Use Of Immunosensors Research Articles

Immunosensors-The Future of Pathogen Real-Time Detection.

Pathogens and their toxins can cause various diseases of different severity. Some of them may be fatal, and therefore early diagnosis and suitable treatment is essential. There are numerous available methods used for their rapid screening. Conventional laboratory-based techniques such as culturing, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) are dominant. However, culturing still remains the "gold standard" for their identification. These methods have many advantages, including high sensitivity and selectivity, but also numerous limitations, such as long experiment-time, costly instrumentation, and the need for well-qualified personnel to operate the equipment. All these existing limitations are the reasons for the continuous search for a new solutions in the field of bacteria identification. For years, research has been focusing on the use of immunosensors in various types of toxin- and pathogen-detection. Compared to the conventional methods, immunosensors do not require well-trained personnel. What is more, immunosensors are quick, highly selective and sensitive, and possess the potential to significantly improve the pathogen and toxin diagnostic-processes. There is a very important potential use for them in various transport systems, where the risk of contamination by bioagents is very high. In this paper, the advances in the field of immunosensor usage in pathogenic microorganism- and toxin-detection, are described.

Screen-Printed Electrodes on Tyvek Substrate as Low-Cost Device to Applications in Alzheimer’s Disease Detection

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by impairment of cognitive functions and memory deterioration, which requires an early diagnosis for effective treatment. The use of immunosensors to detect Alzheimer’s disease biomarkers stand out as a quick and cheap alternative for early detection of the disease. The development of Screen-Printed Electrodes (SPEs) meets a growing demand in the market for applications such as signal transducers in biosensor devices. In this work was development a method for fabrication of low cost SPE for application in the detection of Alzheimer’s disease through autoantibodies. It was produced microelectrodes on polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF) and high-density polyethylene (HDPE) manufactured by DuPont Tyvek® substrates. SPEs produced on Tyvek® substrates have shown promising results for low-cost, disposable and flexible sensors. The carbon paste showed excellent adhesion to Tyvek® substrate and the electrodes produced showed an electrochemical performance comparable to commercial electrodes, besides reproducible. The detection results showed that it is possible to detect anti-Aβ40 autoantibodies in real samples of serum and cerebrospinal fluid using the electrode modified with two bilayers of (PEI/(DDPG + Aβ40)) since the capacitance increased more in positive sample with the presence of autoantibody than in negative samples.

Fully printed and flexible multi-material electrochemical aptasensor platform enabled by selective graphene biofunctionalization

The demand for flexible biochemical sensors has increased with advances in computational functionality and wireless communication. Advances in materials science and biochemistry have enabled the development and fabrication of biosensors for selective detection of biological analytes leveraging ink-printed technologies, including in flexible form-factors. However, despite these advances, minimal effort has been devoted to translating the multi-material, three-electrode electrochemical cell, which is widely regarded as the standard for laboratory-scale studies, into a flexible form-factor for use in immunosensors, especially in a manner that is compatible with rapid and scalable additive manufacturing. Here, we report a fully printed and flexible electrochemical non-enzymatic immunosensor platform that integrates four chemically compatible inks and a non-covalent, two-step biofunctionalization scheme. The robustness of the platform is demonstrated using a model aptasensor that enables lysozyme detection using both electrochemical impedance spectroscopy and square wave voltammetry. The flexible, fully ink-printed aptasensor shows competitive performance to commercially available rod/disc electrodes in a bath cell. Overall, this work establishes a methodology for high-throughput fabrication of robust, flexible, multi-material, three-electrode immunosensors that can be generalized to a range of biosensor applications.

Japanese encephalitis virus: a review on emerging diagnostic techniques.

Japanese Encephalitis Virus (JEV) is the most common Flavivirus based mosquito borne viral encephalitis in the world, especially in countries of South-East Asia. The conventional methods such as Enzyme-Linked Immunosorbent Assays (ELISA), Reverse Transcriptase Polymerase Chain Reaction (RT-PCR), Plaque Reduction Neutralization Test and virus isolation are still in use today but new advances are being made to develop more efficient, inexpensive, quicker, sensitive and time-saving techniques to detect JEV. Some of these include the use of immunosensors, both lateral flow based assays and electrochemical, as well as the incorporation of nanotechnology into biosensors to develop highly sensitive detection tools. This review focuses on the recent advances that have been made to diagnose Japanese Encephalitis Virus which are critical in breaking the link to zoonotic transmission into the human population where humans are dead-end hosts.

ВИВЧЕННЯ КЛАСИФІКАЦІЇ ІММУНОСЕНСОРІВ З ПОГЛЯДУ НА МЕДИЧНІ ЗАВДАННЯ

Immunosensors and immunotests are commonly used in medicine, where blood, urine or saliva samples enable concentrations of morphine, progesterone, estradiol, dopamine, insulin to be determined.In this work, the use of immunosensors for the following medical problems is considered: for the quantitative detection of alpha-fetoprotein, for determination of p53 protein in urine for diagnostics bladder cancer, for amperometric determination of carcinoembryonic antigen, for the determination of galectin-3, as biomarker of heart failure, for detecting hepatitis B surface antigen, for sensitive detection of tumor marker for determination of serum level in breast cancer patients.

Structural Characterization of Nanoyeast Single-Chain Fragment Variable Affinity Reagents

Nanoyeast single-chain variable fragments (nanoyeast-scFv) are a new class of low-cost and stable protein capture agents developed as alternatives to full length monoclonal antibodies for use in immunosensors. Physical characteristics that impart nanoyeast-scFv with these advantages have yet to be investigated. We investigate the structure, size and surface loading of nanoyeast-scFv to better understand its ability to specifically and sensitively capture proteins of interest while retaining activity in solution. Nanoyeast-scFv fragments were found to be globular in structure and heterogeneous in size, typically <100 nm, and were found to aggregate in solution. Optimal fragment size was determined to be <220 nm, with larger fragments interfering with the electrochemical biosensor. We hypothesize that the stability of nanoyeast-scFv is conferred in part by components of the yeast cell wall fragments, which provide stability to the associated scFv both during selection, lyophilization, and rehydration.

Review: Advancements and application of immunosensors in the analysis of food contaminants

Azam MS, Rahman MRT, Lou Z, Tang Y, Raqib SM, Jothi JS. 2014. Advancements and application of immunosensors in the analysis of food contaminants. Nusantara Bioscience 6: 186-195. 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.

Optical immunosensors for environmental monitoring: How far have we come?

Immunosensing has proved to be a very interesting research area. This review discusses what has actually been achieved in the field of optical immunosensing for environmental screening, and what still needs to be done. The review is presented from a practical point of view. In terms of the basic design of the immunosensor, there is a trend towards decreasing assay time; indeed, this has been reduced from 15-20 minutes to less than 5 minutes. Another goal is to simplify the manifold, and label-free approaches combining indirect assay formats and the detection of antibody binding are popular. Rapid displacement assays have also been investigated thoroughly. In terms of some important features of immunosensing devices, the reusability of the sensing element has been studied in great depth, and working lifetimes of more than five hundred assays can now be found for all assay formats. Multianalyte assays are now being investigated, and current systems are able to monitor 2-3 target compounds, although this number is set to increase greatly (to >30) in the near future. In this sense, an increasing number of publications can be found on microarrays intended for multianalyte determinations. The application of immunosensing to real situations is the main challenge. Immunosensors are barely commercialized and are yet to be established as research or routine tools, due to a lack of validated protocols for a wide range of sample matrices. Regarding compounds considered as analytes, some significant pollutants such as dioxins or pharmaceuticals are rarely chosen as targets, although the current tendency is towards a broader spectrum of analytes. New immunoreagents should be raised for these compounds, for use in immunosensors that can be used as screening tools.

Regeneration of ethyl parathion antibodies for repeated use in immunosensor: a study on dissociation of antigens from antibodies

Reliable analysis using an immunosensor strongly depends on the specificity, activity, and sensitivity of the antibody. Immobilization of antibody on the solid matrix enables its repeated use, for which it is required to dissociate the antigens and antigen–enzyme conjugate from the immobilized antibody matrix after each use and while doing so, a maximum retention of activity and specificity are crucial requirements. In the present investigation, on the development of an immunosensor for the organophosphorus pesticide ethyl parathion (EP) using EP antibodies, different dissociating agents such as organic solvents, detergents and acidic buffers, that is, dimethyl sulphoxide (DMSO), Tween-20, cetyl trimethylammonium bromide (CTAB), methanol, chloroform, guanidium chloride (GdmCl), glycine–HCl (Gly–HCl) buffer in the pH range of 1.5–3.0, pierce buffer and combination of DMSO and methanol in phosphate buffer and Gly–HCl buffer and salts like NaCl and MgCl 2 were used. Generally about 50–60% dissociation was obtained with some degree of denaturation of the antibody immobilized on the sepharose matrix. However, 1% DMSO in combination with 0.2 M Gly–HCl buffer at a pH of 2.3 showed 97% dissociation and the immobilized antibody retained sufficient activity to carry out 14 reproducible assays for EP.

Characterization and performance evaluation of in vivo and in vitro produced monoclonal anti-TNT antibodies for the detection of TNT

In this paper are the experimental results used to characterize four distinct monoclonal anti-TNT antibodies (in vivo and in vitro cloned) for potential use in a field-portable immunosensor. Direct and competitive enzyme-linked immunosorbent assays (ELISA) were performed to determine their affinity for TNT and a fluorescently labeled analog of TNT for use in an immunosensor. Effective concentrations (EC 50), inhibition concentration (IC 50) and cross-reactivity measurements to related nitroaromatics (e.g., 2,4,6-trinitrobenzene [TNB], methyl-2,4,6-trinitrophenyl nitramine [tetryl], 2-amino-4,6-dinitrotoluene [2A-4,6-DNT], 2,4-dinitrotoluene [2,4-DNT] and 1,3-dinitrotoluene [1,3-DNT]) were measured. Final characterization of the monoclonal antibodies was based on performance (measured by fluorescence dose response) using a fluorescence-based microcapillary displacement assay. Analytical techniques showed a high degree of affinity for TNT and varying degrees of cross-reactivity with each respective monoclonal antibody. Microcapillary displacement immunoassays with each of the antibodies resulted in detection capabilities at the lowest applied TNT concentration (10 ng/ml).

Environmental Chemistry: The Immunoassay Option

Abstract Scientific awareness and public concern about the state of our environment have led to unprecedented demands on analytical laboratories. There is now much interest in strategies that will help to lower costs and improve efficiency. Immunoassay (IA) techniques, which are widely used in clinical chemistry, could play a key role in the laboratory of the future. IA screening techniques for the detection of a broad variety of pollutants, including pesticides and industrial contaminants, are reviewed. IAs are best suited to the analysis of large sets of samples. A majority of the methods are sufficiently sensitive and selective for environmental applications. Some approaches that might help improve the sensitivity of IAs so that ultra-trace analytes can be detected are considered. Analytes can usually be detected in water samples with little or no sample preparation. In many cases, an extraction step, which is sometimes followed by a simple clean-up step, suffices for solid matrices. Hydrophobic analytes, such as the polychlorinated dibenzo-p-dioxins, are the exception. Recent advances in the validation of environmental IAs, which should improve the confidence of the unfamiliar analyst, are reviewed. IA kits are available for analysts without the resources to develop their own assays. Some interesting trends that are reviewed include the use of immunosensors for the direct detection of contaminants, the use of immunoaffinity chromatography for the one-step purification of analytes, and the environmental application of electrochemical and flow injection immunoassays. IAs have the potential to boost productivity and release costly instruments for use in the quantification of positive samples.