Array biosensor for detection of biohazards

Emerging bioanalytical sensors for rapid and close-to-real-time detection of priority abiotic and biotic stressors in aquaculture and culture-based fisheries

Abiotic stresses of various chemical contamination of physical, inorganic, organic and biotoxin origin and biotic stresses of bacterial, viral, parasitic and fungal origins are the significant constraints in achieving higher aquaculture production. Testing and rapid detection of these chemical and microbial contaminants are crucial in identifying and mitigating abiotic and biotic stresses, which has become one of the most challenging aspects in aquaculture and culture-based fisheries. The classical analytical techniques, including titrimetric methods, spectrophotometric, mass spectrometric, spectroscopic, and chromatographic techniques, are tedious and sometimes inaccessible when required. The development of novel and improved bioanalytical methods for rapid, selective and sensitive detection is a wide and dynamic field of research. Biosensors offer precise detection of biotic and abiotic stressors in aquaculture and culture-based fisheries within no time. This review article allows filling the knowledge gap for detection and monitoring of chemical and microbial contaminants of abiotic and biotic origin in aquaculture and culture-based fisheries using nano(bio-) analytical technologies, including nano(bio-)molecular and nano(bio-)sensing techniques.

Advances in Optical Detection of Human-Associated Pathogenic Bacteria

Bacterial infection is a global burden that results in numerous hospital visits and deaths annually. The rise of multi-drug resistant bacteria has dramatically increased this burden. Therefore, there is a clinical need to detect and identify bacteria rapidly and accurately in their native state or a culture-free environment. Current diagnostic techniques lack speed and effectiveness in detecting bacteria that are culture-negative, as well as options for in vivo detection. The optical detection of bacteria offers the potential to overcome these obstacles by providing various platforms that can detect bacteria rapidly, with minimum sample preparation, and, in some cases, culture-free directly from patient fluids or even in vivo. These modalities include infrared, Raman, and fluorescence spectroscopy, along with optical coherence tomography, interference, polarization, and laser speckle. However, these techniques are not without their own set of limitations. This review summarizes the strengths and weaknesses of utilizing each of these optical tools for rapid bacteria detection and identification.

Rapid Detection of Botulinum Neurotoxins-A Review

A toxin is a poisonous substance produced within living cells or organisms. One of the most potent groups of toxins currently known are the Botulinum Neurotoxins (BoNTs). These are so deadly that as little as 62 ng could kill an average human; to put this into context that is approximately 200,000 × less than the weight of a grain of sand. The extreme toxicity of BoNTs leads to the need for methods of determining their concentration at very low levels of sensitivity. Currently the mouse bioassay is the most widely used detection method monitoring the activity of the toxin; however, this assay is not only lengthy, it also has both cost and ethical issues due to the use of live animals. This review focuses on detection methods both existing and emerging that remove the need for the use of animals and will look at three areas; speed of detection, sensitivity of detection and finally cost. The assays will have wide reaching interest, ranging from the pharmaceutical/clinical industry for production quality management or as a point of care sensor in suspected cases of botulism, the food industry as a quality control measure, to the military, detecting BoNT that has been potentially used as a bio warfare agent.

Microscale and Nanoscale Electrophotonic Diagnostic Devices

Detecting and identifying infectious agents and potential pathogens in complex environments and characterizing their mode of action is a critical need. Traditional diagnostics have targeted a single characteristic (e.g., spectral response, surface receptor, mass, intrinsic conductivity, etc.). However, advances in detection technologies have identified emerging approaches in which multiple modes of action are combined to obtain enhanced performance characteristics. Particularly appealing in this regard, electrophotonic devices capable of coupling light to electron translocation have experienced rapid recent growth and offer significant advantages for diagnostics. In this review, we explore three specific promising approaches that combine electronics and photonics: (1) assays based on closed bipolar electrochemistry coupling electron transfer to color or fluorescence, (2) sensors based on localized surface plasmon resonances, and (3) emerging nanophotonics approaches, such as those based on zero-mode waveguides and metamaterials.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Highly affine and selective aptamers against cholera toxin as capture elements in magnetic bead-based sandwich ELAA

Aptamers are single-stranded DNA or RNA oligonucleotides, which have been emerging as recognition elements in disease diagnostics and food control, including the detection of bacterial toxins. In this study, we employed the semi-automated just in time-selection to identify aptamers that bind to cholera toxin (CT) with high affinity and specificity. CT is the main virulence factor of Vibrio cholerae and the causative agent of the eponymous disease. For the selected aptamers, dissociation constants in the low nanomolar range (23-56 nM) were determined by fluorescence-based affinity chromatography and cross-reactivity against related proteins was evaluated by direct enzyme-linked aptamer assay (ELAA). Aptamer CT916 has a dissociation constant of 48.5 ± 0.5 nM and shows negligible binding to Shiga-like toxin 1B, protein A and BSA. This aptamer was chosen to develop a sandwich ELAA for the detection of CT from binding buffer and local tap water. Amine-C6- or biotin-modified CT916 was coupled to magnetic beads to serve as the capture element. Using an anti-CT polyclonal antibody as the reporter, detection limits of 2.1 ng/ml in buffer and 2.4 ng/ml in tap water, with a wide log-linear dynamic range from 1 ng/ml to 1000 ng/ml and 500 ng/ml, respectively, were achieved.

Campylobacter spp. detection in the 21st century: a review of the recent achievements in biosensor development

Campylobacter spp. are an important cause of acute bacterial diseases in humans worldwide. Many bacterial species in the Campylobacter genus are considered harmful and may cause several infectious diseases. Currently, there are no commercial biosensors available to detect Campylobacter spp. in food matrices, and little to no testing has been done in research laboratories with actual food matrices. Biosensors potentially provide a powerful means to detect Campylobacter spp. with the advantages of high sensitivity (low limits of detection with a high signal to noise ratio), high specificity (able to selectively detect the target among several similar targets), real time sensing, and in-site monitoring. This review summarizes the latest research in biosensing technologies for detection of Campylobacter spp. based on a variety of transducers and recognition elements. Finally, a comparison is made among all recently reported biosensors for the detection of Campylobacter spp.

Two dimensional barcode-inspired automatic analysis for arrayed microfluidic immunoassays

The usability of many high-throughput lab-on-a-chip devices in point-of-care applications is currently limited by the manual data acquisition and analysis process, which are labor intensive and time consuming. Based on our original design in the biochemical reactions, we proposed here a universal approach to perform automatic, fast, and robust analysis for high-throughput array-based microfluidic immunoassays. Inspired by two-dimensional (2D) barcodes, we incorporated asymmetric function patterns into a microfluidic array. These function patterns provide quantitative information on the characteristic dimensions of the microfluidic array, as well as mark its orientation and origin of coordinates. We used a computer program to perform automatic analysis for a high-throughput antigen/antibody interaction experiment in 10 s, which was more than 500 times faster than conventional manual processing. Our method is broadly applicable to many other microchannel-based immunoassays.

Study of non-covalent interactions of luotonin A derivatives and the DNA minor groove as a first step in the study of their analytical potential as DNA probes

The interaction between DNA and several newly synthesized derivatives of the natural anticancer compound luotonin A has been studied. The results from our work reveal an effective and selective alkaloid/double-stranded DNA (ds-DNA) interaction. In the presence of increasing amounts of ds-DNA, a noticeable fluorescence quenching of the luotonin A derivatives under study was observed. However, this effect did not take place when single-stranded DNA (ss-DNA) was employed. The association constant alkaloids/ds-DNA was calculated by quantitation of such a quenching effect. The influence of other quenchers, namely Co(2+) and Br(-) on the native fluorescence of luotonin A and derivatives was also studied, and a remarkable quenching effect was observed for both ions. We have also investigated how by binding DNA the alkaloids could get protected from the external Co(2+) and Br(-) quenchers. The Stern-Volmer constants (K (SV)) for Co(2+) and Br(-) quenching effect on the studied alkaloids were considerably reduced (10-50%) after incubation of the compounds in the presence of DNA with regard to the K (SV) values in absence of DNA. An increase in the fluorescence anisotropy values of luotonins was also produced only in the presence of ds-DNA but not in the case of ss-DNA. To better characterize the nature of that interaction, viscosimetry assays and ethidium bromide displacement studies were conducted. With regard to DNA reference solutions, the viscosity of solutions containing DNA and luotonin A derivatives was reduced or not significantly increased. It was also observed that the studied compounds were unable to displace the intercalating agent ethidium bromide. All of these results, together with the obtained association constants values (K (ass) = 2.2 × 10(2) - 1.3 × 10(3)), support that neither covalent nor intercalating interactions luotonin A derivatives/ds-DNA are produced, leading to the conclusion that these alkaloids bind ds-DNA through the minor groove. The specific changes in the fluorescence behavior of luotonin A and derivatives distinguishing between ss-DNA and ds-DNA binding, lead us to propose these compounds as attractive turn-off probes to detect DNA hybridization.

Bioaffinity detection of pathogens on surfaces

The demand for improved technologies capable of rapidly detecting pathogens with high sensitivity and selectivity in complex environments continues to be a significant challenge that helps drive the development of new analytical techniques. Surface-based detection platforms are particularly attractive as multiple bioaffinity interactions between different targets and corresponding probe molecules can be monitored simultaneously in a single measurement. Furthermore, the possibilities for developing new signal transduction mechanisms alongside novel signal amplification strategies are much more varied. In this article, we describe some of the latest advances in the use of surface bioaffinity detection of pathogens. Three major sections will be discussed: (i) a brief overview on the choice of probe molecules such as antibodies, proteins and aptamers specific to pathogens and surface attachment chemistries to immobilize those probes onto various substrates, (ii) highlighting examples among the current generation of surface biosensors, and (iii) exploring emerging technologies that are highly promising and likely to form the basis of the next generation of pathogenic sensors.

Sensing the deadliest toxin: technologies for botulinum neurotoxin detection

Sensitive and rapid detection of botulinum neurotoxins (BoNTs), the most poisonous substances known to date, is essential for studies of medical applications of BoNTs and detection of poisoned food, as well as for response to potential bioterrorist threats. Currently, the most common method of BoNT detection is the mouse bioassay. While this assay is sensitive, it is slow, quite expensive, has limited throughput and requires sacrificing animals. Herein, we discuss and compare recently developed alternative in vitro detection methods and assess their ability to supplement or replace the mouse bioassay in the analysis of complex matrix samples.

Sensing the deadliest toxin: technologies for botulinum neurotoxin detection

Sensitive and rapid detection of botulinum neurotoxins (BoNTs), the most poisonous substances known to date, is essential for studies of medical applications of BoNTs and detection of poisoned food, as well as for response to potential bioterrorist threats. Currently, the most common method of BoNT detection is the mouse bioassay. While this assay is sensitive, it is slow, quite expensive, has limited throughput and requires sacrificing animals. Herein, we discuss and compare recently developed alternative in vitro detection methods and assess their ability to supplement or replace the mouse bioassay in the analysis of complex matrix samples.

Trends and Perspectives of Biosensors for Food and Environmental Virology

Food and environmental virology has become a very important and interesting area of research because of food safety and public health concerns. During the last few decades, increasing foodborne diseases and environmental generated illnesses are considered to be highly challenging issues. Biosensor technology holds great promise for the healthcare market, and the security sector. Similar to clinical diagnostic tools, biosensors are being developed for the rapid, reliable, yet inexpensive identification and enumeration of pathogenic viruses which are adulterating environment, food and feed commodities. In this modern era, bio-and nano-technologies play a pivotal role in virological diagnostics of food industry, environmental and veterinary samples. This review covers the recent advances and future prospects of nanotechnology-based bioanalytical microsystems for food and environmental virology.

Fluorescence enhancement of fluorescein isothiocyanate-labeled protein a caused by affinity binding with immunoglobulin g in bovine plasma

Fluorescence enhancement of fluorescein isothiocyanate-labeled protein A (FITC-protein A) caused by the binding with immunoglobulin G (IgG) in bovine plasma was studied. FITC-protein A was immobilized onto a glass surface by covalent bonds. An increase in fluorescence intensity was dependent on IgG concentration ranging from 20 to 78 μg/mL in both phosphate buffer saline and bovine plasma. This method requires no separation procedure, and the reaction time is less than 15 min. A fluorescence enhancement assay by the affinity binding of fluorescence-labeled reagent is thus available for the rapid determination of biomolecules in plasma.

Self-assembled peptide monolayers as a toxin sensing mechanism within arrayed microchannels

A sensor for the lethal bacterial enzyme, botulinum neurotoxin type A (BoNT/A), was developed using self-assembled monolayers (SAMs). SAMs consisting of an immobilized synthetic peptide that mimicked the toxin's in vivo SNAP-25 protein substrate were formed on Au and interfaced with arrayed microfluidic channels. Efforts to optimize SAM composition and assay conditions for greatest reaction efficiency and sensitivity are described in detail. Channel design provided facile fluid manipulation, sample incubation, analyte concentration, and fluorescence detection all within a single microfluidic channel, thus avoiding sample transfer and loss. Peptide SAMs were exposed to varying concentrations of BoNT/A or its catalytic light chain (ALC), resulting in enzymatic cleavage of the peptide substrate from the surface. Fluorescence detection was achieved down to 20 pg/mL ALC and 3 pg/mL BoNT/A in 3 h. Toxin sensing was also accomplished in vegetable soup, demonstrating practicality of the method. The modular design of this microfluidic SAM platform allows for extension to sensing other toxins that operate via enzymatic cleavage, such as the remaining BoNT serotypes B-G, anthrax, and tetanus toxin.

Reduction of Non-Specific Protein Adsorption Using Poly(ethylene) Glycol (PEG) Modified Polyacrylate Hydrogels In Immunoassays for Staphylococcal Enterotoxin B Detection

Three PEG molecules (PEG-methacrylate, -diacrylate and -dimethacrylate) were incorporated into galactose-based polyacrylate hydrogels and their relative abilities to reduce non-specific protein adsorption in immunoassays were determined. Highly crosslinked hydrogels containing amine-terminated functionalities were formed and used to covalently attach antibodies specific for staphylococcal enterotoxin B (SEB). Patterned arrays of immobilized antibodies in the PEG-modified hydrogels were created with a PDMS template containing micro-channels for use in sandwich immunoassays to detect SEB. Different concentrations of the toxin were applied to the hydrogel arrays, followed with a Cy3-labeled tracer antibody specific for the two toxins. Fluorescence laser scanning confocal microscopy of the tracer molecules provided both qualitative and quantitative measurements on the detection sensitivity and the reduction in non-specific binding as a result of PEG incorporation. Results showed the PEG-modified hydrogel significantly reduced non-specific protein binding with a detection limit for SEB of 1 ng/mL. Fluorescence signals showed a 10-fold decrease in the non-specific binding and a 6-fold increase in specific binding of SEB.

Fluoroimmunoassays using the NRL array biosensor

Array-based biosensor technology offers the user the ability to detect and quantify multiple targets in multiple samples simultaneously (Analytical Sciences 23:5-10, 2007). The NRL Array Biosensor has been developed with the aim of creating a system for sensitive, rapid, on-site screening for multiple targets of interest. This system is fluorescence-based, using evanescent illumination of a waveguide, and has demonstrated the use of both sandwich and competitive immunoassays for the detection of both high and low molecular weight targets, respectively. The current portable, automated system has demonstrated detection of a wide variety of analytes ranging from simple chemical compounds to entire bacterial cells, with applications in food safety, disease diagnosis, homeland security and environmental monitoring.

Protein Microarrays for the Detection of Biothreats

Although protein microarrays have proven to be an important tool in proteomics research, the technology is emerging as useful for public health and defense applications. Recent progress in the measurement and characterization of biothreat agents is reviewed in this chapter. Details concerning validation of various protein microarray formats, from contact-printed sandwich assays to supported lipid bilayers, are presented. The reviewed technologies have important implications for in vitro characterization of toxin–ligand interactions, serotyping of bacteria, screening of potential biothreat inhibitors, and as core components of biosensors, among others, research and engineering applications.

Integrating waveguide biosensor

The Integrating Waveguide Biosensor was developed for rapid and sensitive detection of bacterial cells, spores, and toxins. A sandwich format of immunoassay was employed using Salmonella as model. The analyte was immunocaptured on the inner surface of the waveguide and then detected by the antibody conjugated with fluorescent dye. The waveguide was illuminated by an excitation light at a 90 degrees angle. The emitted light from fluorescent labels on the surface of the waveguide was efficiently collected and channeled to a detector at the end of the waveguide, while minimizing interference from the excitation light. Utilizing fluorescent dye Cy5, a 635-nm diode laser for excitation, and a photomultiplier tube detector, the Integrating Waveguide Sensor System was able to detect approximately ten captured cells of Salmonella.

Application of protein arraytubes to bacteria, toxin, and biological warfare agent detection

Microarray technology enables the fast and parallel analysis of a multitude of biologically relevant parameters. Not only nucleic acid-based tests, but also peptide, antigen, and antibody assays using different formats of microarrays evolved within the last decade. They offer the possibility to measure interactions in a miniaturised, economic, automated, and qualitative or quantitative way providing insights into the cellular machinery of diverse organisms. Examples of applications in research and diagnostics are, e.g., O-typing of pathogenic Escherichia coli, detection of bacterial toxins and other biological warfare agents (BW agents) from a variety of different samples, screening of complex antibody libraries, and epitope mapping. Conventional O- and H-serotyping methods can now be substituted by procedures applying DNA oligonucleotide and antibody-based microarrays. For simultaneous and sensitive detection of BW agents microarray-based tests are available, which include not only relevant viruses and bacteria, but also toxins. This application is not only restricted to the security and military sector but it can also be used in the fields of medical diagnostics or public health to detect, e.g., staphylococcal enterotoxins in food or clinical samples. Furthermore, the same technology could be used to detect antibodies against enterotoxins in human sera using a competitive assay. Protein and peptide microarrays can also be used for characterisation of antibodies. On one hand, peptide microarrays allow detailed epitope mapping. On the other hand, a set of different antibodies recognising the same antigen can be spotted as a microarray and labelled as detection antibodies. This approach makes it possible to test every combination, allowing to find the optimal pair of detection/capture antibody.

Automated analytical microarrays: a critical review

Microarrays provide a powerful analytical tool for the simultaneous detection of multiple analytes in a single experiment. The specific affinity reaction of nucleic acids (hybridization) and antibodies towards antigens is the most common bioanalytical method for generating multiplexed quantitative results. Nucleic acid-based analysis is restricted to the detection of cells and viruses. Antibodies are more universal biomolecular receptors that selectively bind small molecules such as pesticides, small toxins, and pharmaceuticals and to biopolymers (e.g. toxins, allergens) and complex biological structures like bacterial cells and viruses. By producing an appropriate antibody, the corresponding antigenic analyte can be detected on a multiplexed immunoanalytical microarray. Food and water analysis along with clinical diagnostics constitute potential application fields for multiplexed analysis. Diverse fluorescence, chemiluminescence, electrochemical, and label-free microarray readout systems have been developed in the last decade. Some of them are constructed as flow-through microarrays by combination with a fluidic system. Microarrays have the potential to become widely accepted as a system for analytical applications, provided that robust and validated results on fully automated platforms are successfully generated. This review gives an overview of the current research on microarrays with the focus on automated systems and quantitative multiplexed applications.

Multiplexed spectroscopic detections

This review describes various platforms used for multiplexed spectroscopic analysis. We highlight the use of different types of spectroscopy for multiplexed detections, including Raman spectroscopy, surface-enhanced Raman spectroscopy, surface plasmon resonance, and fluorescence. This review also explores the use of cross-reactive sensors in combination with pattern-recognition algorithms to monitor multiple analytes in aqueous and vapor matrices. It also discusses applications of these techniques, paying special attention to their use in the detection of biologically relevant analytes.

Antimicrobial Peptides: New Recognition Molecules for Detecting Botulinum Toxins

Many organisms secrete antimicrobial peptides (AMPs) for protection against harmful microbes. The present study describes detection of botulinum neurotoxoids A, B and E using AMPs as recognition elements in an array biosensor. While AMP affinities were similar to those for anti-botulinum antibodies, differences in binding patterns were observed and can potentially be used for identification of toxoid serotype. Furthermore, some AMPs also demonstrated superior detection sensitivity compared to antibodies: toxoid A could be detected at 3.5 LD₅₀ of the active toxin in a 75-min assay, whereas toxoids B and E were detected at 14 and 80 LD₅₀ for their respective toxins.

Real-time monitoring of adhesion and aggregation of platelets using thickness shear mode (TSM) sensor

Hemostasis is required to maintain vascular system integrity, but thrombosis, formation of a clot in a blood vessel, is one of the largest causes of morbidity and mortality in the industrialized world. Novel clinical and research tools for characterizing the hemostatic system are of continued interest, and the object of this research is to test the hypothesis that clinically relevant platelet function can be monitored using an electromechanical sensor. A piezoelectric thickness shear mode (TSM) biosensor coated with collagen-I fibers to promote platelet activation and adhesion was developed and tested for sensitivity to detect these primary events. Magnitude and frequency response of the sensor were monitored under static conditions at 37 degrees C, using platelet-rich plasma (PRP), and PRP with adenosine diphosphate (ADP), a clinical aggregation inhibitor (abciximab), or a collagen binding inhibitor. Sensors loaded with PRP exhibited a 3-stage response; no significant change in response for the first 20 min (Stage-1), followed by a larger drop in response (Stage-2) and subsequently, response gradually increased (Stage-3). Exogenous ADP stimulated an immediate Stage-2 response, while abciximab delayed and reduced the magnitude change of Stage-2. In the presence of collagen inhibitor, Stage-2 response was similar to that of control but was delayed by an additional 20 min. The obtained results, supported by epifluorescence and complementary SEM studies, demonstrated the selective sensitivity of TSM electromechanical biosensors to monitor platelet function and inhibition, particularly aggregation.

Development of automated amperometric detection of antibodies against Bacillus anthracis protective antigen

Picogram levels of antibodies against the protective antigen (PA) of Bacillus anthracis were detected in an automated electrochemical sandwich-type enzyme-linked immunosorbant assay. The antibodies were captured and detected using an 8 x 3 array of 50-microm-diameter cavities. The reagent and sample volumes were as low as 200 nL in a less than 25-min assay from capture to signal generation. The electrochemical detection of the antibodies was demonstrated at 0.05-10 microg/mL containing only 10-5,000 pg antibodies. The limit of detection is 10 fg for a 200-nL sample. Detection of anti-PA immunoglobulin G performed in spiked normal human serum and fresh whole human blood did not show a significant difference from detection in a buffer. The initial automation of the assay involved the use of a digital syringe pump for the delivery of reagents to the capture surface.

Advantages and limitations of on-line solid phase extraction coupled to liquid chromatography–mass spectrometry technologies versus biosensors for monitoring of emerging contaminants in water

On-line solid phase extraction (SPE) coupled to liquid chromatography-mass spectrometry (LC-MS) and biosensors are advanced technologies that have found increasing application in the analysis of environmental contaminants although their application to the determination of emerging contaminants (previously unknown or unrecognized pollutants) has been still limited. This review covers the most recent advances occurred in the areas of on-line SPE-LC-MS and biosensors, discusses and compares the main strengths and limitations of the two approaches, and examines their most relevant applications to the analysis of emerging contaminants in environmental waters. So far, the on-line configuration most frequently used has been SPE coupled to liquid chromatography-(tandem) mass spectrometry. Sorbents used for on-line SPE have included both traditional (alkyl-bonded silicas and polymers) and novel (restricted access materials (RAMs), molecularly imprinted synthetic polymers (MIPs), and immobilized receptors or antibodies (immunosorbents) materials. The biosensor technologies most frequently applied have been based on the use of antibodies and, to a lesser extent, enzymes, bacteria, receptors and DNA as recognition elements, and the use of optical and electrochemical transducing elements. Emerging contaminants investigated by means of these two techniques have included pharmaceuticals, endocrine disrupting compounds such as estrogens, alkylphenols and bisphenol A, pesticides transformation products, disinfection by-products, and bacterial toxins and mycotoxins, among others. Both techniques offer advantageous, and frequently comparable, features such as high sensitivity and selectivity, minimum sample manipulation, and automation. Biosensors are, in addition, relatively cheap and fast, which make them ideally suited for routine testing and screening of samples; however, in most cases, they can not compete yet with on-line SPE procedures in terms of accuracy, reproducibility, reliability (confirmation) of results, and capacity for multi-analyte determination.

Array biosensor based on enzyme kinetics monitoring by fluorescence spectroscopy: Application for neurotoxins detection

The aim of the present work is to develop an evanescence wave array biosensor exploiting the "kinetic" approach of enzymatic reaction and further detection of the reaction products via pH sensitive fluorophore reporter. To demonstrate the feasibility of this approach, we have developed a biosensor array with the potential for direct detection of organophosphates using as a biorecognition element, an enzyme organophosphorus hydrolase (OPH), conjugated with a pH-sensitive fluorophore, carboxynaphthofluorescein (CNF). The presence of reference spots allows the discrimination of the enzymatic and non-enzymatic based pH changes; bovine serum albumin (BSA) was used as a non-enzymatic scaffold protein for CNF attachment at the reference spots. An array biosensor unit developed at the Naval Research Laboratories (NRL) was adopted as the detection platform and appropriately modified for enzyme-based measurements. A planar multi-mode waveguide was covered with an optically transparent TiO(2) layer to increase the surface area available for immobilization. The biosensor enabled the detection of 2.5 microM paraoxon, and 10 microM DFP and parathion, respectively. Very short response time of 30s can be achieved with a total analysis time of less than 2 min. When operated at room temperature and stored at 4 degrees C, the waveguide retained reasonable activity for greater than 45 days.

Leveraging protein purification strategies in proteomics

The proteomic studies, although, tend to be analytical in nature, yet many strategies of preparative protein purification can be usefully employed in such studies. This review points out the importance of purification techniques which are capable of dealing with samples which are suspensions rather than clear solution, e.g. aqueous two phase partitioning, three phase partitioning, expanded bed chromatography, etc. The review also outlines the potential of non-chromatographic techniques in dealing with fractionation of proteomes. Separation protocols which can deal with post-translationally modified (PTM) proteins are also considered.

The array biosensor: portable, automated systems

With recent advances in surface chemistry, microfluidics, and data analysis, there are ever increasing reports of array-based methods for detecting and quantifying multiple targets. However, only a few systems have been described that require minimal preparation of complex samples and possess a means of quantitatively assessing matrix effects. The NRL Array Biosensor has been developed with the goal of rapid and sensitive detection of multiple targets from multiple samples analyzed simultaneously. A key characteristic of this system is its two-dimensional configuration, which allows controls and standards to be analyzed in parallel with unknowns. Although the majority of our work has focused on instrument automation and immunoassay development, we have recently initiated efforts to utilize alternative recognition molecules, such as peptides and sugars, for detection of a wider variety of targets. The array biosensor has demonstrated utility for a variety of applications, including food safety, disease diagnosis, monitoring immune response, and homeland security, and is presently being transitioned to the commercial sector for manufacturing.

Automated 10-channel capillary chip immunodetector for biological agents detection

The automated 10-channel capillary chip immunodetector (10K-IDWG) is a prototype, which has been developed for automatically operated biological agents (BA) point detection. The current technology uses a chemiluminescence capillary immunoassay (EIA) technique in combination with integrated microfluidics and allows the highly sensitive and rapid detection and preliminary identification of multiple BA in aqueous solutions in the laboratory. The chemiluminescence capillary EIA are performed within a disposable capillary chip containing 10 fused-silica capillaries arranged in parallel coated with selected capture antibodies. A multianode-photomultiplier array is used to detect chemiluminescence intensity in each capillary. Reservoirs for reagents and buffers and a waste disposal reservoir are integrated. This paper describes the technology of the 10K-IDWG and its evaluation with three different BA, the toxin staphylococcal enterotoxin B (SEB), the bacterial analyte Escherichia coli (E. coli) O157:H7 as a model for bacterial pathogens, and the bacteriophage M13 as a model for virus pathogens. The 10K-IDWG is able to detect the above mentioned three BA in an aqueous sample within 29 min (single analyte-detection and multiplexing). Limits of detection (LOD) are 0.1 ng/ml for SEB, 10(4)cfu/ml for E. coli O157:H7, and 5x10(5) pfu/ml for M13. Cross reactivities between the three assays were not observed.

Trends in detection of warfare agents. Detection methods for ricin, staphylococcal enterotoxin B and T-2 toxin

An overview of the different detection methods available for ricin, staphylococcal enterotoxin B (SEB) and T-2 toxin is presented here. These toxins are potential biological warfare agents (BWA). The aim of this review is not to cover all the papers that had been published but rather to give an overall picture of the trend in the detection methodologies for potential biological warfare agents as we do see the emerging threats from these three toxins. The advantages and disadvantages of each methodology as well as the detection limit will be reviewed. It seems that mass spectrometry has created a niche for analysis of proteinaceous toxins, ricin and SEB as well as molecular toxin, T-2 toxin given its high sensitivity, high selectivity, high specificity and capability to identify and quantify unknown agents simultaneously in a short time frame. But its main drawbacks are its sophisticated instrumentation and its high cost. Improvised immunoassay may be an alternative.