Immunosensors

The condensation of 1,1′-ferrocenedimethanol and lipoic acid yields a ferrocene derivative (FcD): 1,1′-ferrocenyl bis(methylene lipoic acid ester), a bipodant linker which was used to aggregate gold nanoparticles (AuNPs). The FcD/AuNP aggregations displayed a very well-resolved signal related to the ferrocene oxidation to ferrocenium. The aggregates were found to form an efficient transducing system for a novel concept of immunosensing based on the shifting of the ferrocene oxidation potential. αHIgG/FcD/AuNP or chicken αGIgG/FcD/AuNP bioconjugates are used along with carbon SPEs as an immunosensing platform for the detection of HIgG or GIgG as model analytes. As shown by CV and DPV, the antigens addition triggers significant anodic potential shifts (up to 75 mV) of the ferrocene oxidation peak as an immunoresponse for the Ag–Ab recognition. The results from selectivity and specificity experiments using bovine serum albumin, ovalbumin and α-lactalbumin as potentially interfering proteins to HIgG Ag showed that these potential shifts would be solely due to the Ag–Ab recognition events with excellent selectivity and specificity in the presence of up to 1000-fold of the competitive proteins.

Demanded by modern medical diagnosis, advances in microfabrication technology have led to the development of fast, sensitive and selective electrochemical sensors for clinic analysis. This review addresses the principles behind electrochemical sensor design and fabrication, and introduces recent progress in the application of electrochemical sensors to analysis of clinical chemicals such as blood gases, electrolytes, metabolites, DNA and antibodies, including basic and applied research. Miniaturized commercial electrochemical biosensors will form the basis of inexpensive and easy to use devices for acquiring chemical information to bring sophisticated analytical capabilities to the non-specialist and general public alike in the future.

Nanotechnology is one of the key fields for electrochemical, optical, and mass sensitive biosensors. The nanomaterials are used as an efficient catalytic tool for electron transfer, immobilization platforms as well as electroactive and optical labels to improve the biosensing performance in terms of high sensitivity, specificity and stability. Nanomaterials or nanoparticles such as carbon nanotubes, metal nanoparticles (Au, Pt, and Pd etc.), nanowires, quantum dots and hybrid nanocomposites are playing a crucial role during the design and development of various biosensing systems for the foodborne pathogen detection. We will discuss throughout this review on the bacterial pathogens associated with foodborne illness such as toxin-producing Escherichia coli, Staphylococcal enterotoxin B, Botulinum toxins, Salmonella species, Vibrio cholerae, etc.We will also focus on electrochemical (amperometry, impedance, voltammetry), optical (surface plasmon resonance and fluorescence approach) and mass sensitive (quartz crystal microbalance, microcantilever) biosensing techniques for the detection and characterization of foodborne pathogens. In addition, recent advances in the biosensor development based on various bio-probes such as enzymes, nucleic acids, antibodies, aptamers and phage-display peptides shall be discussed. Herein, next-generation approaches explored for the multiplexed detection of food borne pathogens shall also be enlightened.

Vitreous coatings can be used as a means for the corrosion protection of metals and alloys due to their excellent dielectric properties. Their use is of particular interest in the case of highly aggressive media (different pH levels, temperatures up to 600 °C). However, ceramic coatings exposed to aggressive agents and thermal cycles can experience devitrification and spalling problems, with the consequent loss of their protective properties.The present study uses the electrochemical impedance spectroscopy technique to characterize, in a non-destructive way, the appearance of surface defects induced by the effect of temperature and chemical attack on a vitreous enamel deposited on steel. By means of analysis of the impedance diagrams obtained, a relationship is established between the loss of the coating's protective properties and the mechanism by which the corrosion process takes place.

Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and
Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin
contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as
responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in
food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for
detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer
chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent
assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quantifying aflatoxins
in foods. Each of these methods has advantages and limitations in aflatoxins analysis.This review critically examines each of the
methods used for detection of aflatoxins in foodstuff, highlighting the advantages and limitations of each method. Finally, a way
forward for overcoming such obstacles is suggested.

Clostridium difficile is worldwide most common cause of health care associated diarrhea in children and infants and is considered significant morbidity and mortality. Little is known about it epidemiology in resource limited settings. The current study was conducted at The Children’s Hospital and The Institute of Child Health, Lahore from July 2017 to December 2017 to determine the frequency of Clostridium difficile infection in paediatric patients. A total number of 61 samples were selected for this study and subsequently collected from four different wards of the hospital and processed for routine microbiological analysis. The presence of toxin was identified by specific kit using Xpect kit for C.difficile toxin. From the total of 61 samples selected, 34 (55.7%) samples belong to male patients and 27 (44.3%) samples belong to female patients. Frequency of the reactive samples came up to be 3 (4.9%) and that of the non-reactive were 58 (95.1%). Although samples were taken from four different wards but most importantly 31 (50.8%) samples were taken from Gastroenterology ward, out of which 3 (4.9%) were reactive for C. difficile toxin and remaining 28 (45.9%) were non reactive. Our results demonstrated a significant occurrence of C. difficile infection in this hospital population. There is a need to further evaluate the role of C. difficile in causing antibiotic associated diarrhea.

Pesticides, due to their intensive use and their peculiar chemical features, can persist in the environment and enter the trophic chain, thus representing an environmental risk for the ecosystems and human health. Although there are several robust and reliable standard analytical techniques for their monitoring, the high frequency of contamination caused by pesticides requires methods for massive monitoring campaigns that are capable of rapidly detecting these compounds in many samples of different origin. Immunosensors represent a potential tool for simple, rapid, and sensitive monitoring of pesticides. Antibodies coupled to electrochemical or optical transducers have resulted in effective detection devices. In this review, the new trends in immunosensor development and the application of immunosensors for the detection of pesticides of environmental concern-such as glyphosate, organophosphates, and neonicotinoids-are described.

An immunoassay in optimised conditions with a highly sensitive surface plasmon resonance (SPR) based biosensor was developed for the detection of the cancer biomarker carcinoembryonic antigen (CEA). Different formats of the immunoassay were initially investigated on the surface of the gold sensor chip. A self-assembled monolayer (SAM) was formed on the gold chip using 11-mercaptoundecanoic acid (MUDA), before the immobilisation of the antibodies was conducted. The assay was then formed in a direct capture and a sandwich assay. In order to increase the sensor signal the CEA antigen was incubated with the detection/capture antibody before it was injected to the sensor chip surface and the results were recorded in real-time using the Biacore 3000 instrument. A detection limit of 3 ng ml −1 CEA was obtained with a dynamic detection range from 3 ng ml −1 to 400 ng ml −1 with correlation coefficients of 1.00 and 0.99 for the sandwich and rabbit anti-mouse (RAM) capture assay. Kinetic data analysis was performed for the standard capture test and subsequently for the developed assays and R max showed an increase from 215 RU for the standard capture test to 428 RU for the RAM-capture assay and 734 RU for the sandwich assay, respectively. The developed SPR immunosensor using the sandwich assay format showed high sensitivity and reproducibility for CEA detection which makes it a promising procedure for cancer biomarker analysis.

In this work, a cost-effective and simple-to-prepare label-free electrochemical immunosensor was, for the first time, fabricated by modifying high-quality graphene oxide (GPO) onto a screen-printed carbon electrode (SPCE). The anti-IgG antibody was then covalently immobilized to the carboxylic group anchoring on the surface of GPO particles. Under the optimized condition, our newly developed immunosensor selectively bound to human immunoglobulin G (IgG), a model biomarker, with high sensitivity at a limit of detection of 1.99 ng mL -1 , potentially sensitive enough for IgG detection at the pathophysiological level, and had a linear range of 2.5 to 100 ng mL -1 . The proposed immunosensor also exhibited high reproducibility and regenerability, resulting in no significant change in electrochemical signals from different replicates of the electrode, and a robust electrochemical current after being subjected to alkaline base washing with several cycles. To this end, our immunosensor demonstrates ability as a promising diagnostic tool for clinical assessment.

Preparation and basic characterization of polypyrrole-based molecularly imprinted polymer (MIP) for label-free detection of bovine leukemia virus (BLV) glycoprotein gp51 (gp51) is firstly described. Polypyrrole (Ppy) was selected as a matrix for preparation of MIP. Polypyrrole doped by gp51 (gp51/Ppy) was prepared by electrochemical deposition of this polymer on the surface of platinum-black electrode. Then, molecules of gp51 were removed from polymeric backbone and molecularly imprinted polypyrrole (mPpy) was ready for recognition of gp51 in the aqueous solution. Pulsed amperometric detection (PAD) was applied for label-free detection of gp51 in the samples. Anti-gp51 antibodies and secondary antibodies labeled with horseradish peroxidase (HRP) were involved as markers for the control of mPpy preparation procedures. Control experiments were also simultaneously performed by spectrophotometrical detection of HRP activity. Application of anti-gp51 and HRP labelled secondary antibodies confirmed that generation of analytical signal was based on redoping of mPpy by gp51. During our experiments, only few mPpy redoping/dedoping cycles were effective, but generally this method seems to be very effective for the future development of mPpy-based MIPs. Preparation, electrochemical investigation and control procedures are described in the current paper.

Immunosensors are affinity ligand-based biosensor solid-state devices in which the immunochemical reaction is coupled to a transducer. The fundamental basis of all immunosensors is the specificity of the molecular recognition of antigens by antibodies to form a stable complex. This is similar to the immunoassay methodology.Immunosensors can be categorized based on the detection principle applied. The main developments are electrochemical, optical, and microgravimetric immunosensors. In contrast to immunoassay, modern transducer technology enables the label-free detection and quantification of the immune complex. The analysis of trace substances in environmental science, pharmaceutical and food industries is a challenge since many of these applications demand a continuous monitoring mode. The use of immunosensors in these applications is most appropriate. Food chemists should take advantage of immunosensors in food and clinical diagnostics. There are many recent developments in the i...

The enzyme-linked Immunosorbent Assay (ELISA) is the gold standard clinical diagnostic tool for the detection and quantification of protein biomarkers. However, conventional ELISA tests have drawbacks in their requirement of time, expensive equipment and expertise for operation. Hence, for the purpose of rapid, high throughput screening and point-of-care diagnosis, researchers are miniaturizing sandwich ELISA procedures on Lab-on-a-Chip and Lab-on-Compact Disc (LOCD) platforms. This paper presents a novel integrated device to detect and interpret the ELISA test results on a LOCD platform. The system applies absorption spectrophotometry to measure the absorbance (optical density) of the sample using a monochromatic light source and optical sensor. The device performs automated analysis of the results and presents absorbance values and diagnostic test results via a graphical display or via Bluetooth to a smartphone platform which also acts as controller of the device. The efficacy of the device was evaluated by performing dengue antibody IgG ELISA on 64 hospitalized patients suspected of dengue. The results demonstrate high accuracy of the device, with 95% sensitivity and 100% specificity in detection when compared with gold standard commercial ELISA microplate readers. This sensor platform represents a significant step towards establishing ELISA as a rapid, inexpensive and automatic testing method for the purpose of point-of-care-testing (POCT) in resource-limited settings.

Link to Full-Text Articles :
http://www.mdpi.com/1424-8220/15/5/11431/pdf 
http://www.ncbi.nlm.nih.gov/pubmed/25993517 
http://europepmc.org/abstract/med/25993517

Fast and sensitive determination of biologically active compounds is very important in biomedical diagnostics, the food and beverage industry, and environmental analysis. In this review, the most promising directions in analytical application of conducting polymers (CPs) are outlined. Up to now polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene) are the most frequently used CPs in the design of sensors and biosensors; therefore, in this review, main attention is paid to these conducting polymers. The most popular polymerization methods applied for the formation of conducting polymer layers are discussed. The applicability of polypyrrole-based functional layers in the design of electrochemical biosensors and biofuel cells is highlighted. Some signal transduction mechanisms in CP-based sensors and biosensors are discussed. Biocom-patibility-related aspects of some conducting polymers are overviewed and some insights into the application of CP-based coatings for the design of implantable sensors and biofuel cells are addressed. New trends and perspectives in the development of sensors based on CPs and their composites with other materials are discussed.

La or Pr substituted barium hexaferrites, Ba1−x(La or Pr)xFe12O19, x=0.00–0.20, were successfully prepared by a citrate combustion process. The sintered bodies were structurally and magnetically studied by powder X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). All XRD patterns show the single phase of the magnetoplumbite barium ferrite without other intermediate phases. Magnetization (MS) and coercive field (HC) could be improved by substitutions of La or Pr ions on Ba ion basis sites. The MS reveal magnetic behavior with respect to La or Pr ions content, showing an increase at first and then a decrease. The HC increases remarkably with increasing La or Pr ions content.

A Love Wave (LW) immunosensor was developed for the detection of carbaryl pesticide. The experimental setup consisted on: a compact electronic characterization circuit based on phase and amplitude detection at constant frequency; an automated flow injection system; a thermal control unit; a custom-made flow-through cell; and Quartz /SiO 2 LW sensors with a 40 μm wavelength and 120 MHz center frequency. The carbaryl detection was based on a competitive immunoassay format using LIB-CNH45 monoclonal antibody (MAb). Bovine Serum Albumin-CNH (BSA-CNH) carbaryl hapten-conjugate was covalently immobilized, via mercaptohexadecanoic acid self-assembled monolayer (SAM), onto the gold sensing area of the LW sensors. This immobilization allowed the reusability of the sensor for at least 70 assays without significant signal losses. The LW immunosensor showed a limit of detection (LOD) of 0.09 μg/L, a sensitivity of 0.31 μg/L

This review focuses on the use of conducting polymer (CP) films in electrochemical affinity sensors and emphasizes innovative designs and unique applications of immunosensors. The review covers some aspects in the application of polypyrrole (Ppy) for the creation of immunosensors. Polypyrrole film fabrication methods like solvent casting, adsorption, and electropolymerization are presented. The focus, is on electrochemically synthesized Ppy as very promising material for the formation of miniaturized electrochemical immunosensors. Polypyrrole films implemented in various capacities in amperometric, conductometric, and potentiometric immunosensor design are reviewed. The acceptance of immobilization and detection approaches used recently in affinity sensors with critical analysis applied in certain techniques is discussed. The biologically active components (BAC) used for the creation of polypyrrole-based immunosensors are described briefly. Some future trends in the development of polypyrrole-based immunosensors are predicted, as well as possible directions discussed.

A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT. EDAS, an amine group-containing sol–gel solution, was utilized for its ability to stabilize the nanoparticles in solution. The developed model system was based on immobilized rabbit anti-mouse IgG-HRP (horseradish peroxidase) for reagentless detection of mouse IgG. The immunosensing platform was prepared by using Nafion for the immobilization of rabbit anti-mouse IgG-HRP and CNT–AuNPs hybrid nanocomposite on a glassy carbon electrode used for the detection of mouse IgG which provides a biocompatible microenvironment. The resulting CNT–AuNPs nanocomposite brings new capabilities for electrochemical devices by using the synergistic action of its electrocatalytic activity. The CNT–AuNPs were characterized using SEM, TEM, EIS, and AFM, and the analytical performance was monitored by differential pulse voltammetry. The detection limit of mouse IgG is 0.5 ng mL À1 (S/N ratio ¼ 3). In addition, the immunosensor efficiently allowed a specific electrochemical analysis of mouse IgG and easy discrimination of goat IgG, chicken IgG, and rabbit IgG.

Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quant...

in which the immunochemical reaction is coupled to a transducer. The fundamental basis of all immunosensors is the specificity of the molecular recognition of antigens by antibodies to form a stable complex. This is similar to the immunoassay methodology. Immunosensors can be categorized based on the detection principle applied. The main developments are electrochemical, optical, and microgravimetric immunosensors. In contrast to immunoassay, modern transducer technology enables the label-free detection and quantification of the immune complex. The analysis of trace substances in environmental science, pharmaceutical and food industries is a challenge since many of these applications demand a continuous monitoring mode. The use of immunosensors in these applications is most appropriate. Food chemists should take advantage of immunosensors in food and clinical diagnostics. There are many recent developments in the immunosensor field which have potential impacts. The future role of th...

Recent progress in the application of new 2D-materials-MXenes-in the design of biosensors, biofuel cells and bioelectronics is overviewed and some advances in this area are foreseen. Recent developments in the formation of a relatively new class of 2D metallically conducting MXenes opens a new avenue for the design of conducting composites with metallic conductivity and advanced sensing properties. Advantageous properties of MXenes suitable for biosensing applications are discussed. Frontiers and new insights in the area of application of MXenes in sensorics, biosensorics and in the design of some wearable electronic devices are outlined. Some disadvantages and challenges in the application of MXene based structures are critically discussed.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

A modular immunosensor device based on silicon technology with electrochemical detection is presented. The sensor surface is functionalized with the antigen estradiol using the streptavidin-biotin system. The immobilized antigen is recognized by ferrocene-labeled antibody molecules in a competitive assay format. The ferrocene redox centers can be detected electrochemically. In order to facilitate the electron transfer, a gold layer structured in nanometer dimensions is used as an electrode. The functionslued silicon chip will be integrated into a micromachined fluid transport system. The resulting immunosensor device for estradiol represents a prototype allowing easy adaptation to other biotinylated analytes since the immobilized streptavidin serves as a universal anchor.

Immunosensors are affinity ligand-based biosensor solid-state devices in which the immunochemical reaction is coupled to a transducer. The fundamental basis of all immunosensors is the specificity of the molecular recognition of antigens by antibodies to form a stable complex. This is similar to the immunoassay methodology. Immunosensors can be categorized based on the detection principle applied. The main developments are electrochemical, optical, and
microgravimetric immunosensors. In contrast to immunoassay, modern transducer technology enables the label-free detection and quantification of the immune complex. The analysis of trace substances in environmental science, pharmaceutical and food industries is a challenge since many of these applications demand a continuous monitoring mode. The use of immunosensors in these applications is most appropriate. Food chemists should take advantage of immunosensors in food and clinical diagnostics. There are many recent developments in the immunosensor field which have potential impacts. The future role of this technique in intra-laboratory, as well as
bedside testing, will become even more important as the food laboratory is faced with increasing pressure to contain costs. Objective of this paper is to give a general overview of the possible application of immunosensors to the food analysis field.

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

A novel label-free electrochemical impedimetric immunosensor for sensitive detection of ochratoxin A (OTA) was reported. A two-step reaction protocol was elaborated to modify the gold electrode. The electrode was first derivatized by electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt (4-CPDS) in acidic aqueous solution yielded stable 4-carboxyphenyl (4-CP) monolayer. The ochratoxin A antibody was then immobilized making use of the carbodiimide chemistry. The steps of the immunosensor elaboration and the immunochemical reaction between ochratoxin A and the surface-bound antibody were interrogated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance change, due to the specific immuno-interaction at the immunosensor surface was utilized to detect ochratoxin A. The increase in electron-transfer resistance ( R et ) values was linearly proportional to the concentration of OTA in the range of 1-20 ng mL −1 , with a detection limit of 0.5 ng mL −1 .

The genus enterovirus is constituted by a wide number of viral species having in common many of morphological and genetic characters. These viruses present a high epidemiological power and are in question of various human diseases. The absence of easy and standardized technique for their detection justify the need to develop new techniques of diagnosis. In this work, we describe the development of an immunosensor based on functionalized gold electrode allowing enteroviruses detection. The biosensor is based on the grafting of specific monoclonal enterovirus antibodies onto functionalized gold electrode. Each step of biosensor construction was characterised by electrochemical impedance spectroscopy, fitted with an equivalent electric circuit and the antibody-virus interaction was measured with a detection limit of 10 viral particles (vp) or 1.4 vp/mL.

http://www.ingentaconnect.com/content/asp/senlet/2009/00000007/00000005/art00045

Aflatoxins are toxic carcinogenic secondary metabolites produced predominantly by two fungal species: Aspergillus flavus and Aspergillus parasiticus. These fungal species are contaminants of foodstuff as well as feeds and are responsible for aflatoxin contamination of these agro products. The toxicity and potency of aflatoxins make them the primary health hazard as well as responsible for losses associated with contaminations of processed foods and feeds. Determination of aflatoxins concentration in food stuff and feeds is thus very important. However, due to their low concentration in foods and feedstuff, analytical methods for detection and quantification of aflatoxins have to be specific, sensitive, and simple to carry out. Several methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectroscopy, enzyme-linked immune-sorbent assay (ELISA), and electrochemical immunosensor, among others, have been described for detecting and quant...

Aquifers used for drinking water production require regular monitoring for organic pollutants. Pollutant levels and pollutant patterns may change rapidly especially in surface water. Monitoring systems capable of unattended and automated operation are desirable e.g. at pumping sites. In this paper we report on a study of the application of immunoanalytical techniques for exible and automated multiresidue testing. A solid phase¯uorescence immunoassay with immobilised analyte derivate and free,¯uorescence labelled antibody is used. Two optical transducers were tested: A simple`slab'-waveguide made of sheet glass and an integrated optical (IO) waveguide. Bulk¯uorophore excitation was used to estimate the performance of each transducer. Both transducers allow an antibody surface coverage of less than 1% of a monolayer of protein to be detected. The direct and covalent immobilisation of analyte derivates at the transducer surface for a binding inhibition assay approach is compared to a competitive assay with immobilisation of analyte derivates via an auxiliary antibody conjugate. The use of this auxiliary system allows the testing of different analytes at the same transducer surface. Atrazine was selected as a model analyte for the ®rst trials. The ELISA type assay gives a test midpoint at 2.2 mg/l and an estimated limit of detection of 0.3 mg/ l. The¯uoroimmunoprobe with a binding inhibition assay has a test midpoint for atrazine at about 6 mg/l. In the competitive assay with an auxiliary antibody conjugate signal levels were reduced by a factor of two and competition of free atrazine was poor. Titration with free analyte derivate (atrazine caproic acid) con®rmed that this may be optimised by changing the competing derivate.

A novel label-free electrochemical impedimetric immunosensor for sensitive detection of ochratoxin A (OTA) was reported. A two-step reaction protocol was elaborated to modify the gold electrode. The electrode was first derivatized by electrochemical reduction of in situ generated 4-carboxyphenyl diazonium salt (4-CPDS) in acidic aqueous solution yielded stable 4-carboxyphenyl (4-CP) monolayer. The ochratoxin A antibody was then immobilized making use of the carbodiimide chemistry. The steps of the immunosensor elaboration and the immunochemical reaction between ochratoxin A and the surface-bound antibody were interrogated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance change, due to the specific immuno-interaction at the immunosensor surface was utilized to detect ochratoxin A. The increase in electron-transfer resistance (R et) values was linearly proportional to the concentration of OTA in the range of 1-20 ng mL −1 , with a detection limit of 0.5 ng mL −1 .

Pesticides, due to their intensive use and their peculiar chemical features, can persist in the environment and enter the trophic chain, thus representing an environmental risk for the ecosystems and human health. Although there are several robust and reliable standard analytical techniques for their monitoring, the high frequency of contamination caused by pesticides requires methods for massive monitoring campaigns that are capable of rapidly detecting these compounds in many samples of different origin. Immunosensors represent a potential tool for simple, rapid, and sensitive monitoring of pesticides. Antibodies coupled to electrochemical or optical transducers have resulted in effective detection devices. In this review, the new trends in immunosensor development and the application of immunosensors for the detection of pesticides of environmental concern—such as glyphosate, organophosphates, and neonicotinoids—are described.

This paper presents the detailed design and characterisation of a regenerable integrated optical surface plasmon resonance immunoprobe as a detector for the triazine herbicide simazine. A sensor design theoretically optimised for use in the aqueous environment is presented and its fabrication described. Experimental results on the sensitivity to changes in bulk refractive index of the analyte and on non-specific binding of ovalbumin are presented. Binding inhibition immunoassays were conducted for simazine and the lower limit of detection determined to be 0.16 mg/l using anti-simazine IgG antibodies and 0.11 mg/l using anti-simazine Fab fragments. A sample test cycle of 20 min was established.

Dengue is an arbovirus disease transmitted mainly by Aedes mosquitoes. As dengue shares
similar clinical symptoms with other infectious diseases, prompt and accurate diagnosis is pivotal
to clinicians’ decisions on appropriate management. Conventional diagnostic tests to detect the
dengue-specific IgM antibody are limited in their performance and ease of use. To address these
issues, we developed and evaluated a biosensor based on screen-printed carbon electrodes (SPCEs)
for the detection of dengue-specific immunoglobulinM(IgM) antibodies. Various optimisations were
performed in order to increase the sensitivity and specificity of the biosensor. For optimal and proper
orientation of the paratope sites of goat anti-human IgM capture antibodies (GAHICA), various antibody
techniques, including passive, covalent, protein A, protein G and streptavidin/biotin systems,
were tested on the SPCEs. The assay reagents for the biosensor were also optimised prior to its evaluation.
Analytical sensitivity evaluation was carried out using pooled sera, while analytical specificity
evaluation was conducted on a panel of six non-dengue serum samples. Subsequently, diagnostic
sensitivity and specificity evaluation were performed using 144 reference samples. Electrochemical
current signals generated from H2O2 catalysed by HRP-labelled anti-dengue detection antibodies
were measured using the chronoamperometric technique. With a limit of detection (LOD) of 106
serum dilution, the analytical sensitivity of the developed biosensor was 10 times higher than commercial
ELISA. The analytical specificity of this dengue IgM biosensor was 100%. Similarly, the
biosensor’s diagnostic performance was 100% for sensitivity, specificity, positive predictive value
(PPV) and negative predictive value (NPV). These findings suggest that the developed biosensor has
a great potential to be used to diagnose dengue after seroconversion.

Aim. Engineering of recombinant Staphylococcal protein A with cysteine residue (SPA-Cys) for preparation of affi nity chromatography stationary phase and formation of bioselective element of immunosensor. Methods. DNA sequences encoding IgG-binding region of SPA, His-tag and cysteine were genetically fused and expressed in E. coli. SPA-Cys was immobilized on maleimide-functionalized silica beads for af-fi nity chromatography stationary phase preparation and on a gold sensor surface as a bioselective element of immunosensor. Results. SPA-Cys was expressed at a high-level in a soluble form. The target protein was purifi ed and showed a high IgG-binding activity. The capacity of the obtained SPA-Cys-based affi nity chromatography stationary phase was 10-12 mg of IgG /ml. The purity of eluted IgG was more than 95 % in one-step purifi cation procedure. The developed SPA-Cys-based bioselective element of immunosensor selectively interacted with human IgG and did not interact with the control proteins. Conclusions. The recom-binant Staphylococcal protein A with cysteine residue was successfully used for the preparation of affi nity chromatography stationary phase and formation of the bioselective element of immunosensor. K e y w o r d s: antibodies, recombinant Staphylococcal protein A, protein immobilization, affi nity chromatography , immunosensor, surface plasmon resonance.

We report here the development of a new assay for the detection of ochratoxin A (OTA) based on the use of its dechlorinated analogue, ochratoxin B (OTB), in a displacement immunoassay. OTB was immobilised on controlled-pore glass beads followed by the binding of anti-OTA antibody, with anti-IgG antibody peroxidase conjugate used as a label. In this manner, an original bio-sensing material was obtained. Upon incubation of this material with OTA, the toxin competes with OTB for the binding sites of the anti-OTA antibodies and releases the antibody-tagged peroxidase complex into the solution. Compared to classic competitive immunoassays, this newly developed displacement immunoassay presents a similar detection limit and assay time. Moreover, the detection, based on the activity of the horseradish peroxidase, is performed for the first time in situ using wine samples.