Autonomous Detection of Aerosolized Biological Agents by Multiplexed Immunoassay with Polymerase Chain Reaction Confirmation

Lab-on-a-chip technology for in situ combined observations in oceanography

The oceans sustain the global environment and diverse ecosystems through a variety of biogeochemical processes and their complex interactions. In order to understand the dynamism of the local or global marine environments, multimodal combined observations must be carried out in situ. On the other hand, instrumentation of in situ measurement techniques enabling biological and/or biochemical combined observations is challenging in aquatic environments, including the ocean, because biochemical flow analyses require a more complex configuration than physicochemical electrode sensors. Despite this technical hurdle, in situ analyzers have been developed to measure the concentrations of seawater contents such as nutrients, trace metals, and biological components. These technologies have been used for cutting-edge ocean observations to elucidate the biogeochemical properties of water mass with a high spatiotemporal resolution. In this context, the contribution of lab-on-a-chip (LoC) technology toward the miniaturization and functional integration of in situ analyzers has been gaining momentum. Due to their mountability, in situ LoC technologies provide ideal instrumentation for underwater analyzers, especially for miniaturized underwater observation platforms. Consequently, the appropriate combination of reliable LoC and underwater technologies is essential to realize practical in situ LoC analyzers suitable for underwater environments, including the deep sea. Moreover, the development of fundamental LoC technologies for underwater analyzers, which operate stably in extreme environments, should also contribute to in situ measurements for public or industrial purposes in harsh environments as well as the exploration of the extraterrestrial frontier.

Bioaerosol Sampling: Classical Approaches, Advances, and Perspectives

Bioaerosol sampling is an essential and integral part of any bioaerosol investigation. Since bioaerosols are very diverse in terms of their sizes, species, biological properties, and requirements for their detection and quantification, bioaerosol sampling is an active, yet challenging research area. This paper was inspired by the discussions during the 2018 International Aerosol Conference (IAC) (St. Louis, MO) regarding the need to summarize the current state of the art in bioaerosol research, including bioaerosol sampling, and the need to develop a more standardized set of guidelines for protocols used in bioaerosol research. The manuscript is a combination of literature review and perspectives: it discusses the main bioaerosol sampling techniques and then overviews the latest technical developments in each area; the overview is followed by the discussion of the emerging trends and developments in the field, including personal sampling, application of passive samplers, and advances toward improving bioaerosol detection limits as well as the emerging challenges such as collection of viruses and collection of unbiased samples for bioaerosol sequencing. The paper also discusses some of the practical aspects of bioaerosol sampling with particular focus on sampling aspects that could lead to bioaerosol determination bias. The manuscript concludes by suggesting several goals for bioaerosol sampling and development community to work towards and describes some of the grand bioaerosol challenges discussed at the IAC 2018.

Identification of microbial key-indicators of oil contamination at sea through tracking of oil biotransformation: An Arctic field and laboratory study

In this paper, a molecular analytical approach for detecting hydrocarbonoclastic bacteria in water is suggested as a proxy measurement for tracking petroleum discharges in industrialized or pristine aquatic environments. This approach is tested for general application in cold marine regions (freezing to 5 °C). We used amplicon sequencing and qPCR to quantify 16S rRNA and GyrB genes from oleophilic bacteria in seawater samples from two different crude oil enrichments. The first experiment was conducted in a controlled environment using laboratory conditions and natural North Sea fjord seawater (NSC) at a constant temperature of 5 °C. The second was performed in the field with natural Arctic seawater (ARC) and outdoor temperature conditions from -7 °C to around 4 °C. Although the experimental conditions for NSC and ARC differed, the temporal changes in bacterial communities were comparable and reflected oil biotransformation processes. The common bacterial OTUs for NSC and ARC had the highest identity to Colwellia rossensis and Oleispira antarctica rRNA sequences and were enriched within a few days in both conditions. Other typical oil degrading bacteria such as Alcanivorax (n-alkane degrader) and Cycloclasticus (polycyclic aromatic hydrocarbons degrader) were rapidly enriched only in NSC conditions. Both the strong correlation between Oleispira SSU gene copies and oil concentration, and the specificity of the Oleispira assay suggest that this organism is a robust bioindicator for seawater contaminated by petroleum in cold water environments. Further optimization for automation of the Oleispira assay for in situ analysis with a genosensing device is underway. The assay for Colwellia quantification requires more specificity to fewer Colwellia OTUs and a well-established dose-response relationship before those taxa are used for oil tracking purposes.

Integrated micro-optofluidic platform for real-time detection of airborne microorganisms

We demonstrate an integrated micro-optofluidic platform for real-time, continuous detection and quantification of airborne microorganisms. Measurements of the fluorescence and light scattering from single particles in a microfluidic channel are used to determine the total particle number concentration and the microorganism number concentration in real-time. The system performance is examined by evaluating standard particle measurements with various sample flow rates and the ratios of fluorescent to non-fluorescent particles. To apply this method to real-time detection of airborne microorganisms, airborne Escherichia coli, Bacillus subtilis, and Staphylococcus epidermidis cells were introduced into the micro-optofluidic platform via bioaerosol generation, and a liquid-type particle collection setup was used. We demonstrate successful discrimination of SYTO82-dyed fluorescent bacterial cells from other residue particles in a continuous and real-time manner. In comparison with traditional microscopy cell counting and colony culture methods, this micro-optofluidic platform is not only more accurate in terms of the detection efficiency for airborne microorganisms but it also provides additional information on the total particle number concentration.

Efficiency of Airborne Sample Analysis Platform (ASAP) bioaerosol sampler for pathogen detection

The threat of bioterrorism and pandemics has highlighted the urgency for rapid and reliable bioaerosol detection in different environments. Safeguarding against such threats requires continuous sampling of the ambient air for pathogen detection. In this study we investigated the efficacy of the Airborne Sample Analysis Platform (ASAP) 2800 bioaerosol sampler to collect representative samples of air and identify specific viruses suspended as bioaerosols. To test this concept, we aerosolized an innocuous replication-defective bovine adenovirus serotype 3 (BAdV3) in a controlled laboratory environment. The ASAP efficiently trapped the surrogate virus at 5 × 10³ plaque-forming units (p.f.u.) [2 × 10⁵ genome copy equivalent] concentrations or more resulting in the successful detection of the virus using quantitative PCR. These results support the further development of ASAP for bioaerosol pathogen detection.

The rotary zone thermal cycler: a low-power system enabling automated rapid PCR

Advances in molecular biology, microfluidics, and laboratory automation continue to expand the accessibility and applicability of these methods beyond the confines of conventional, centralized laboratory facilities and into point of use roles in clinical, military, forensic, and field-deployed applications. As a result, there is a growing need to adapt the unit operations of molecular biology (e.g., aliquoting, centrifuging, mixing, and thermal cycling) to compact, portable, low-power, and automation-ready formats. Here we present one such adaptation, the rotary zone thermal cycler (RZTC), a novel wheel-based device capable of cycling up to four different fixed-temperature blocks into contact with a stationary 4-microliter capillary-bound sample to realize 1-3 second transitions with steady state heater power of less than 10 W. We demonstrate the utility of the RZTC for DNA amplification as part of a highly integrated rotary zone PCR (rzPCR) system that uses low-volume valves and syringe-based fluid handling to automate sample loading and unloading, thermal cycling, and between-run cleaning functionalities in a compact, modular form factor. In addition to characterizing the performance of the RZTC and the efficacy of different online cleaning protocols, we present preliminary results for rapid single-plex PCR, multiplex short tandem repeat (STR) amplification, and second strand cDNA synthesis.

Quantitative and sensitive RNA based detection of Bacillus spores

The fast and reliable detection of bacterial spores is of great importance and still remains a challenge. Here we describe a direct RNA-based diagnostic method for the specific detection of viable bacterial spores which does not depends on an enzymatic amplification step and therefore is directly appropriate for quantification. The procedure includes the following steps: (i) heat activation of spores, (ii) germination and enrichment cultivation, (iii) cell lysis, and (iv) analysis of 16S rRNA in crude cell lysates using a sandwich hybridization assay. The sensitivity of the method is dependent on the cultivation time and the detection limit; it is possible to detect 10 spores per ml when the RNA analysis is performed after 6 h of enrichment cultivation. At spore concentrations above 10(6) spores per ml the cultivation time can be shortened to 30 min. Total analysis times are in the range of 2-8 h depending on the spore concentration in samples. The developed procedure is optimized at the example of Bacillus subtilis spores but should be applicable to other organisms. The new method can easily be modified for other target RNAs and is suitable for specific detection of spores from known groups of organisms.

Real-time detection of an airborne microorganism using inertial impaction and mini-fluorescent microscopy

To achieve successful real-time detection of airborne pathogenic microorganisms, the problem must be considered in terms of their physical size and biological characteristics. We developed an airborne microorganism detection chip to realize the detection of microorganisms, ensuring compactness, sensitivity, cost-efficiency, and portability, using three key components: an inertial impaction system, a cartridge-type impaction plate, and a mini-fluorescent microscope. The inertial impaction system was used to separate microorganisms in terms of their aerodynamic particle size, and was fabricated with three impaction stages. Numerical analysis was performed to design the system; the calculated cutoff diameter at each impaction stage was 2.02 (first stage), 0.88 (second stage), and 0.54 μm (third stage). The measured cutoff diameters were 2.24, 0.91, and 0.49 μm, respectively. A cartridge-type impaction plate was used, composed of molded polydimethylsiloxane (PDMS) and an actual impaction region made of a SYBR green I dye-stained agar plate. A mini-fluorescent microscope was used to distinguish microbes from non-biological particles. Images of the microorganisms deposited at the impaction zone were obtained via mini-fluorescent microscopy, and fluorescent intensities of the images were calculated using in-house image-processing software. The results showed that the developed system successfully identified aerosolized biological particles from non-biological particles in real time.

Evaluation of the FilmArray® system for detection of Bacillus anthracis, Francisella tularensis and Yersinia pestis

Aims

To evaluate the sensitivity and specificity of the BioFire Diagnostics FilmArray® system in combination with their Biothreat Panel for the detection of Bacillus anthracis (Ba), Francisella tularensis (Ft) and Yersinia pestis (Yp) DNA, and demonstrate the detection of Ba spores.

Methods and Results

DNA samples from Ba, Ft and Yp strains and near-neighbours, and live Ba spores were analysed using the FilmArray® Biothreat Panel, a multiplexed PCR-based assay for 17 pathogens and toxins. Sensitivity studies with DNA indicate that the limit of detection is 250 genome equivalents (GEs) per sample or lower. Furthermore, the identification of Ft, Yp or Bacillus species was made in 63 of 72 samples tested at 25 GE or less. With samples containing 25 CFU of Ba Sterne spores, at least one of the two possible Ba markers was identified in all samples tested. We observed no cross-reactivity with near-neighbour DNAs.

Conclusions

Our results indicate that the FilmArray® Biothreat Panel is a sensitive and selective assay for detecting the genetic signatures of Ba, Ft and Yp.

Significance and Impact of the Study

The FilmArray® platform is a complete sample-to-answer system, combining sample preparation, PCR and data analysis. This system is particularly suited for biothreat testing where samples need to be analysed for multiple biothreats by operators with limited training.

Bubble-induced damping in displacement-driven microfluidic flows

Bubble damping in displacement-driven microfluidic flows was theoretically and experimentally investigated for a Y-channel microfluidic network. The system was found to exhibit linear behavior for typical microfluidic flow conditions. The bubbles induced a low-pass filter behavior with a characteristic cutoff frequency that scaled proportionally with flow rate and inversely with bubble volume and exhibited a minimum with respect to the relative resistances of the connecting channels. A theoretical model based on the electrical circuit analogy was able to predict experimentally observed damping of fluctuations with excellent agreement. Finally, a flowmeter with high resolution (0.01 μL/min) was demonstrated as an application of the bubble-aided stabilization. This study may aid in the design of many other bubble-stabilized microfluidic systems.

Underwater application of quantitative PCR on an ocean mooring

The Environmental Sample Processor (ESP) is a device that allows for the underwater, autonomous application of DNA and protein probe array technologies as a means to remotely identify and quantify, in situ, marine microorganisms and substances they produce. Here, we added functionality to the ESP through the development and incorporation of a module capable of solid-phase nucleic acid extraction and quantitative PCR (qPCR). Samples collected by the instrument were homogenized in a chaotropic buffer compatible with direct detection of ribosomal RNA (rRNA) and nucleic acid purification. From a single sample, both an rRNA community profile and select gene abundances were ascertained. To illustrate this functionality, we focused on bacterioplankton commonly found along the central coast of California and that are known to vary in accordance with different oceanic conditions. DNA probe arrays targeting rRNA revealed the presence of 16S rRNA indicative of marine crenarchaea, SAR11 and marine cyanobacteria; in parallel, qPCR was used to detect 16S rRNA genes from the former two groups and the large subunit RuBisCo gene (rbcL) from Synecchococcus. The PCR-enabled ESP was deployed on a coastal mooring in Monterey Bay for 28 days during the spring-summer upwelling season. The distributions of the targeted bacterioplankon groups were as expected, with the exception of an increase in abundance of marine crenarchaea in anomalous nitrate-rich, low-salinity waters. The unexpected co-occurrence demonstrated the utility of the ESP in detecting novel events relative to previously described distributions of particular bacterioplankton groups. The ESP can easily be configured to detect and enumerate genes and gene products from a wide range of organisms. This study demonstrated for the first time that gene abundances could be assessed autonomously, underwater in near real-time and referenced against prevailing chemical, physical and bulk biological conditions.

Pathogen detection using a liquid array technology

Low concentrations of microbial pathogens in pure and mixed samples were detected using a bead-based, liquid array technology. A 20-bp sequence in the 23S rRNA gene, rrl, was amplified in four microorganisms: Bacillus cereus, Escherichia coli, Salmonella enterica and Staphylococcus aureus. PCR products were positively identified with the Luminex(®) 100™ system. The system could detect very low amounts of DNA and the instrument response was proportional to the input concentration. The lower limit of detection (LLD) was determined to be 0.5 ng for B. cereus and E. coli and 2 ng for S. enterica. The LLD for S. aureus was not determined as the instrument response was still above the threshold when quantities of DNA as low as 0.25 ng were used. The platform positively identified organisms present in mixed samples even when the minor component was overshadowed by a 10-fold excess of the major component.

Identifying experimental surrogates for Bacillus anthracis spores: a review

Bacillus anthracis, the causative agent of anthrax, is a proven biological weapon. In order to study this threat, a number of experimental surrogates have been used over the past 70 years. However, not all surrogates are appropriate for B. anthracis, especially when investigating transport, fate and survival. Although B. atrophaeus has been widely used as a B. anthracis surrogate, the two species do not always behave identically in transport and survival models. Therefore, we devised a scheme to identify a more appropriate surrogate for B. anthracis. Our selection criteria included risk of use (pathogenicity), phylogenetic relationship, morphology and comparative survivability when challenged with biocides. Although our knowledge of certain parameters remains incomplete, especially with regards to comparisons of spore longevity under natural conditions, we found that B. thuringiensis provided the best overall fit as a non-pathogenic surrogate for B. anthracis. Thus, we suggest focusing on this surrogate in future experiments of spore fate and transport modelling.

A sample-in-answer-out instrument for the detection of multiple respiratory pathogens in unprepared nasopharyngeal swab samples

Multiplex RT-PCR suspension array assays provide a powerful tool for identifying the causative agent(s) of respiratory infections. These assays are time consuming and laborious on a time-per-sample basis if only a few samples require processing. To address this shortcoming and provide an automated solution for fast detection and identification of viral pathogens, we developed the first automated multiplex RT-PCR suspension array instrument capable of handling unprepared clinical samples. The instrument requires less than 3 minutes of hands-on time for a result generated in approximately 2.5 hours. In analytical studies, the instrument performed as well as manually performed assays. The performance of the instrument and loaded multiplex viral detection assay was then tested using unprepared nasopharyngeal samples. The instrument-performed assay detected 61 of 71 RSV positive samples, for a sensitivity of 85.9%. Adenovirus (n = 5) and influenza B (n = 3) were less prevalent in the sample set, but detected to similar levels, 80% and 75%, respectively. The same sample set was also tested using FDA approved immuno-assay rapid tests, and the instrument was found to be more sensitive than the rapid tests with the sole exception being influenza A (n = 16), which was poorly detected due to significant sequence mismatches between the influenza A primer/probe set included in the multiplex mixture and the circulating influenza A strains. Overall, these data demonstrate the developed prototype platform performs multiplex array assays as well as hand-performed assays, and that the instrument's sensitivity and specificity are dictated by the quality of the loaded multiplex assay.

Array lead zirconate titanate/glass piezoelectric microcantilevers for real-time detection of Bacillus anthracis with 10 spores/ml sensitivity and 1/1000 selectivity in bacterial mixtures

An array of three identical piezoelectric microcantilever sensors (PEMSs) consisting of a lead zirconate titanate layer bonded to a glass layer was fabricated and examined for simultaneous, in situ, real-time, all-electrical detection of Bacillus anthracis (BA) spores in an aqueous suspension using the first longitudinal extension mode of resonance. With anti-BA antibody immobilized on the sensor surfaces all three PEMS exhibited identical BA detection resonance frequency shifts at all tested concentrations, 10-10(7) spores/ml with a standard deviation of less than 10%. The detection concentration limit of 10 spores/ml was about two orders of magnitude lower than would be permitted by flexural peaks. In blinded-sample testing, the array PEMS detected BA in three samples containing BA: (1) 3.3x10(3) spores/ml, (2) a mixture of 3.3x10(3) spores/ml and 3.3x10(5) S. aureus (SA) and P. aeruginosa (PA) per ml, and (3) a mixture of 3.3x10(3) spores/ml with 3.3x10(6) SA+PA/ml. There was no response to a sample containing only 3.3x10(6) SA+PA/ml. These results illustrate the sensitivity, specificity, reusability, and reliability of array PEMS for in situ, real-time detection of BA spores.

Simultaneous quantification of five bacterial and plant toxins from complex matrices using a multiplexed fluorescent magnetic suspension assay

Proteotoxins such as ricin, abrin, botulinum neurotoxins type A and B (BoNT/A, BoNT/B) and staphylococcal enterotoxin B (SEB) are regarded as potential biological warfare agents which could be used for bioterrorism attacks on the food chain. In this study we used a novel immunisation strategy to generate high-affinity monoclonal and polyclonal antibodies against native ricin, BoNT/A, and BoNT/B. The antibodies were used along with antibodies against SEB and abrin to establish a highly sensitive magnetic and fluorescent multiplex bead array with excellent sensitivities between 2 ng/L and 546 ng/L from a minimal sample volume of 50 microL. The assay was validated using 20 different related analytes and the assay precision was determined. Advancing the existing bead array technology, the novel magnetic and fluorescent microbeads proved amenable to enrichment procedures, by further increasing sensitivity to 0.3-85 ng/L, starting from a sample volume of 500 microL. Furthermore, the method was successfully applied for the simultaneous identification of the target toxins spiked into complex food matrices like milk, baby food and yoghurt. On the basis of our results, the assay appears to be a good tool for large-scale screening of samples from the food supply chain.

Flow Cytometry: A Multipurpose Technology for a Wide Spectrum of Global Biosecurity Applications

Flow cytometry, and its offspring-flow sorting, are extremely useful technologies for biosecurity and public health studies related to infectious disease. Applications range from environmental surveillance of pathogens to diagnosis and the development of vaccines and therapeutics for prevention and control of infectious diseases. Flow cytometers have been developed for laboratory analysis and field deployment. The current state of the art could enjoy more widespread use if instruments and data analysis were made simpler and had more automated functions, and if technology was modified to reduce biosafety concerns related to analysis and sorting of infectious organisms. The full spectrum of possible applications of flow cytometry technology to global biosecurity challenges has not yet been realized.

Thermostable llama single domain antibodies for detection of botulinum A neurotoxin complex

Immunoglobulins from animals of the Camelidae family boast unique forms that do not incorporate light chains. Antigen binding in these unconventional heavy-chain homodimers is mediated through a single variable domain. When expressed recombinantly these variable domains are termed single domain antibodies (sdAb) and are among the smallest naturally IgG-derived antigen binding units. SdAb possess good solubility, thermostability, and can refold after heat and chemical denaturation making them promising alternative recognition elements. We have constructed a library of phage-displayed sdAb from a llama immunized with a cocktail of botulinum neurotoxin (BoNT) complex toxoids and panned the library for binders for BoNT A complex toxoid. Six unique binders were isolated and found to specifically bind BoNT A complex in toxoid and untoxoided forms and when used in optimal combinations in buffer and milk could detect 100 pg/mL untoxoided complex. All sdAb retained their ability to specifically bind target after heating to 85 degrees C for 1 h, in contrast to conventional polyclonal sera. All of the sdAb were highly specific for subtype A1 rather than A2 and demonstrated binding to the 33 kDa hemagglutinin, potentially to a somewhat overlapping linear epitope. The unique properties of these sdAb may provide advantages for many diagnostic applications where long-term storage and in-line monitoring require very rugged yet highly specific recognition elements.

Quantification of magnetic susceptibility in several strains of Bacillus spores: implications for separation and detection

Three strains of Bacillus: Bacillus atrophaeus (formally Bacillus globigii), Bacillus thuringiensis, and Bacillus cereus were tested for their intrinsic magnetic susceptibility. All three strains when sporulated demonstrated significant magnetic susceptibility using an instrument referred to as Cell Tracking Velocimetry. Energy dispersive spectroscopy also confirmed the presence of paramagnetic elements, Fe and Mn, in the spore form of the bacteria. It was demonstrated that this magnetic susceptibility is sufficient to separate and deposit these spores on glass slides in a magnetic deposition system. These results indicate the potential to separate spores with intrinsic magnetic susceptibility directly out of water or air samples.

Autonomous Microfluidic Sample Preparation System for Protein Profile-Based Detection of Aerosolized Bacterial Cells and Spores

For domestic and military security, an autonomous system capable of continuously monitoring for airborne biothreat agents is necessary. At present, no system meets the requirements for size, speed, sensitivity, and selectivity to warn against and lead to the prevention of infection in field settings. We present a fully automated system for the detection of aerosolized bacterial biothreat agents such as Bacillus subtilis (surrogate for Bacillus anthracis) based on protein profiling by chip gel electrophoresis coupled with a microfluidic sample preparation system. Protein profiling has previously been demonstrated to differentiate between bacterial organisms. With the goal of reducing response time, multiple microfluidic component modules, including aerosol collection via a commercially available collector, concentration, thermochemical lysis, size exclusion chromatography, fluorescent labeling, and chip gel electrophoresis were integrated together to create an autonomous collection/sample preparation/analysis system. The cycle time for sample preparation was approximately 5 min, while total cycle time, including chip gel electrophoresis, was approximately 10 min. Sensitivity of the coupled system for the detection of B. subtilis spores was 16 agent-containing particles per liter of air, based on samples that were prepared to simulate those collected by wetted cyclone aerosol collector of approximately 80% efficiency operating for 7 min.

Raman Chemical Imaging Spectroscopy Reagentless Detection and Identification of Pathogens: Signature Development and Evaluation

An optical detection method, Raman chemical imaging spectroscopy (RCIS), is reported, which combines Raman spectroscopy, fluorescence spectroscopy, and digital imaging. Using this method, trace levels of biothreat organisms are detected in the presence of complex environmental backgrounds without the use of amplification or enhancement techniques. RCIS is reliant upon the use of Raman signatures and automated recognition algorithms to perform species-level identification. The rationale and steps for constructing a pathogen Raman signature library are described, as well as the first reported Raman spectra from live, priority pathogens, including Bacillus anthracis, Yersinia pestis, Burkholderia mallei, Francisella tularensis, Brucella abortus, and ricin. Results from a government-managed blind trial evaluation of the signature library demonstrated excellent specificity under controlled laboratory conditions.

Heightened sense for sensing: recent advances in pathogen immunoassay sensing platforms

Rapid and efficient sensors are essential for effective defense against the emerging threat of bioterrorism and biological warfare. This review article describes several recent immunosensing advances that are relevant to biothreat detection. These highly diverse examples are intended to demonstrate the breadth of these immunochemical sensing systems and platforms while highlighting those technologies that are suitable for pathogen detection.

Magnetic biosensor for the detection of Yersinia pestis

A novel type of magnetic-beads based magnetic biosensor is described for the detection of Yersinia pestis. Experiments were performed with the antigen fraction F1 of these bacteria. The magnetic sensor platform offers easy and reliable detection of Y. pestis by the use of magnetic beads for labelling and quantification in a single step due to their paramagnetic features. The system uses antiYPF1 antibodies as capture element on ABICAP columns as core element of the magnetic sensor. Several immobilization methods for antibodies on polyethylene were exploited. The established biosensor has a linear detection range of 25-300 ng/ml Y. pestis antigen F1 and a detection limit of 2.5 ng/ml in buffer and human blood serum. The presented sensor system is small, simple, portable and therefore usable as off-lab detection unit for medical and warfare analytes.

Facile generation of heat-stable antiviral and antitoxin single domain antibodies from a semisynthetic llama library

Llamas possess a class of unconventional immunoglobulins that have only heavy chains; unpaired heavy variable domains are responsible for antigen binding. These domains have previously been cloned and expressed as single domain antibodies (sdAbs); they comprise the smallest known antigen binding fragments. SdAbs have been shown to bind antigens at >90 degrees C and to refold after being denatured. To take advantage of the remarkable properties of sdAbs, we constructed a large, semisynthetic llama sdAb library. This library facilitated the rapid selection of binders to an array of biothreat targets. We selected sdAb specific for live vaccinia virus (a smallpox virus surrogate), hen egg lysozyme, cholera toxin, ricin, and staphylococcal enterotoxin B. The selected sdAb possessed high specificity as well as enhanced thermal stability in comparison to conventional IgG and scFv antibodies. We also determined equilibrium dissociation constants as well as demonstrated the use of several antitoxin sdAbs as effective capture and reporter molecules in sandwich assays on the Luminex instrument. The ability to rapidly select such rugged antibodies will enhance the reliability of immunoassays by extending shelf life and the capacity to function in hostile environments.

Current methods for the rapid diagnosis of bioterrorism-related infectious agents

Bioterrorism is the calculated use of violence against civilians to attain political, religious, or ideologic goals using weapons of biological warfare. Bioterrorism is of particular concern because these weapons can be manufactured with ease and do not require highly sophisticated technology. Moreover, biologic agents can be delivered and spread easily and can effect a large population and geographic area. The terrorist attacks occurring around the world necessitate society's continued investment in adequate defense against these unpredictable and irrational events.

Bacillus anthracis: toxicology, epidemiology and current rapid-detection methods

B. anthracis, the causative agent for anthrax, has been well studied for over 150 years. Due to the genetic similarities among various Bacillus species, as well as its existence in both a spore form and a vegetative state, the detection and specific identification of B. anthracis have been proven to require complex techniques and/or laborious methods. With the heightened interest in the organism as a potential biological threat agent, a large number of interesting detection technologies have recently been developed, including methods involving immunological and nucleic acid-based assay formats. The technologies range from culture-based methods to portable Total Analysis Systems based on real-time PCR. This review with 170 references provides a brief background on the toxicology and epidemiology of B. anthracis, discusses challenges associated with its detection related to genetic similarities to other species, and reviews immunological and, with greater emphasis, nucleic acid-based detection systems.

Current and developing technologies for monitoring agents of bioterrorism and biowarfare

Recent events have made public health officials acutely aware of the importance of rapidly and accurately detecting acts of bioterrorism. Because bioterrorism is difficult to predict or prevent, reliable platforms to rapidly detect and identify biothreat agents are important to minimize the spread of these agents and to protect the public health. These platforms must not only be sensitive and specific, but must also be able to accurately detect a variety of pathogens, including modified or previously uncharacterized agents, directly from complex sample matrices. Various commercial tests utilizing biochemical, immunological, nucleic acid, and bioluminescence procedures are currently available to identify biological threat agents. Newer tests have also been developed to identify such agents using aptamers, biochips, evanescent wave biosensors, cantilevers, living cells, and other innovative technologies. This review describes these current and developing technologies and considers challenges to rapid, accurate detection of biothreat agents. Although there is no ideal platform, many of these technologies have proved invaluable for the detection and identification of biothreat agents.