Oxidative grafting vs. monolayers self-assembling on gold surface for the preparation of electrochemical immunosensors. Application to the determination of peptide YY

Novel sensitive immunosensor for the selective detection of Engrailed 2 urinary prostate cancer biomarker

Engrailed 2 (EN2) is a homeodomain-containing transcription factor expressed in prostate cancer (PCa) cell lines and is secreted into the urines. It is nowadays considered as a promising non-invasive biomarker for PCa early diagnosis. Herein, we report the design of an electrochemical immunosensor for EN2 detection. The biosensor fabrication involved a covalent immobilization of anti-EN2 antibodies onto a poly para amino benzoic acid (PABA) film electropolymerized on a gold electrode. Square wave voltammetry was investigated for EN2 detection in a phosphate buffer solution in a concentration range of 10^-5 ng/mL to 1 μg/mL. The limit of detection of the designed sensor was equal to 10^-5 ng/mL and the sensitivity was of order of (29 ± 2) μL/ng. The dissociation constant K_d of the "complex" EN2/anti-EN2, estimated from a Hill model, was of order of (0.9 ± 0.2) fM. Experimental results revealed that the immunosensor enabled selective detection of EN2 in a mixture of three proteins which can be found in men' urine: human serum albumin (HSA), prostate-specific antigen (PSA) and immunoglobulin G (IgG). Tests in artificial urine, with an ionic strength of 0.18 M, have been done and results were found comparable to those obtained in PBS (0.16 M). These encouraging results show a potentially promising future for the development of an electrochemical biosensor for robust and accurate urinary biomarkers detection.

One-step enzyme-free dual electrochemical immunosensor for histidine-rich protein 2 determination

In the present work, we describe a novel one-step enzyme-free dual electrochemical immunosensor for the determination of histidine-rich protein 2 (Ag-PfHRP2), a specific malaria biomarker. A gold electrode (GE) was functionalized with the PfHRP2 antibody (Ab-PfHRP2) using dihexadecyl phosphate (DHP) polymer as an immobilization platform. The Ab-PfHRP2/DHP/GE sensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The developed immunosensor was employed for indirect Ag-PfHRP2 determination by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The linear range was 10-400 ng mL-1 and 10-500 ng mL-1 for EIS and DPV, while the limit of detection was 3.3 ng mL-1 and 2.8 ng mL-1, respectively. The electrochemical immunosensor was successfully applied for Ag-PfHRP2 determination in human serum samples. Its performance was compared with an ELISA test, and good correspondence was achieved. The coefficients of intra- and inter-assay variations were less than 5%. The electrochemical immunosensor is a useful and straightforward tool for in situ malaria biomarker determination.

Advances in immunosensor technology

In recent years, advances in immunosensor device fabrication have significantly expanded the use of this technology in a broad range of applications including clinical diagnosis, food analysis, quality control, environmental studies and industrial monitoring. The most important aspect in fabrication is to obtain a design that provides a low detection limit. The utilization of nanomaterials as a label, catalyst and biosensing transducer is, perhaps, the most popular approach in ultrasensitive devices. This chapter reviews recent advances in immunosensor fabrication and summarizes the most recent studies. Strategies employed to significantly improve sensitivity and specificity of immunosensor technology and the advantages and limitations thereof are explored.

Electrochemical Immunosensing Platform for the Determination of the 20S Proteasome Using an Aminophenylboronic/Poly-indole-6-carboxylic Acid-Modified Electrode

The first electrochemical immunosensor for the determination of the 20S proteasome (P20S) was developed, entailing the immobilization of an antibody on an aminophenylboronic/poly-indole-6-carboxylic acid-modified electrode. The proposed electrochemical bioplatform is a simple and feasible analytical tool applicable for the determination of P20S in human plasma, considering its high clinical and biological relevance. Cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry (SWV) were used to determine the optimal step-by-step process to obtain the electrochemical immunosensor. The interaction of P20S with the recognition layer of the immobilized antibody on the nanostructured surface took place by incubating the electrode in a P20S solution at 20 °C for 2 h. Using SWV as an electro-analytical technique, this immunosensor can quantify P20S. The current was linear with the P20S concentration within two dynamic concentration ranges from 20.0 to 80.0 and 80.0 to 200.0 ng·mL^-1 (r² = 0.992 and 0.98, respectively) with a limit of detection and quantification of 6 and 18 ng·mL^-1, respectively. Moreover, the immunosensor showed considerable repeatability and reproducibility, when the determination was done in human serum, which confirms that it is a promising alternative for direct detection of P20S in biological fluids with minimal interference.

Electrochemical Immunosensors for Antibiotic Detection

Antibiotics are an important class of drugs destined for treatment of bacterial diseases. Misuses and overuses of antibiotics observed over the last decade have led to global problems of bacterial resistance against antibiotics (ABR). One of the crucial actions taken towards limiting the spread of antibiotics and controlling this dangerous phenomenon is the sensitive and accurate determination of antibiotics residues in body fluids, food products, and animals, as well as monitoring their presence in the environment. Immunosensors, a group of biosensors, can be considered an attractive tool because of their simplicity, rapid action, low-cost analysis, and especially, the unique selectivity arising from harnessing the antigen-antibody interaction that is the basis of immunosensor functioning. Herein, we present the recent achievements in the field of electrochemical immunosensors designed to determination of antibiotics.