μg kg−1, respectively. The relative standard deviation (RSD) was less than 8.7% for Cd2+ and Pb2+. In addition, the recoveries of the tested reference materials using this method were between 80% and 120%. From sample pretreatment to testing results, the whole process took no more than 25 min, and the operation was simple for operators, green to the environment, cheap in terms of instruments, and above all suitable for on-site detection. The results implied that this portable electrochemical method with new pretreatment may be a good choice for screening Pb2+ and Cd2+ in cereal samples on-site.

Biological Oxygen Demand in Soils and Litters

Biological oxygen demand (BOD) in mineral and organic horizons of soddy-podzolic soils in the forest-park belt of Moscow as an indicator of their microbial respiration and potential biodestruction function has been studied. The BOD of soil samples has been estimated with a portable electrochemical analyzer after incubation in closed flasks under optimum hydrothermal conditions. A universal gradation scale of this parameter from very low ( 140 g O2/(m3 h)) has been proposed for mineral and organic horizons of soil. A physically substantiated model has been developed for the vertical distribution of BOD in the soil, which combines the diffusion transport of oxygen from the atmosphere and its biogenic uptake in the soil by the first-order reaction. An analytical solution of the model in the stationary state has been obtained; from it, the soil oxygen diffusivity and the kinetic constants of O2 uptake have been estimated, and the profile-integrated total BOD value has been calculated (0.4–1.8 g O2/(m2 h)), which is theoretically identical to the potential oxygen flux from the soil surface due to soil respiration. All model parameters reflect the recreation load on the soil cover by the decrease in their values against the control.

Handheld isothermal amplification and electrochemical detection of DNA in resource-limited settings

This paper demonstrates a new method for electrochemical detection of specific sequences of DNA present in trace amounts in serum or blood. This method is designed for use at the point-of-care (particularly in resource-limited settings). By combining recombinase polymerase amplification (RPA)— an isothermal alternative to the polymerase chain reaction — with an electroactive mediator, this electrochemical methodology enables accurate detection of DNA in the field using a low-cost, portable electrochemical analyzer (specifically designed for this type of analysis). This handheld device has four attributes: (1) It uses disposable, paper-based strips that incorporate screen-printed carbon electrodes; (2) It accomplishes thermoregulation with ±0.1 °C temperature accuracy; (3) It enables electrochemical detection using a variety of pulse sequences, including square-wave and cyclic voltammetry, and coulometry; (4) It is operationally simple to use. Detection of genomic DNA from Mycobacterium smegmatis (a surrogate for M. tuberculosis—the main cause of tuberculosis), and from M. tuberculosis itself down to ∼0.040 ng/μL provides a proof-of-concept for the applicability of this method of screening for disease using molecular diagnostics. With minor modifications to the reagents, this method will also enable field monitoring of food and water quality.

Comparison of fractional exhaled nitric oxide levels measured using the NIOX VERO and NOA 280i

Fractional exhaled nitric oxide (FeNO) is a type 2 biomarker of eosinophilic airway inflammation and predicts the likelihood of corticosteroid responsiveness in patients with eosinophilic asthma. 1 Dweik R.A. Boggs P.B. Erzurum S.C. et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications. Am J Respir Crit Care Med. 2011; 184: 602-615 Crossref PubMed Scopus (1805) Google Scholar , 2 Robinson D. Humbert M. Buhl R. et al. Revisiting type 2-high and type 2-low airway inflammation in asthma: current knowledge and therapeutic implications. Clin Exp Allergy. 2017; 47: 161-175 Crossref PubMed Scopus (247) Google Scholar Several devices are available to measure FeNO levels for research purposes or in clinical practice worldwide, including the Sievers Nitric Oxide Analyzer (NOA 280i; GE Analytical Instruments, Boulder, Colorado), a stationary chemiluminescence analyzer, and the NIOX VERO (Aerocrine AB, Solna, Sweden), a portable electrochemical analyzer. The NIOX VERO is a new FeNO measurement device that is intended to replace the NIOX MINO, a previous portable electrochemical analyzer from the same manufacturer. [3] National Institute for Health and Care Excellence. Measuring fractional exhaled nitric oxide concentration in asthma. NICE diagnostics guidance 12. www.nice.org.uk/dg12. Accessed August 24, 2017. Google Scholar Some reports have compared the NOA 280i with the NIOX MINO. 4 Kim S.H. Moon J.Y. Kwak H.J. et al. Comparison of two exhaled nitric oxide analyzers: the NIOX MINO hand-held electrochemical analyzer and the NOA280i stationary chemiluminescence analyzer. Respirology. 2012; 17: 830-834 Crossref PubMed Scopus (33) Google Scholar , 5 Maniscalco M. de Laurentiis G. Weitzberg E. et al. Validation study of nasal nitric oxide measurements using a hand-held electrochemical analyser. Eur J Clin Invest. 2008; 38: 197-200 Crossref PubMed Scopus (41) Google Scholar However, potential differences between the NOA 280i and NIOX VERO remain unclear. In this cross-sectional study, we compared FeNO levels measured using the NOA 280i and NIOX VERO.

Guidelines for evaluation and treatment of lead poisoning of wild raptors

ABSTRACTLead poisoning is a threat to birds, particularly scavenging birds of prey. With the availability of portable lead‐testing kits, an increasing number of field researchers are testing wild‐caught birds, in situ, for lead poisoning. We describe guidelines for evaluation of lead toxicity in wild raptors by outlining field testing of blood‐lead concentrations, presenting criteria for removing a lead‐poisoned bird from the wild for treatment, and suggesting strategies for effective treatment of lead intoxicated raptors. Field testing of birds is most commonly accomplished via portable electrochemical analysis of blood; visual observation of condition alone may provide insufficient evidence upon which to make a decision about lead poisoning. Our intended audience is not only the avian research community, but also rehabilitation facilities that may receive apparently uninjured birds. Best practices suggest that birds whose blood‐lead levels are <40 μg/dL be released back to the wild as soon as possible after capture. The decision to release or treat birds with blood‐lead levels between 40 μg/dL and 60 μg/dL should be made based on the presence of clinical signs of poisoning and relevant biological characteristics (e.g., breeding status). Finally, birds with blood‐lead levels >60 μg/dL are potentially lethally poisoned and best served if removed from the wild for appropriate treatment at a licensed rehabilitation facility and later released. We present guidelines for decision‐making when treating lead poisoning of wild raptors. Future work based on experimental studies will clarify the role of lead poisoning for specific species and be important to refine these guidelines to improve effectiveness. © 2017 The Wildlife Society.

ARM-microcontroller based portable nitrite electrochemical analyzer using cytochrome c reductase biofunctionalized onto screen printed carbon electrode

Nitrite (NO2−) supplementation limits hypoxia-induced oxidative stress and activates the alternate NO pathway which may partially account for the nitrite-mediated cardioprotection. So, sensitive and selective biosensors with point-of-care devices need to be explored to detect the physiological nitrite level due to its important role in human pathophysiology. In this work, cytochrome c reductase (CcR) biofunctionalized self assembled monolayer (SAM) functionalized on gold nanoparticles (GNPs) in polypyrrole (PPy) nanocomposite onto the screen printed carbon electrode (SPCE) was investigated as a biosensor for the detection of nitrite based on its electrochemical and catalytic properties. CcR was covalently coupled with SAM layers on GNPs by using EDC and NHS. Direct electrochemical response of CcR biofunctionalized electrodes showed a couple of well-defined and nearly reversible cyclic voltammetric peaks at −0.34 and −0.45 vs. Ag/AgCl. Under optimal conditions, the biosensor could be used for the determination of NO2− with a linear range from 0.1–1600µm and a detection limit of 60nM with a sensitivity of 0.172µAµM−1cm–2. Further, we have designed and developed a novel and cost effective portable electrochemical analyzer for the measurement of NO2− in hypoxia induced H9c2 cardiac cells using ARM microcontroller. The results obtained here using the developed portable electrochemical nitrite analyzer were also compared with the standard cyclic voltammetry instrument and found in agreement with each other.

Development of a Novel Cu(II) Complex Modified Electrode and a Portable Electrochemical Analyzer for the Determination of Dissolved Oxygen (DO) in Water

The development of an electrochemical dissolved oxygen (DO) sensor based on a novel Cu(II) complex-modified screen printed carbon electrode is reported. The voltammetric behavior of the modified electrode was investigated at different scan rates and oxygen concentrations in PBS (pH = 7). An increase of cathodic current (at about −0.4 vs. Ag/AgCl) with the addition of oxygen was observed. The modified Cu(II) complex electrode was demonstrated for the determination of DO in water using chronoamperometry. A small size and low power consumption home-made portable electrochemical analyzer based on custom electronics for sensor interfacing and operating in voltammetry and amperometry modes has been also designed and fabricated. Its performances in the monitoring of DO in water were compared with a commercial one.

Disposable carbon electrodes as an alternative for the direct voltammetric determination of alkyl phenols from water samples

Disposable sensors based on a pencil graphite electrode were described for detection of alkyl phenols. The performances of the disposable bare pencil graphite electrode (PGE) and PGE modified with carbon nanotubes, regarding the cyclic and differential pulse voltammetric determination of 4-nonylphenol, 4-octylphenol, and 4-tert-octylphenol, were compared. Some experimental variables of the electrode surface pretreatment and measurement parameters were optimized. Using a phosphate buffer solution (pH 7.40) as the supporting electrolyte, alkyl phenols gave a well-defined oxidation peak at about 700 mV vs. Ag/AgCl. The detection limits established for each alkyl phenol were: 0.25 \muM for 4-octylphenol, 0.42 \muM for 4-nonylphenol, and 0.77 \muM for 4-tert-octylphenol. This method is suitable for the direct determination of the total content of these pollutants found at micromolar levels in water samples. The results obtained applying this method are in good agreement with those obtained by high-performance liquid chromatography. The developed sensor has shown some advantages such as low cost, sensitivity, and capability to generate reproducible results using a simple and direct electrochemical protocol. By using this type of commonly available disposable working electrode and a portable electrochemical analysis system, the developed method can be applied to the determination of alkyl phenols directly at the sampling point.

Cheap in situ voltammetric copper determination from freshwater samples

Detection of low concentrations of heavy metals in environmental samples is of particular interest because most of them represent persistent, highly toxic pollutants. Cu2+ detection in environmental samples is important because it is typical heavy metal, being an essential element for human beings but at higher concentrations it can create health risks. Due to the accumulation steps involved, anodic stripping voltammetry (ASV) is one of the most sensitive techniques used for the detection of low concentrations of metal ions form different environmental samples. In order to minimize sample loss during sample collection, storage and transportation it is of particular interest to perform in situ rapid and reliable routine analysis. In the present paper we describe the use of a simple, disposable pencil graphite electrode (PGE) for the determination of Cu from river water samples by mercury film anodic stripping voltammetry. The investigated water samples were collected during a period of 3 years (2009-2011), from six sampling points situated along the lower part of the Prut River (Romania). ASV measurements were performed in the presence of Hg 2+ in 0.1 M HNO3 at a carbon pencil graphite working electrode. Standard addition method was applied for the quantification of Cu 2+. The Cu 2+ content of the most river water samples analysed exceeded 2 ⎧g/L (MEWM, 2006), the maximum admitted concentration for surface waters, and these could be due to the anthropogenic activities in the region (e.g. the largest steel factory in Romania is located in the vicinity of the sampling area). Samples show an additional importance as the region is included in a protected area, Lower Prut Floodplain Natural Park, and trace elements transfer along the aquatic food chain has been previously documented (Matache et. al, 2012). The results obtained by ASV on PGE agreed well with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) using the Romanian standard SR ISO 11885-09. The sensor used in this work has shown some important advantages such being cheap, sensitive and able to generate reproducible results using a simple and direct electrochemical protocol. By using this type of disposable working electrodes and a portable electrochemical analysis system the developed method can be applied to the determination of copper ions directly at the sampling point.

An integrated electrochemical device based on immunochromatographic test strip and enzyme labels for sensitive detection of disease-related biomarkers

A novel electrochemical biosensing device that integrates an immunochromatographic test strip and a screen-printed electrode (SPE) connected to a portable electrochemical analyzer was presented for rapid, sensitive, and quantitative detection of disease-related biomarker in human blood samples. The principle of the sensor is based on sandwich immunoreactions between a biomarker and a pair of its antibodies on the test strip, followed by highly sensitive square-wave voltammetry (SWV) detection. Horseradish peroxidase (HRP) was used as a signal reporter for electrochemical readout. Hepatitis B surface antigen (HBsAg) was employed as a model protein biomarker to demonstrate the analytical performance of the sensor in this study. Some critical parameters governing the performance of the sensor were investigated in detail. Under optimal conditions, this sensor was capable of detecting a minimum of 0.3ngmL−1 (S/N=3) HBsAg with a wide linear concentration range from 1 to 500ngmL−1. The sensor was further utilized to detect HBsAg spiked in human plasma with an average recovery of 91.3%. In comparison, a colorimetric immunochromatographic test strip assay (ITSA) was also conducted. The result shows that the SWV detection in the electrochemical sensor is much more sensitive for the quantitative determination of HBsAg than the colorimetric detection, indicating that such a sensor is a promising platform for rapid and sensitive point-of-care testing/screening of disease-related biomarkers in a large population.

Disposable immunosensor for human cardiac troponin T based on streptavidin-microsphere modified screen-printed electrode

Screen-printed electrodes (SPE) have been widely used in the design of disposable sensors bringing advances in the use of electrochemical immunosensors for in field-clinical analysis. In this work, streptavidin polystyrene microspheres were incorporated to the electrode surface of SPEs in order to increase the analytical response of the cardiac troponin T (cTnT), a specific biomarker for the acute myocardial infarction diagnosis. The precise calculation of the stoichiometric streptavidin–biotin ratio [1:4] allowed the increase of sensitivity and stability of the immunosensor response to the cTnT analyte. The surface of the immunosensor was characterized by scanning electron microscopy and cyclic voltammetry. It was observed that the use of streptavidin microspheres significantly increased the analytical sensitivity of the electrode in 8.5 times, showing a curve with a linear response range between 0.1 and 10 ng mL −1 of cTnT and a detection limit of 0.2 ng mL −1. The proposed SPE showed ease preparation and high sensitivity allowing the detection of cTnT in the range of clinical levels. The new device coupled with a portable electrochemical analyzer shows great promise for point-of-care quantitative testing of necrosis cardiac proteins.

Association among lung function, exhaled nitric oxide, and the CAN questionnaire to assess asthma control in children

The aim of this study was to investigate the association among a validated symptom-based questionnaire for asthma control in children (CAN), forced expiratory volume in 1 sec (FEV(1)), and fractional exhaled nitric oxide (FE(NO)). Observational cross-sectional study was performed in a consecutive sample of asthmatic children aged between 7 and 14 years old from December 2007 to February 2008. FE(NO) was measured with a portable electrochemical analyzer and forced spirometry was performed according to American Thoracic Society/European Respiratory Society. The CAN questionnaire was completed by the parents (aged <9 years old) or by the children (> or = 9 years old). The strength of the association among FEV(1), FE(NO), and CAN questionnaire was studied using Spearman's rho, and the degree of agreement for asthma control among FEV(1), FE(NO), and CAN questionnaire, with classification of these variables according to values of normality, was studied using Pearson's chi(2) test and Cohen's kappa (KC). We studied 268 children, mean age 9.7 +/- 2.1 years. Significant correlations were found between FE(NO) and CAN (r = 0.2), between FEV(1) and CAN (r = -0.3), and between FE(NO) and FEV(1) (r = -0.12). On classifying the variables according to values of normality, no agreement was found to establish the degree of asthma control between FE(NO) and CAN (KC = 0.18, chi(2) Pearson = 9.63); between FEV(1) and CAN (KC = 0.29, chi(2) = 38.5); or between FE(NO) and FEV(1) (KC = 0.07, chi(2) = 4.9). The association among the three measurement instruments used to assess asthma control (FEV(1), FE(NO), and CAN) was weak. These are instruments that quantify variables that influence asthma in different ways, in this sense, none can be used instead of another in asthma management although they are complementary.