Toll-like receptors for pathogen detection in water: challenges and benefits

The need for effective and efficient methods for pathogen detection in water is as serious as ever due to the health risk posed to human population by the consumption of pathogen-contaminated water. One of the important research streams which have been focused on by researchers for development of novel techniques for this purpose is biosensor technologies. Using different bio-recognition elements and transduction methodologies, biosensors have the potential to detect their analyte of interest in a fast and highly specific manner. Different pathogenic agents can be recognised by toll-like receptors (TLRs). The innate immune system of higher organisms employs TLRs for triggering intracellular signalling and induction of the expression of immune response genes. In this report, we explore the challenges associated with employing TLRs for pathogen detection in water samples. Although methods using TLR expressing cells also have been discussed, the focus of this review is on using TLR proteins as the bio-recognition elements in biosensors.     

Microfluidic designs and techniques using lab-on-a-chip devices for pathogen detection for point-of-care diagnostics

Effective pathogen detection is an essential prerequisite for the prevention and treatment of infectious diseases. Despite recent advances in biosensors, infectious diseases remain a major cause of illnesses and mortality throughout the world. For instance in developing countries, infectious diseases account for over half of the mortality rate. Pathogen detection platforms provide a fundamental tool in different fields including clinical diagnostics, pathology, drug discovery, clinical research, disease outbreaks, and food safety. Microfluidic lab-on-a-chip (LOC) devices offer many advantages for pathogen detection such as miniaturization, small sample volume, portability, rapid detection time and point-of-care diagnosis. This review paper outlines recent microfluidic based devices and LOC design strategies for pathogen detection with the main focus on the integration of different techniques that led to the development of sample-to-result devices. Several examples of recently developed devices are presented along with respective advantages and limitations of each design. Progresses made in biomarkers, sample preparation, amplification and fluid handling techniques using microfluidic platforms are also covered and strategies for multiplexing and high-throughput analysis, as well as point-of-care diagnosis, are discussed.     

Biosensors for pharmaceuticals based on novel technology

The availability of pharmaceuticals to treat and to prevent disease has brought great benefit. Nevertheless, attention is being drawn to the uncontrolled use and careless disposal of medications for humans and animals. These compounds and their metabolites are found in the environment and foodstuffs, with possible adverse risks to human health.Detection of pharmaceuticals and residues in environmental and biological matrices has become a priority for governmental agencies. However, current analytical methods capable of detecting pharmaceuticals at very low levels require time-consuming sample preparation, concentration and/or extraction prior to analysis.Biosensors offer several advantages over existing techniques (e.g., less time, high-throughput screening, improved sensitivity, real-time analysis and the possibility of developing label-free detection methods and devices). Also, incorporation of nanotechnology into biosensor systems may increase the speed and the capability of the diagnostic methods. Moreover, the possibility of using biosensor systems in different configurations allows us envisaging their implementation as point-of-care systems or multiplexed devices.This review provides a general overview of the progress, the limitations and the future challenges of biosensors for detecting pharmaceuticals.     

Mycotoxins Detection Based on Electrochemical Approaches

Electrochemical biosensors have attracted much attention in mycotoxin bioanalysis. In this review, three electrochemical biosensor technologies for mycotoxins were reviewed, including general electrochemistry, photoelectrochemistry, and electrochemiluminescence. Based on the classification of multiple electrochemical detection methods, the design schemes, recognition mechanism and probe materials were described in detail. Moreover, the characteristics and limitations of these electrochemical biosensors were summarized. The challenges and future trends of electrochemical biosensor development in mycotoxin bioanalysis were also briefly discussed in the end. This review is expected to provide some inspirations for point-of-care testing in electrochemical sensors for mycotoxins and further electrochemical analysis application.     

Recent developments in rapid multiplexed bioanalytical methods for foodborne pathogenic bacteria detection

Foodborne illnesses caused by pathogenic bacteria represent a widespread and growing problem to public health, and there is an obvious need for rapid detection of food pathogens. Traditional culture-based techniques require tedious sample workup and are time-consuming. It is expected that new and more rapid methods can replace current techniques. To enable large scale screening procedures, new multiplex analytical formats are being developed, and these allow the detection and/or identification of more than one pathogen in a single analytical run, thus cutting assay times and costs. We review here recent advancements in the field of rapid multiplex analytical methods for foodborne pathogenic bacteria. A variety of strategies, such as multiplex polymerase chain reaction assays, microarray- or multichannel-based immunoassays, biosensors, and fingerprint-based approaches (such as mass spectrometry, electronic nose, or vibrational spectroscopic analysis of whole bacterial cells), have been explored. In addition, various technological solutions have been adopted to improve detectability and to eliminate interferences, although in most cases a brief pre-enrichment step is still required. This review also covers the progress, limitations and future challenges of these approaches and emphasizes the advantages of new separative techniques to selectively fractionate bacteria, thus increasing multiplexing capabilities and simplifying sample preparation procedures.

Biosensors with label-free detection designed for diagnostic applications

Since the first biosensor was introduced in 1962 by Clark and Lyons, there has been increasing demand for such analytical devices in diagnostic applications. Research initially focussed mainly on detector principles and recognition elements, whereas the packaging of the biosensors and the microfluidic integration has been discussed only more recently. However, to obtain a user-friendly and well-performing analytical device, those components have to be considered all together. This review outlines the requirements and the solutions suggested for the integration of suitable biosensors in packaging and the integration of those encapsulated biosensors into a microfluidic surrounding resulting in a complete and efficient analytical device for diagnostic applications. The components required for a complete biosensor instrument are described and the latest developments which meet the requirements for diagnostic applications, such as single-use components and arrays for multiparameter detection, are discussed. The current state and the future of biosensors in the field of clinical diagnostics are outlined, particularly on the basis of label-free assay formats and the detection of prominent biomarkers for cancer and autoimmune disorders.     

Integration of electrochemistry in micro-total analysis systems for biochemical assays: Recent developments

Micro-total analysis systems (μTAS) integrate different analytical operations like sample preparation, separation and detection into a single microfabricated device. With the outstanding advantages of low cost, satisfactory analytical efficiency and flexibility in design, highly integrated and miniaturized devices from the concept of μTAS have gained widespread applications, especially in biochemical assays. Electrochemistry is shown to be quite compatible with microanalytical systems for biochemical assays, because of its attractive merits such as simplicity, rapidity, high sensitivity, reduced power consumption, and sample/reagent economy. This review presents recent developments in the integration of electrochemistry in microdevices for biochemical assays. Ingenious microelectrode design and fabrication methods, and versatility of electrochemical techniques are involved. Practical applications of such integrated microsystem in biochemical assays are focused on in situ analysis, point-of-care testing and portable devices. Electrochemical techniques are apparently suited to microsystems, since easy microfabrication of electrochemical elements and a high degree of integration with multi-analytical functions can be achieved at low cost. Such integrated microsystems will play an increasingly important role for analysis of small volume biochemical samples. Work is in progress toward new microdevice design and applications.     

A Microdialysis Probe Coupled with A Miniaturized Thermal Glucose Sensor for In Vivo Monitoring

Abstract

A miniaturized thermal flow injection analysis biosensor has been coupled with a microdialysis probe for continuous subcutaneous glucose monitoring. Thermal biosensors are based on the principle of measuring the heat evolved during enzyme catalysed reactions. The system presented here consists of a miniaturized thermal biosensor with a small column containing coimmibolized glucose oxidase and catalase. The analysis buffer passes through the column at a flow rate of 60μL/min via an 1μL sample loop which is connected to a microdialysis probe.

Invitro results showed constant permeability of the probe and stability of the biosensor response during 24 hours. The response time was 85 sec giving a sample rate of 42 samples/hour.

During a load experiment, the glucose profile in a healthy volunteer was followed both in the subcutaneous tissue and blood using the microdialysis set-up proposed and comparing to blood glucose analyser.     

Engineered Nanomaterial Assisted Signal‐amplification Strategies for Enhancing Analytical Performance of Electrochemical Biosensors

The design and development of modern biosensors for sensitive and selective detection of various biomarkers is important in diversified arenas including healthcare, environment, and food industries etc. The requirement of more robust and reliant biosensors lead to the development of various sensing modules. The nanomaterials having specific optical, electrical, and mechanical strength can pave the way towards development of ultrafast, robust, and miniaturized modules for biosensors. It can provide not only the point‐of‐care applicability but also has tremendous commercial as well as industrial justification. In order to improve the performance of the sensor systems, various nanostructure materials have been readily studied and applied for development of novel biosensors. In the last few years, researchers are engaged on harnessing the unique atomic and molecular properties of advance‐engineered materials including carbon nanotubes, graphene nanosheets, metal nanoparticles, metal oxide nanoparticles, and their nano‐conjugates. In view of such recent developments in nanomaterial engineering, the current review has been formulated emphasizing the role of these materials in surface engineering, biomolecule conjugation, and signal amplification for development of various ultrasensitive and robust biosensors having commercial as well as industrial viability. Attention is given on the electrochemical biosensors incorporating various nanomaterials and their conjugates. Importance of nanomaterials in the analytical performance of the various biosensor has also been discussed. To put a perceptive insights on the importance of various nanomaterials, an extended table is incorporated, which includes probe design, analyte, LOD, and dynamic range of various electrochemical biosensors.     

电化学DNA生物传感器*

对特异DNA序列的检测在基因相关疾病的诊断、军事反恐和环境监测等方面均具有非常重要的意义,DNA传感器的研究就是为了满足对特异DNA序列的快速、便捷、高灵敏度和高选择性检测的需要。近年来涌现出了多种传感策略,根据检测方法的不同可以大致分为光学传感器、电化学传感器、声学传感器等。由于电化学检测方法本身所具有的灵敏、快速、低成本和低能耗等特点,电化学DNA传感器已成为一个非常活跃的研究领域并在近几年中得到了快速发展。本文概括了近年来在DNA传感器的重要分支——电化学DNA传感器领域内的一些重要进展,主要包括DNA探针在传感界面上的固定方法和各种电化学DNA杂交信号的检测方法。     

Analysis of the evolution of the detection limits of electrochemical DNA biosensors

In this paper we critically review detection limits of electrochemical DNA biosensors enabling DNA detection without target labelling. The review includes transduction principles and latest breakthroughs. To compare the efficiency of each type of electrochemical DNA biosensor, a simple DNA biosensors classification is established on the basis of the nature of the bio-electrochemical transduction.     

Catalytic electrooxidation of NADH for dehydrogenase amperometric biosensors

The developments in the techniques of NADH catalytic oxidation relevant for incorporation in amperometric biosensors with dehydrogenase enzymes are reviewed with special emphasis in the years following 1990. The review stresses the direct electro-catalytic methods of NAD⁺ recycling as opposed to enzymatic regeneration of the coenzyme. These developments are viewed and evaluated from a mechanistic perspective of recycling of NADH to enzymatically active NAD⁺, and from the point of view of development of technologically useful reagentless dehydrogenase biosensors. An effort is made to propose a method for the standardization of evaluation of new mediating and direct coenzyme recycling schemes. A perspective is given for the requirements that have to be met for successful biosensor development incorporating dehydrogenase enzymes that open the analytical possibilities to a number of new analytes. The intrinsic limitations of the system are finally discussed and a view of the future of the field is presented.     

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.     

In Vivo Electrochemical Biosensors for Reactive Oxygen Species Detection: A Mini-Review

Due to the significance of reactive oxygen species (ROS) in numerous physiological processes including pathogen response, apoptosis, and induction of defense genes, various methods have been developed for their quantitative analysis. However, the conventional methods using exogenous tracers lack the capability to conduct real-time in vivo measurements. The electrochemical biosensors have shown their potentials for in vivo applications with the rapid and reagentless detection processes. In this article, electrochemical biosensors that are capable of making in vivo ROS detections are reviewed. The different configurations of these biosensors with corresponding strategies to enhance sensitivity and selectivity are discussed in detail. With further studies to promote the biosensor performance, these devices promise to provide more facile ways for ROS research in life sciences.     

Formaldehyde-sensitive conductometric sensors based on commercial and recombinant formaldehyde dehydrogenase

Novel formaldehyde-sensitive conductometric biosensors have been developed that are based on commercial bacterial formaldehyde dehydrogenase (FDH) from Pseudomonas putida and recombinant formaldehyde dehydrogenase (rFDH) from the yeast Hansenula polymorpha as the bio-recognition elements. The bio-recognition membranes have mono-layer architecture and consist of enzyme cross-linked with albumin and of the cofactors NAD (for FDH-based sensor) or NAD and glutathione (for rFDH-based sensor). This architecture of the biosensor allows the determination of formaldehyde without adding NAD and glutathione to the analyzed sample at every analysis and conducting measurements on the same transducer without cofactors regeneration since the bio-membrane contains it at high concentration (100 mM for NAD and 20 mM for glutathione). The response is linear in the range from 10 to 200 mM of formaldehyde concentration depending on the enzyme used. The dependence of the biosensor output signals on pH and buffer concentration as well as operational/storage stability and selectivity/specificity of the developed conductometric biosensors have been investigated. The relative standard deviation of the intra-sensor response did not exceed 4% and 10% for rFDH- and FDH-based sensors, respectively. The relative standard deviation of the inter-sensor response constituted 20% for both dehydrogenases used. The biosensors have been validated for formaldehyde detection in some real samples of pharmaceutical (Formidron), disinfectant (Descoton forte) and an industrial product (Formalin). A good correlation does exist between the concentration values measured by the conductometric biosensor developed in this work, an enzymatic method, amperometric biosensors developed earlier, and standard analytical methods of formaldehyde determination.     

Improved Performance of the Potentiometric Biosensor for the Determination of Creatinine

Abstract

Contemporary methods of analyzing creatinine engage chemicals harmful to the environment and generate large volumes of waste disposals. By introducing a membrane‐based potentiometric biosensor with immobilized creatinine deaminase, the measurements can be performed by miniaturized portable devices that are easy to handle and allow rapid analysis with minimum consumption of chemicals. Thus, the enzymatic creatinine biosensors were revisited and optimized with respect to repeatability, sensitivity, limit of detection (LOD), and response time. A detection limit of 0.3 µM and a sensitivity of 58.78±0.03 mV (23.5°C) were obtained in tris buffer at pH=7.4 after introduction of shielding of all electronics and software filtering. Measurements performed by flow injection analysis (FIA) showed that the response time could be lowered to approximately 30 sec using sample volumes of 30 µl. Interferences were corrected for by application of the Nicolsky‐Eisenman equation, thus allowing determination of creatinine in matrices resembling those of clinical measurements. Investigations of sandwich structures showed that the sensitivity decreased as a function of the number of membranes on top of the immobilized layer of active creatinine deaminase. It was thus shown that the sensitivity depends on the distance of diffusion of species from the sample solution through the membranes to the enzyme.     

Advances in pesticide biosensors: current status, challenges, and future perspectives

Public concern over pesticide residues has been increasing dramatically owing to the high toxicity and bioaccumulation effects of pesticides and the serious risks that they pose to the environment and human health. It is therefore crucial to monitor pesticide residues by using various analytical methods and techniques, especially highly sensitive, highly selective, simple, rapid, cost-effective, and portable ones. Biosensor strategies have become research hotspots and ideal candidates for pesticide detection, having such features as high sensitivity, fast response, robustness, low cost and miniaturization, as well as in situ and real-time monitoring. This review covers advances in the design and fabrication of biosensors for pesticide detection since 2005. Special emphasis is placed on the state-of-art selection of receptors, the use of different transduction techniques and fast screening strategies, and the application of various biosensors developed in food and environmental safety. Both advantages and drawbacks of these techniques are then summarized. Finally, challenges, strategies, and perspectives in further developing pesticide biosensors are also discussed.

Miniaturized electrochemical sensors and their point-of-care applications

Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.     

表面等离子体共振技术在蛋白质-蛋白质相互作用研究中的应用

表面等离子共振(SPR)近年来迅速发展为用于分析生物分子相互作用的一项技术.该技术无需标记、特异性强、灵敏度高、样品用量小,可实现在线连续实时检测.目前SPR已被广泛应用于免疫学、蛋白质组学、药物筛选、细胞信号转导、受体/配体垂钓等领域.该文阐述了基于表面等离子体共振技术生物传感器的基本原理和技术流程,综述了SPR在蛋白质-蛋白质相互作用动力学研究、蛋白质结构及功能研究、蛋白质突变和碎片分析、信号转导中的应用以及SPR在蛋白质-蛋白质相互作用研究中的多项关键技术.指出SPR通过与光谱、电化学等多技术联用后,可以获得更加详实的信息.