Electrochemical nucleic acid biosensors

Electrochemical devices have received considerable attention in the development of sequence-specific DNA hybridization biosensors. Such devices rely on the conversion of the DNA base-pair recognition event into a useful electrical signal. Electrochemical biosensing of DNA hybridization is not only uniquely qualified for meeting the size, cost, and power requirements of decentralized genetic testing, but offer an elegant route for interfacing—at the molecular level—the DNA-recognition and signal-transduction elements. This article reviews current directions in electrochemical DNA biosensors, and discusses recent strategies and future prospects for such electrical detection.     

Electrochemical biosensors for food analysis

Abstract  Food analysis has become a very important and interesting area of research because of the rapid expansion of food trade and highly increased mobility of today’s populations. Food quality control is essential both for consumer protection and also for the food industry. Application of the electrochemical biosensors in the field of food analysis is promising. This review covers the recent developments and issues in electrochemical biosensors for food analysis, such as ease of preparation, robustness, sensitivity, and realization of mass production of the detection strategies. This review also emphasizes the current development of electrochemical biosensors combined with nanotechnology. Graphical abstract        

Electrochemical biosensors for food analysis

Abstract  

Food analysis has become a very important and interesting area of research because of the rapid expansion of food trade and highly increased mobility of today’s populations. Food quality control is essential both for consumer protection and also for the food industry. Application of the electrochemical biosensors in the field of food analysis is promising. This review covers the recent developments and issues in electrochemical biosensors for food analysis, such as ease of preparation, robustness, sensitivity, and realization of mass production of the detection strategies. This review also emphasizes the current development of electrochemical biosensors combined with nanotechnology.     

Electrochemical biosensors for rapid pathogen detection

Rapid pathogen detection is an emerging issue in clinical, environmental, and food industry sectors. Biosensors can represent a solution to culture-based and molecular methods as they respond to sensitivity, specificity, and rapidity needs. Screen-printed electrodes have been used in association with nanoparticles to increase the signal and improve sensitivity reaching low numbers of the targets. Antibodies, DNA probes, and aptamers are mainly used to functionalize the working electrodes to ensure high specific pathogen detection by the use of voltammetry, impedance spectroscopy, amperometry, and conductivity. Electrochemical biosensors can be miniaturized to construct portable devices useful for in situ assays.     

Electrochemical biosensors based on horseradish peroxidase

The principles used for the development of electrochemical biosensors based on horseradish peroxidase are described. Peroxidase is the enzyme which catalyses the oxidation of a variety of organic molecules in the presence of hydrogen peroxide. The features of this enzyme are high catalytic activity and low specificity towards second substrate as well. Horseradish peroxidase may be used as a component of active part of biosensors for the detection of hydrogen peroxide and other compounds when peroxidase is co-immobilized together with other oxidases. Also horseradish peroxidase may be used as a component of detecting system for the biosensors based on biological recognition using specific antibodies, receptors, nucleic acids. The examples of the bio-, immuno-, DNA-sensors developed for the determination of various biologically active compounds are given.     

Electrochemical biosensors for monitoring the recognition of glycoprotein-lectin interactions

Despite the wide applicability and specificity of lectins to carbohydrate moieties, there are few lectin specific biosensors. This is attributed to the difficulty in defining the relevant experimental parameters to measure for sensing. We hereby describe the development of direct and indirect electrochemical sensors to determine the exact trace amounts of probarley lectin (ProBL) and its conversion product wheat germ agglutinin (WGA). In addition to WGA, the antigens (ProBL) employed in this study were over expressed in bacteria, isolated from protein bodies, and purified using immobilized N-acetylglusamine in order to obtain correctly folded active lectins. The amperometric immunosensor uses cell lines producing monoclonal antibody (mAB) to the pro-region of ProBL over expressed from Escherichia coli. The efficacy and sensing characteristics of the lectin were optimized using monoclonal antibody to WGA and the resulting sensor was found to detect only ProBL in the linear range 10⁻³-10² μg mL⁻¹ and a detection limit of 10⁻³ μg mL⁻¹.     

Electrochemical biosensors for determination of nystatin activity

Nystatin is determined by recording the current of an oxygen-based biosensor or the potential of carbon dioxide-based biosensor. The yeast strain Saccharomyces cerevisiae is immobilized on an acetylcellulose filter and fixed to the surface of the electrochemical sensor. Both biosensors monitor the death of the strain the additiin of the antigungal solution and a measurable change of the curent (or potential), and the slope of the recording at the midpoint of the sigmoidal curve can be related to the nystatin activity. The carbondioxide-based biosensor provides a larger response range (100–500 U ml⁻¹ nystatin) but the oxgen-based sensor is more sensitive (25–100 U ml⁻¹ nystatin). All analyses are done at pH 4.5 where the response times of the electrochemical sensors are similar.     

Electrochemical biosensors in nonaqueous solutions and their applications.

This review first describes the invention of functional interfaces to promote biochemical redox reactions between substrates in dipolar aprotic solvents and enzymes or related compounds immobilized at the interface. The interfaces contain hydrophilic polymer membranes, a gold nanoparticle self-assembled electrode constructed by using rigid rod dithiols, and binary self-assembled monolayers composed of amino and carboxyl terminal groups. Other topics covered are: the electrochemical characterization of the hydrophilic polymer membrane; the development of biosensors to obtain reaction parameters of enzymatic and of electrochemical kinetics; and applications to the study of materials involved in metabolism.     

Electrochemical biosensors based on enzymes immobilized in electropolymerized films

A review based on 135 references concerns the design and properties of electrochemical biosensors for 13 different substrates of enzymatic reactions. In the sensors discussed the enzymes are immobilized within or on the top of electropolymerized films, mostly of conducting polymers. Amperometric detection is most often used for internal electrochemical sensing.Dedicated to our late colleague Wojciech Matuszewski     

Electrochemical and piezoelectric DNA biosensors for hybridisation detection

DNA biosensors (or genosensors) are analytical devices that result from the integration of a sequence-specific probe and a signal transducer. Among other techniques, electrochemical and piezoelectric methods have recently emerged as the most attractive due to their simplicity, low instrumentation costs, possibility for real-time and label-free detection and generally high sensitivity.Focusing on the most recent activity of worldwide researchers, the aim of the present review is to give the readers a critical overview of some important aspects that contribute in creating successful genosensing devices. Advantages and disadvantages of different sensing materials, probe immobilisation chemistries, hybridisation conditions, transducing principles and amplification strategies will be discussed in detail. Dedicated sections will also address the issues of probe design and real samples pre-treatment. Special emphasis will be finally given to those protocols that, being implemented into an array format, are already penetrating the molecular diagnostics market.     

Electrochemical lectin based biosensors as a label-free tool in glycomics

Glycans and other saccharide moieties attached to proteins and lipids, or present on the surface of a cell, are actively involved in numerous physiological or pathological processes. Their structural flexibility (that is based on the formation of various kinds of linkages between saccharides) is making glycans superb "identity cards". In fact, glycans can form more "words" or "codes" (i.e., unique sequences) from the same number of "letters" (building blocks) than DNA or proteins. Glycans are physicochemically similar and it is not a trivial task to identify their sequence, or—even more challenging—to link a given glycan to a particular physiological or pathological process. Lectins can recognise differences in glycan compositions even in their bound state and therefore are most useful tools in the task to decipher the "glycocode". Thus, lectin-based biosensors working in a label-free mode can effectively complement the current weaponry of analytical tools in glycomics.This review gives an introduction into the area of glycomics and then focuses on the design, analytical performance, and practical utility of lectin-based electrochemical label-free biosensors for the detection of isolated glycoproteins or intact cells.

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.     

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        

Electrochemical DNA biosensors based on platinum nanoparticles combined carbon nanotubes

Platinum nanoparticles were used in combination with multi-walled carbon nanotubes (MWCNTs) for fabricating sensitivity-enhanced electrochemical DNA biosensor. Multi-walled carbon nanotubes and platinum nanoparticles were dispersed in Nafion, which were used to fabricate the modification of the glassy carbon electrode (GCE) surface. Oligonucleotides with amino groups at the 5′ end were covalently linked onto carboxylic groups of MWCNTs on the electrode. The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated daunomycin. Due to the ability of carbon nanotubes to promote electron-transfer reactions, the high catalytic activities of platinum nanoparticles for chemical reactions, the sensitivity of presented electrochemical DNA biosensors was remarkably improved. The detection limit of the method for target DNA was 1.0 × 10⁻¹¹ mol l⁻¹.     

Electrochemical nanostructured biosensors: carbon nanotubes versus conductive and semi-conductive nanoparticles

The aim of this work was to demonstrate that various types of nanostructures provide different gains in terms of sensitivity or detection limit albeit providing the same gain in terms of increased area. Commercial screen printed electrodes (SPEs) were functionalized with 100 µg of bismuth oxide nanoparticles (Bi₂O₃ NPs), 13.5 µg of gold nanoparticles (Au NPs), and 4.8 µg of multi-wall carbon nanotubes (MWCNTs) to sense hydrogen peroxide (H₂O₂). The amount of nanomaterials to deposit was calculated using specific surface area (SSA) in order to equalize the additional electroactive surface area. Cyclic voltammetry (CV) experiments revealed oxidation peaks of Bi₂O₃ NPs, Au NPs, and MWCNTs based electrodes at (790 ± 1) mV, (386 ± 1) mV, and (589 ± 1) mV, respectively, and sensitivities evaluated by chronoamperometry (CA) were (74 ± 12) µA mM^?1 cm^?2, (129 ± 15) ±A mM^?1 cm^?2, and (54 ± 2) ±A mM^?1 cm^?2, respectively. Electrodes functionalized with Au NPs showed better sensing performance and lower redox potential (oxidative peak position) compared with the other two types of nanostructured SPEs. Interestingly, the average size of the tested Au NPs was 4 nm, under the limit of 10 nm where the quantum effects are dominant. The limit of detection (LOD) was (11.1 ± 2.8) ±M, (8.0 ± 2.4) ±M, and (3.4 ± 0.1) ±M for Bi₂O₃ NPs, Au NPs, and for MWCNTs based electrodes, respectively.     

A rubidium ion-selective electrode for the assay of polyene antibiotics

The preparation of a rubidium ion-selective electrode is described. The performance characteristics of the electrode are such that it can be used as an alternative to atomic absorption spectrometry in the assay of bulk nystatin, by measuring the rubidium ion efflux from specially prepared yeast cells. The electrode simplifies assay procedures because rubidium(I) can be determined directly in cell suspensions without prior centri-fugation; assay time is reduced to 10 min. The sensitivity of the method is 2 units of antibiotic per ml, which is comparable with other physico-chemical methods of bioassay but some 10 times more sensitive than the conventional agar diffusion assay.     

A microtitre plate assay for the detection of antibiotics in porcine urine

Techniques for screening porcine samples for antimicrobial residues in the EU usually involve analysis of samples taken post slaughter, and are either time consuming or expensive. Some of the positive test results at this screening stage could be avoided by allowing the animal sufficient withdrawal time following drug treatment. A method is described that can detect the presence of five major antibiotics in porcine urine at concentrations below 1 microgram ml-1 for each of the compounds. The test uses Bacillus subtilis, which is already widely employed in antimicrobial inhibition assays, and when combined with a colorimetric substrate, p-nitrophenyl-beta-D-glucopyranoside, can detect inhibitory substances within an assay time of four and a half hours. The method, which uses microtitre plate technology, could be developed into a convenient test kit for use at farm level to determine whether animals were still excreting antimicrobials in their urine prior to their submission for slaughter.     

Electrochemical property and analysis application of biosensors in miscible nonaqueous media—Room-temperature ionic liquid

Stable heme proteins entrapped in dimethylformamide (DMF)–chitosan organohydrogel films modified electrodes were operated in neat hydrophilic room-temperature ionic liquid (IL) [bmim][BF₄] for the first time. The modified electrodes possess outstanding electrochemical response in [bmim][BF₄] without adding water. The morphology studies of films were demonstrated by atomic force microscopy (AFM). UV–Vis and FTIR spectroscopy showed that the heme proteins retained their native structure in organohydrogel films. Direct electrochemistry and bioelectrocatalysis of heme protein–organohydrogel films were investigated. Several electrochemical parameters such as the charge transfer coefficients (α) and the apparent electron transfer rate constant (k_s) of these processes were calculated by performing nonlinear regression analysis of square wave voltammetry (SWV) experimental dates. Furthermore, high electrocatalytic activity to hydrogen peroxide (H₂O₂) was observed, indicating that heme proteins entrapped in organohydrogel films retained their bioelectrocatalytic activities in [bmim][BF₄]. Kinetic analysis of the cyclic voltammetry dates shows that heme protein–organohydrogel films operated in IL bring up to an enhancement of the biosensor sensitivity and a high affinity for H₂O_2.     

The assay of antibiotics in pharmaceutical preparations using reverse-phase HPLC

Chromatographic methods are presented for the determination of chloramphenicol, erythromycin, tyrothricin, nystatin, penicillin, streptomycin, sulphanilamides and nitrofurans, in some pharmaceutical formulations. The methods have been applied in routine analysis and are in general capable of distinguishing the main antibiotic from decomposition products and likely congeners.