Adsorption: an easy and efficient immobilisation of acetylcholinesterase on screen-printed electrodes

An amperometric biosensor based on acetylcholinesterase was constructed by simple adsorption of the enzyme on screen-printed electrodes (SPEs). This sensor was used to detect the inhibitory effects of organophosphorus and carbamate insecticides on acetylcholinesterase, and more particularly of chlorpyrifos ethyl oxon (CP-o). We demonstrate that enzyme adsorption on SPEs allows to obtain stable sensors that present good characteristics and are as efficient as other screen-printed biosensors based on covalent binding or entrapment of acetylcholinesterase (AChE).     

Screen-printed biosensors in microbiology; a review

Disposable screen-printed biosensors have been successfully employed in the development of analytical methods that respond to the growing need to perform rapid “in situ” analyses. Thus, the early detection of microorganisms, which plays an important role in the prevention of human health problems, animals and plants epidemics, has been carried out using this kind of devices. Moreover, microorganisms have been used as biological sensing elements in the development of sensitive microbial biosensors for the analysis of different analytes of interest. This review presents the electrochemical application of disposable screen-printed biosensors in the microbiology field.     

Layer-by-layer electrodeposition of redox polymers and enzymes on screen-printed carbon electrodes for the preparation of reagentless biosensors

Layer-by-layer electrodeposition of redox polymer/enzyme composition films on screen-printed carbon electrodes for fabrication of reagentless enzyme biosensors has been proposed and the resulting films were found to be very stable and rigid.     

Screen-printed biosensors for the control of wine quality based on lactate and acetaldehyde determination

Biosensors for d-lactate and acetaldehyde were developed, based on screen-printed electrodes and NAD⁺-dependent dehydrogenases. Modification of screen-printed electrodes with the mediator Meldola Blue or with Meldola Blue-Reinecke salt resulted in sensitive, low cost and reliable NADH detectors. The biosensors were realised in two configurations, as disposable and reusable devices. Single-use sensors were obtained by simple deposition of enzyme and cofactor on the surface of mediator-modified electrodes. Chronoamperometry was used for the detection of substrates in small volumes of samples (25 μl). Immobilisation of dehydrogenases by entrapment in poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) allowed sensors to be obtained with sufficient operational stability. Amperometry in stirred solutions was the detection technique with biosensors for multiple use. The 3σ detection limits for acetaldehyde were 1 μM by amperometry and 6 μM by chronoamperometry and for d-lactate-0.03 μM and 0.05 μM for reusable and disposable biosensors respectively. The biosensors were applied in the analysis of some French and Romanian wines.     

CYP450 biosensors based on screen-printed carbon electrodes for the determination of cocaine

A new electrochemical method has been described and characterized for the determination of cocaine using screen-printed biosensors. The enzyme cytochrome P450 was covalently attached to screen-printed carbon electrodes. Experimental design methodology has been performed to optimize the pH and the applied potential, both variables that have an influence on the chronoamperometric determination of the drug. This method showed a reproducibility of 3.56% (n = 4) related to the slopes of the calibration curves performed in the range from 19 up to 166 nM. It has been probed the used of this kind of biosensors in the determination of cocaine in street samples, with an average capability of detection of 23.05 ± 3.53 nM (n = 3, α = β = 0.05).     

Electrochemical Investigation of Gold Based Screen Printed Electrodes: An Application for a Seafood Toxin Detection

Although commercial screen-printed electrodes (SPEs) are used extensively for biosensor purposes nowadays, detailed studies on characterization are still limited. In this study, the surface of the gold-based screen-printed electrode (SPGE) was carefully modified with self-assembly-monolayer through an optimized immobilization procedure. The key physical and chemical properties with regeneration capacity of the developed biosensors were assessed by various characterization techniques. Then SPGE was used to determine its sensitivity, limit of detection (LOD) and limit of quantification (LOQ) for a toxin substance of domoic acid in seafood that has become more common and rising concern of marine wildlife and seawater pollution. LOD in phosphate buffered saline (PBS) and cell culture media were obtained as 2.93 ng mL⁻¹ and 4.28 ng mL⁻¹, respectively. The reduced sensitivity for antibody-based biosensors in the cell culture medium was probably due to interaction of nonspecific compounds with DA in the culture medium compared to the much less complex environment of PBS. In addition, the regeneration capacity has been found very limited due to inherent heterogeneity and low robustness. This study can be used for the main challenges with the design requirements of commercial SPE-based biosensors to provide a detailed perspective for further toxicity studies.     

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.     

A disposable, screen-printed electrode for the amperometric determination of azide based on the immobilization with catalase or tyrosinase.

A disposable, screen-printed electrode based on the immobilization of catalase or tyrosinase was developed to construct biosensors for the amperometric determination of azide. The determination principles for azide by these two methods are based on inhibiting the enzymatic consumption of an electrode-detectable substance (hydrogen peroxide or catechol) on an enzyme-immobilized electrode. Both of these methods show a sensitive detection range and a short measuring time.     

Determination of Residual Pesticide in Plant Materials Using Planar Cholinesterase Sensors Modified with Nafion

Amperometric cholinesterase biosensors based on planar screen-printed carbon electrodes modified with Nafion were developed for determining residual pesticides exhibiting anticholinesterase activity in plant materials. When stored under dry conditions, biosensors retained their normal operation for six months. Simplified extraction methods were proposed to eliminate the effects of the matrix and organic solvents. The developed procedure provides the direct determination of down to 0.1 mg/kg pesticides in wheat, barley, sorghum, and rice grains without the removal of organic solvents.     

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.     

Application of screen-printed microband biosensors incorporated with cells to monitor metabolic effects of potential environmental toxins

Microband biosensors were fabricated from a screen-printed water-based carbon ink containing cobalt phthalocyanine redox mediator and glucose oxidase or lactate oxidase enzyme. The microbiosensors were characterised for their ability to monitor ferrocyanide and H₂O₂ in phosphate buffer solution: sigmoidal cyclic voltammograms, high current density values and steady-state amperometric responses confirmed the existence of radial-diffusion-limiting microelectrode behaviour. The lactate microband biosensors were then used, in conjunction with a screen-printed Ag/AgCl reference and platinum counter electrode, to monitor lactate levels in culture medium, with a linear range of 0.5–5 mM, sensitivity of 20 nA.mM^?1, and dynamic range up to >9 mM. The lactate microband biosensors could operate continuously in culture medium over extended times (up to 24 h) at 37 °C. These biosensors were then applied to detect changes in lactate release from cultured cells in response to toxic challenge: m-dinitrobenzene (500 μM) caused a reduction in lactate production by high-passage number HepG2 single cells; D-galactosamine (20 mM) induced release of lactate by HepG2 spheroid cultures. This novel use of microband biosensors in cell culture has the potential for further application in toxicity monitoring, in both environmental and pharmaceutical areas.     

Biosensors as new analytical tool for detection of Genetically Modified Organisms (GMOs)

Three different biosensors for detection of Genetically Modified Organisms (GMOs) are presented. The sensing principle is based on the affinity interaction between nucleic acids: the probe is immobilised on the sensor surface and the target analyte is free in solution. The immobilised probes are specific for most inserted sequences in GMOs: the promoter P35S and the terminator TNOS. Electrochemical methods with screen-printed electrodes, piezoelectric and optical (SPR) transduction principles were applied.     

Biosensors as new analytical tool for detection of Genetically Modified Organisms (GMOs)

Three different biosensors for detection of Genetically Modified Organisms (GMOs) are presented. The sensing principle is based on the affinity interaction between nucleic acids: the probe is immobilised on the sensor surface and the target analyte is free in solution. The immobilised probes are specific for most inserted sequences in GMOs: the promoter P35S and the terminator TNOS. Electrochemical methods with screen-printed electrodes, piezoelectric and optical (SPR) transduction principles were applied.     

Determination of phenolic acids using Trametes versicolor laccase

Two biosensors based on Trametes versicolor laccase (TvL) were developed for the determination of phenolic compounds. Commercial oxygen electrode and ferrocene-modified screen-printed graphite electrodes were used for preparation of laccase biosensors. The systems were calibrated for three phenolic acids. Linearity was obtained in the concentration range 0.1-1.0 μM caffeic acid, 0.05-0.2 μM ferulic acid, 2.0-14.0 μM syringic acid for laccase immobilised on a commercial oxygen electrode and 2.0-30.0 μM caffeic acid, 2.0-10.0 μM ferulic acid, 4.0-30.0 μM syringic acid for laccase immobilised on ferrocene-modified screen-printed electrodes. Furthermore, optimal pH, temperature and thermal stability studies were performed with the commercial oxygen electrode. Both electrodes were used for determination of a class of phenolic acids, achieving a cheap and fast tool and an easy to be used procedure for screening real samples of human plasma.     

Application of cell-based biosensors for the detection of bacterial elicitor flagellin

Cell-based biosensors, bioelectronic portable devices containing plant living cells have been used for monitoring some physiological changes induced by pathogen-derived signal molecules called flagellin. The screen-printed electrodes have been adapted for preparation of biosensors. The proton-sensitive thick films have been printed using composite bulk modified with edition of RuO(2). Obtained disposable electrodes were made possible to measure the pH change with well sensitivity and reproducibility. Tobacco cells attached to the electrode surface, cell-based biosensor, can be used for the detection of flagellin, the virulence factor of bacterial pathogen. We culture tobacco cells on the surface of such electrotransducer for several weeks and monitor of potential of cells under flagellin stimulation. The detection of the electrochemical proton gradient across the plasma membrane serves as the analytical signal. The electrode response depended upon H(+) concentration in extracellular solution. It can be conveniently observed on the surfaces of biosensors. Suitable stability and the good response time of constructed biosensors were observed. Future development of these cell-based biosensors could draw advances in selective monitoring of microbial pathogens and other physiologically active components. Moreover, this new method is much faster compared with the traditional microbial testing.     

Detection of carbamic and organophosphorous pesticides in water samples using a cholinesterase biosensor based on Prussian Blue-modified screen-printed electrode

In the present paper, a comparative study using Co-phthalocyanine and Prussian Blue-modified screen-printed electrodes, has been performed. Both the electrodes have demonstrated an easiness of preparation together with high sensitivity towards thicoholine (LOD = 5 × 10⁻⁷ and 5 × 10⁻⁶ M for Co-phthalocyanine and Prussian Blue, respectively) with high potentialities for pesticide measurement. Prussian Blue-modified screen-printed electrodes were then selected for successive enzyme immobilization due to their higher operative stability demonstrated in previous works. AChE and BChE enzymes were used and inhibition effect of different pesticides was studied with both the enzymes. AChE-based biosensors have demonstrated a higher sensitivity towards aldicarb (50% inhibition with 50 ppb) and carbaryl (50% inhibition with 85 ppb) while BChE biosensors have shown a higher affinity towards paraoxon (50% inhibition with 4 ppb) and chlorpyrifos-methyl oxon (50% inhibition with 1 ppb). Real samples were also tested in order to evaluate the matrix effect and recovery values comprised between 79 and 123% were obtained.     

Disposable biosensors for determination of biogenic amines

This work reports monoamine oxidase (MAO)/horseradish peroxidase (HRP) and diamine oxidase (DAO)/horseradish peroxidase (HRP) based biosensors using screen-printed carbon electrodes for the determination of biogenic amines (BA). The enzymes have been covalently immobilized onto the carbon working electrode, previously modified by an aryl diazonium salt, using hydroxysuccinimide and carbodiimide. The detection has been performed by measuring the cathodic current due to the reduction of the mediator hydroxymethylferrocene at a low potential, 250 mV vs screen-printed Ag/AgCl reference electrode. The experimental conditions for the enzymes immobilization, as well as for the main variables that can influence the chronoamperometric current have been optimized by the experimental design methodology. Under these optimum conditions, the disposable biosensors have been characterized. A linear response range from 0.2 up to 1.6 μM and from 0.4 to 2.4 μM of histamine was obtained for DAO/HRP and MAO/HRP based biosensors, respectively. The biosensor construction was highly reproducible, yielding relative standard deviations of 10% and 11% in terms of sensitivity for DAO/HRP and MAO/HRP based biosensors, respectively. The capability of detection, 0.18 ± 0.01 μM in the case of DAO/HRP and 0.40 ± 0.04 μM (α = 0.05 and β = 0.005) for MAO/HRP based biosensors, and the biosensor sensitivity towards different BA has also been analyzed. Finally, the developed biosensors have been applied to the determination of the total amine content in fish samples.     

Cyclodextrin-modified biosensors: comparision of cyclodextrin-linked ferrocenes as mediators in sol-gel and screen-printed formats for sensing acetylcholine.

This work reports the comparison of a sol-gel and a screen-printed biosensor format using new mediators and a sensitive thin-film (ref. 1: P. Kataky and D. Parker, Analyst, 1996, 121, 1829) to enhance the sensitivity and stability of biosensors. The new mediators were per-alkylated cyclodextrin linked ferrocenes and a control, ferrocene aminocarboxylic acid. The thin film comprised a cocktail with polyurethane, plasticiser, lipophilic anion and a perethylated beta-CD. The analyte targeted was acetylcholine using the established horseradish peroxidase-choline-oxidase-acetylcholine esterase relay. The screen-printed electrode format showed a marked decrease in oxidation potential, the magnitude of the shift depended on the structure of the mediator and the membrane covering. Although lower oxidation-potentials were observed with the sol-gel format sensors, their response was more akin to aqueous solution behaviour. Electrocatalytic currents were observed suggesting a highly efficient electron transfer process.     

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.     

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