Nanomolar Detection of Glutamate at a Biosensor Based on Screen-Printed Electrodes Modified with Carbon Nanotubes

The amperometric glutamate biosensor based on screen-printed electrodes containing carbon nanotubes (CNT), and its integration in a flow injection analysis system, is described herein. The sensor was fabricated by simply adsorbing enzyme glutamate oxidase (GlutOx) on a commercial substrate containing multi-wall CNT. The resulting device displayed excellent electroanalytical properties toward the determination of L-glutamate in a wide linear range (0.01-10 μM) with low detection limit (10 nM, S/N≥3), fast response time (≤5 s), and good operational and long-term stability. The CNT modified screen-printed electrodes have a potential to be of general interest for designing of electrochemical sensors and biosensors.     

Carbon nanotube/polysulfone composite screen-printed electrochemical enzyme biosensors

The fabrication, evaluation and attractive performance of multiwall carbon nanotube(MWCNT)/polysulfone biocomposite membrane modified thick-film screen-printed electrochemical biosensors are reported. The fabricated carbon nanotube/polysulfone (CNT/PS) strips combine the attractive advantages of carbon nanotube materials, polysulfone matrix and disposable screen-printed electrodes. Such thick-film carbon nanotubes/polysulfone sensors have a well defined performance, are mechanically stable, and exhibit high electrochemical activity. Furthermore, biocompatibility of CNT/PS composite allows easy incorporation of biological functional moiety of horseradish peroxidase by phase inversion technique. The comparison of graphite with MWCNT as conductor material is described in this paper. The proposed H(2)O(2) biosensor exhibited a linear range (applied potential, -0.2 V) from 0.02 to 0.5 mM and a K(M)(app) of 0.71 mM.     

丝网印刷电极在食品安全检测中的应用进展

食品安全问题一直以来都是被广泛关注的热点,选择成本低、使用方便、灵敏度高的检测手段也就成为了食品安全检测领域中研究的焦点。丝网印刷电极因具有可批量生产、成本低、灵敏度高和一次性可抛等特点,已被广泛应用到食品安全检测中。因此,近年来,关于丝网印刷电极在食品安全检测中的应用研究日益增多,建立了多种类型的电化学传感器。依据电化学传感器的不同类型,综述了丝网印刷电极在食品安全检测中的应用,并对丝网印刷电极的应用前景进行了展望。     

Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: A review

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.     

Electrochemical sensors based on antimony tin oxide-Prussian blue screen-printed electrode and PEDOT-Prussian blue for potassium ion detection

Journal of Solid State Electrochemistry - The development and analytical applications of electrochemical sensors based on antimony tin oxide (ATO)–Prussian blue (PB) screen-printed electrode...     

Recent developments in the field of screen-printed electrodes and their related applications

The development of analytical methods that respond to the growing need to perform rapid ‘in situ’ analyses shows disposable screen-printed electrodes (SPEs) as an alternative to the traditional electrodes. This review presents recent developments in the electrochemical application of disposable screen-printed sensors, according to the types of materials used to modify the working electrode. Therefore, unmodified SPE, film-modified SPE, enzyme-modified SPE and antigen/antibody-modified SPE are described. Applications are included where available.     

Electrochemical Determination of Methotrexate at a Disposable Screen-Printed Electrode and Its Application Studies

Methotrexate is widely used for treatment of various neoplastic diseases. The present work details the voltammetric analysis of Methotrexate at a multi-walled carbon nanotube (MWNT) modified screen-printed electrode (SPE). The fabrication and evaluation of MWNT-derived screen-printed electrochemical sensors based on a MWNT ink are reported. The fabricated MWNT strips combine the attractive advantages of CNT materials and disposable screen printed electrodes. The anodic voltammetric behavior of methotrexate was studied using cyclic and square-wave voltammetric techniques in tris-HCl (pH = 7.5) solution. The oxidation of methotrexate was an irreversible adsorptive-driven process. The experimental conditions such as carbon ink, MWNT, pH, the concentration, and nature of buffer were investigated to optimize the determination of methotrexate. Under optimum conditions, the square-wave voltammetric peak currents were in a linear relationship to methotrexate concentrations in the range of 5.0 × 10^?7M–1.0 × 10^?4 M with a detection limit of 1.0 × 10^?7 M. The MWNT/SPE showed good stability, selectivity, and was successfully used to quantify methotrexate in pharmaceutical formulations.     

Application of Carbon Nanotubes in the Extraction and Electrochemical Detection of Organophosphate Pesticides: A Review

Recent trends and challenges in developing carbon nanotubes (CNT) based sensors and biosensors for the detection of organophosphate (OP) pesticides and other organic pollutants in water are reviewed. CNT have superior electrical, mechanical, chemical, and structural properties over conventional materials such as graphite. At the same time CNT based sensors and biosensors are more efficient compared to the existing traditional techniques such as high-performance liquid chromatography or gas chromatography, because they can provide rapid, sensitive, simple, and low-cost on-field detection. The measurement protocols can be based on enzymatic and non-enzymatic detection. The enzyme acetylcholinesterase (AChE) is used with CNT for fabricating ultrasensitive biosensors for OP detection involving different immobilization schemes such as adsorption, crosslinking, and layer-by-layer self-assembly. This protocol relies on measuring the degree of enzyme inhibition as means of OP quantification. The other enzyme used along with CNT for OP detection is organophosphate hydrolase (OPH) which hydrolyzes the OP into detectable species that can be measured by amperometric or potentiometric methods. Different forms of CNT electrode materials can be used for fabricating such electrodes such as pure CNT and composite CNT. Due to their large surface area and hydrophobicity, CNT have also been used for the extraction and non-enzymatic electrochemical detection of OP with very high efficiency. The application of CNT and their novel properties for the adsorption and electrochemical detection of OP compounds is discussed in detail.     

Electrochemical Introduction of Active Sites into Super-long Carbon Nanotubes for Enhanced Capacitance

Electrochemical cyclic voltammetric(CV)scan was applied to inducing the partial oxidation and defects of carbon nanotubes(CNTs).The electrochemically induced functional groups and physical defects were...     

Electrochemical sensors and biosensors based on heterogeneous carbon materials

Abstract  

An overview of the use of electrochemical sensors made from heterogeneous carbon materials (carbon paste electrodes, screen-printed carbon electrodes) in the field of food analysis is presented. Sensors for inorganic and organic analytes as well as biosensors are summarized.     

Biosensors based on polymer networks formed by gamma irradiation crosslinking

Water-soluble polymers immobilized by gamma radiation have been investigated as a means of developing electrochemical sensors. Enzyme-based sensors for glucose and lactate have been made by immobilizing glucose oxidase and lactate oxidase, respectively, on platinized graphite electrodes. The enzyme is entrapped in a polymeric network of poly(vinyl alcohol) that is formed by gamma radiation crosslinking. Electrodes coated with poly (N-vinylpyrrolidone) and its corresponding monomer and then crosslinked with gamma radiation show an extraction of catecholamines into the polymer film that enhances the analytical signal for their detection by electrochemical oxidation. Poly(dimethyldiallylammonium chloride) spin-coated on a screen-printed electrochemical cell provides sufficient ionic conductivity for the cell to function as a gas sensor for oxygen, which is detected by reduction at a platinum working electrode.     

Carbon nanotube-modified electrodes for electrochemical DNA-sensors

Glassy-carbon electrodes (GCEs) are modified with preoxidized multiwalled carbon nanotubes (CNTs). According to the data of atomic force microscopy, the layers of CNTs on GCEs possess a homogeneous nanostructurized surface. The voltammetric properties of a GCE/CNT depend on the modifier load. Guanine and deoxyguanosine monophosphate are strongly adsorbed on GCE/CNT and oxidized at +690 and +930 mV (pH 7.0), respectively. The oxidation current of guanine DNA nucleotides adsorbed on a GCE/CNT is significantly higher for the thermally denaturated biopolymer than for the native one. Our results are of interest for the development of sensors based on the electrochemical properties of nucleic acids.     

Carbon nanotube--conducting-polymer composite nanowires

Polypyrrole/carbon nanotube (PPy/CNT) composite nanowires were prepared by a template-directed electrochemical synthetic route, involving plating of PPy into the pores of a host membrane in the presence of shortened and carboxylated CNT dopants (without added electrolyte). Cyclic voltammetric growth profiles indicate that the CNT is incorporated within the growing nanowire and serves as the sole charge-balancing "counterion". Transmission electron microscopy images indicate high-quality straight PPy/CNT nanowires with a smooth and featureless surface and a uniform diameter. The presence of the CNT dopant imparts high conductivity (Ohmic I-V behavior) onto these PPy/CNT nanowires. By combining the attractive properties of CNTs, conducting polymers, and nanowires, the new nanocomposite opens up new opportunities, ranging from chemical sensors to molecular electronic devices.     

Graphene-based Disposable Electrochemical Sensor for Chlorhexidine Determination

In this work, simple, reliable, eco-friendly, and quantitative electrochemical sensors were developed to detect chlorhexidine Digluconate (CHX) in a variety of dosage forms, including mouthwashes and intimate douches, as well as chlorhexidine in spiked human saliva. Without any sample pre-treatment or extraction processes, CHX was measured in colored aqueous formulations. Based on carbon screen-printed electrodes, two potentiometric sensors (sensors I and II), utilizing graphene nanocomposites (Gr-NC), were designed (SPEs). An ionophore, 2-hydroxypropyl-β-cyclodextrin, was doped into the Poly Vinyl Chloride (PVC) polymeric membrane to improve sensor selectivity.     

Wearable electrochemical sensors for in situ analysis in marine environments

The development of wearable screen-printed electrochemical sensors on underwater garments comprised of the synthetic rubber neoprene is reported. These wearable sensors are able to determine the presence of environmental pollutants and security threats in marine environments. Owing to its unique elastic and superhydrophobic morphology, neoprene is an attractive substrate for thick-film electrochemical sensors for aquatic environments and offers high-resolution printing with no apparent defects. The neoprene-based sensor was evaluated for the voltammetric detection of trace heavy metal contaminants and nitroaromatic explosives in seawater samples. We also describe the first example of enzyme (tyrosinase) immobilization on a wearable substrate towards the amperometric biosensing of phenolic contaminants in seawater. Furthermore, the integration of a miniaturized potentiostat directly on the underwater garment is demonstrated. The wearable sensor-potentiostat microsystem provides a visual indication and alert if the levels of harmful contaminants have exceeded a pre-defined threshold. The concept discussed here is well-suited for integration into dry- and wetsuits worn by divers and recreational surfers/swimmers, thereby providing them with the ability to continuously assess their surroundings for environmental contaminants and security hazards.     

Ratiometric Electrochemistry: Improving the Robustness,Reproducibility and Reliability of Biosensors

Electrochemical biosensors are an increasingly attractive option for the development of a novel analyte detection method, especially when integration within a point-of-use device is the overall objective. In this context, accuracy and sensitivity are not compromised when working with opaque samples as the electrical readout signal can be directly read by a device without the need for any signal transduction. However, electrochemical detection can be susceptible to substantial signal drift and increased signal error. This is most apparent when analysing complex mixtures and when using small, single-use, screen-printed electrodes. Over recent years, analytical scientists have taken inspiration from self-referencing ratiometric fluorescence methods to counteract these problems and have begun to develop ratiometric electrochemical protocols to improve sensor accuracy and reliability. This review will provide coverage of key developments in ratiometric electrochemical (bio)sensors, highlighting innovative assay design, and the experiments performed that challenge assay robustness and reliability.     

Recent trends in carbon nanomaterial-based electrochemical sensors for biomolecules: A review

Carbon nanomaterials are advantageous for electrochemical sensors because they increase the electroactive surface area, enhance electron transfer, and promote adsorption of molecules. Carbon nanotubes (CNTs) have been incorporated into electrochemical sensors for biomolecules and strategies have included the traditional dip coating and drop casting methods, direct growth of CNTs on electrodes and the use of CNT fibers and yarns made exclusively of CNTs. Recent research has also focused on utilizing many new types of carbon nanomaterials beyond CNTs. Forms of graphene are now increasingly popular for sensors including reduced graphene oxide, carbon nanohorns, graphene nanofoams, graphene nanorods, and graphene nanoflowers. In this review, we compare different carbon nanomaterial strategies for creating electrochemical sensors for biomolecules. Analytes covered include neurotransmitters and neurochemicals, such as dopamine, ascorbic acid, and serotonin; hydrogen peroxide; proteins, such as biomarkers; and DNA. The review also addresses enzyme-based electrodes that are used to detect non-electroactive species such as glucose, alcohols, and proteins. Finally, we analyze some of the future directions for the field, pointing out gaps in fundamental understanding of electron transfer to carbon nanomaterials and the need for more practical implementation of sensors.     

Electrochemical sensors and biosensors based on heterogeneous carbon materials

Abstract  An overview of the use of electrochemical sensors made from heterogeneous carbon materials (carbon paste electrodes, screen-printed carbon electrodes) in the field of food analysis is presented. Sensors for inorganic and organic analytes as well as biosensors are summarized. Graphical abstract        

Evaluation of different mediator-modified screen-printed electrodes used in a flow system as amperometric sensors for NADH

This work presents a comparative study between two different methods for the preparation of mediator-modified screen-printed electrodes, to be used as detectors in a reliable flow injection system for the determination of the nicotinamide adenine dinucleotide (NADH) coenzyme. The best strategy was selected for the final development of compact biosensors based on dehydrogenase enzymes. For the first immobilisation strategy, different redox mediators were electropolymerised onto the SPE surface. The second immobilisation strategy was carried out using polysulfone–graphite composites, which were deposited by screen-printing technology onto the screen-printed electrode (SPE) surface. Both methods achieved an effective and reliable incorporation of redox mediators to the SPE configuration. Finally, a flow system for ammonium determination was developed using a glutamate dehydrogenase (GlDH)-Meldola's Blue (MB)-polysulfone-composite film-based biosensor.

The stability of the redox mediators inside the composite films as well as the negligible fouling effect observed on the electrode surface improve the repeatability and reproducibility of the sensors, important features for continuous analysis in flow systems. Furthermore, the optimised bio/sensors, incorporated in a flow injection system, showed good sensitivities and short response times. Such a good analytical performance together with the simple and fast sensor construction are interesting characteristics to consider the polysulfone-composite films as attractive electrochemical transducer materials for the development of new dehydrogenase-based SPEs.