Amperometric biosensor based on a site-specific immobilization of acetylcholinesterase via affinity bonds on a nanostructured polymer membrane with integrated multiwall carbon nanotubes

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol A

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 μg CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD-IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD-IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 × 10^-8 - 3.6 × 10^-6 M with a detection limit of 1.1 × 10^-8 M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD-IL/SPCE were 2.0 × 10^-8 - 4.0 × 10^-6 M and 6.2 × 10^-9 M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.

Development of enzymatic electrochemical biosensors for organophosphorus pesticide detection

The enzymatic electrochemical biosensor has the advantages of simple operation, speed, and integration in the detection of organophosphorus pesticide (OPs) residues. It has the potential to become the best alternative to the traditional OP detection technology. This article introduces the OP identification principle of different enzymes, the OP detection mechanism of several common sensors, and the enzyme assembly method. In addition, the article discusses application of nanomaterials in sensor preparation and sensor performance parameters in the past decade. The related content of early sensors is outside the scope of this article.

Design and Development of Acetylthiocholine Electrochemical Biosensor Based on Zinc Oxide-Cerium Oxide Nanohybrid Modified Platinum Electrode

Acetylcholinesterase (AChE) enzyme has been predominantly used for the detection of pesticides and metal ions. But, these sensors respond to pesticides as well as metal ions at certain concentration, which results in poor selectivity. Hence in this work, the amount of thiocholine produced during AChE inhibition has been estimated to detect the residual activity of AChE enzyme in-turn to enhance the efficiency of the biosensor. In this context, Pt/ZnO-CeO₂/AChE/Chitosan based biosensor has been developed for sensitive voltammetric quantification of thiocholine in AChE. The sensor exhibited enhanced electron transfer rate, good conductivity and biocompatibility. Both the intrinsic and extrinsic parameters were simultaneously optimized using second order polynomial regression to get the best conditions for ATCh determination. Under optimized experimental conditions, the redox peak current was linear over the concentration range of 0.1-1.5 mM with detection and quantification limit of 0.05 and 0.15 μM respectively and the sensitivity of 1.47 μA mM^-1.

Nanomaterials-based enzyme electrochemical biosensors operating through inhibition for biosensing applications

In recent years great progress has been made in applying nanomaterials to design novel biosensors. Use of nanomaterials offers to biosensing platforms exceptional optical, electronic and magnetic properties. Nanomaterials can increase the surface of the transducing area of the sensors that in turn bring an increase in catalytic behaviors. They have large surface-to-volume ratio, controlled morphology and structure that also favor miniaturization, an interesting advantage when the sample volume is a critical issue. Biosensors have great potential for achieving detect-to-protect devices: devices that can be used in detections of pollutants and other treating compounds/analytes (drugs) protecting citizens' life. After a long term focused scientific and financial efforts/supports biosensors are expected now to fulfill their promise such as being able to perform sampling and analysis of complex samples with interest for clinical or environment fields. Among all types of biosensors, enzymatic biosensors, the most explored biosensing devices, have an interesting property, the inherent inhibition phenomena given the enzyme-substrate complex formation. The exploration of such phenomena is making remarkably important their application as research and applied tools in diagnostics. Different inhibition biosensor systems based on nanomaterials modification has been proposed and applied. The role of nanomaterials in inhibition-based biosensors for the analyses of different groups of drugs as well as contaminants such as pesticides, phenolic compounds and others, are discussed in this review. This deep analysis of inhibition-based biosensors that employ nanomaterials will serve researchers as a guideline for further improvements and approaching of these devices to real sample applications so as to reach society needs and such biosensor market demands.

Improvement of an antibody-enzyme coupling yield by enzyme surface supercharging

Background

Protein cross-coupling reactions demand high yields, especially if the products are intended for bioanalytics, like enzyme-linked immunosorbent assays. Amongst other factors, the coupling yield depends on the concentration of the proteins being used for coupling. Protein supercharging of enzymes can increase the solubility dramatically, which could promote enzyme-antibody coupling reactions. A highly soluble, supercharged variant of the enzyme human enteropeptidase light chain was created by a site-directed mutagenesis of surface amino acids, used for the production of an antibody-enzyme conjugate and compared to the wild type enzyme.

Results

Wild type and mutant enzyme could successfully be cross-coupled to an antibody to give antibody-enzyme conjugates suitable for ELISA. Their assay performances and the analysis of the enzyme activities in solution demonstrate that the supercharged version could be coupled to a higher extent, which resulted in better assay sensitivities. The generated conjugate, based on the supercharged enzyme, was feasible as a reporter molecule in a sandwich ELISA and allowed the detection of epidermal growth factor with a detection limit of 15.63 pg (25 pmol/L).

Conclusion

The highly soluble, surface supercharged, human enteropeptidase light chain mutant provided better yields in coupling the enzyme to an antibody than the wild type. This is most likely related to the higher protein concentration during the coupling. The data suggest that supercharging can be applied favourably to other proteins which have to be covalently linked to other polymers or surfaces with high yields without losses in enzyme activity or specificity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-014-0088-6) contains supplementary material, which is available to authorized users.

Acetylcholinesterase biosensors for electrochemical detection of organophosphorus compounds: a review

The exponentially growing population, with limited resources, has exerted an intense pressure on the agriculture sector. In order to achieve high productivity the use of pesticide has increased up to many folds. These pesticides contain organophosphorus (OP) toxic compounds which interfere with the proper functioning of enzyme acetylcholinesterase (AChE) and finally affect the central nervous system (CNS). So, there is a need for routine, continuous, on spot detection of OP compounds which are the main limitations associated with conventional analytical methods. AChE based enzymatic biosensors have been reported by researchers as the most promising tool for analysis of pesticide level to control toxicity and for environment conservation. The present review summarises AChE based biosensors by discussing their characteristic features in terms of fabrication, detection limit, linearity range, time of incubation, and storage stability. Use of nanoparticles in recently reported fabrication strategies has improved the efficiency of biosensors to a great extent making them more reliable and robust.

Acetylcholinesterase inhibition-based biosensors for pesticide determination: a review

Pesticides released intentionally into the environment and through various processes contaminate the environment. Although pesticides are associated with many health hazards, there is a lack of monitoring of these contaminants. Traditional chromatographic methods-high-performance liquid chromatography, capillary electrophoresis, and mass spectrometry-are effective for the analysis of pesticides in the environment but have certain limitations such as complexity, time-consuming sample preparation, and the requirement of expensive apparatus and trained persons to operate. Over the past decades, acetylcholinesterase (AChE) inhibition-based biosensors have emerged as simple, rapid, and ultra-sensitive tools for pesticide analysis in environmental monitoring, food safety, and quality control. These biosensors have the potential to complement or replace the classical analytical methods by simplifying or eliminating sample preparation and making field-testing easier and faster with significant decrease in cost per analysis. This article reviews the recent developments in AChE inhibition-based biosensors, which include various immobilization methods, different strategies for biosensor construction, the advantages and roles of various matrices used, analytical performance, and application methods for constructing AChE biosensors. These AChE biosensors exhibited detection limits and linearity in the ranges of 1.0×10(-11) to 42.19 μM (detection limits) and 1.0×10(-11)-1.0×10(-2) to 74.5-9.9×10(3)μM (linearity). These biosensors were stable for a period of 2 to 120days. The future prospects for the development of better AChE biosensing systems are also discussed.