Microchip devices for detecting terrorist weapons

Application of microfluidic technologies in forensic analysis

The application of microfluidic technology in forensic medicine has steadily expanded over the last two decades due to the favorable features of low cost, rapidity, high throughput, user-friendliness, contamination-free, and minimum sample and reagent consumption. In this context, bibliometric methods were adopted to visualize the literature information contained in the Science Citation Index Expanded from 1989 to 2022, focusing on the co-occurrence analysis of forensic and microfluidic topics. A deep interpretation of the literature was conducted based on co-occurrence results, in which microfluidic technologies and their applications in forensic medicine, particularly forensic genetics, were elaborated. The purpose of this review is to provide an impartial evaluation of the utilization of microfluidic technology in forensic medicine. Additionally, the challenges and future trends of implementing microfluidic technology in forensic genetics are also addressed.

An Integrated Portable Multiplex Microchip Device for Fingerprinting Chemical Warfare Agents

The rapid and reliable detection of chemical and biological agents in the field is important for many applications such as national security, environmental monitoring, infectious diseases screening, and so on. Current commercially available devices may suffer from low field deployability, specificity, and reproducibility, as well as a high false alarm rate. This paper reports the development of a portable lab-on-a-chip device that could address these issues. The device integrates a polymer multiplexed microchip system, a contactless conductivity detector, a data acquisition and signal processing system, and a graphic/user interface. The samples are pre-treated by an on-chip capillary electrophoresis system. The separated analytes are detected by conductivity-based microsensors. Extensive studies are carried out to achieve satisfactory reproducibility of the microchip system. Chemical warfare agents soman (GD), sarin (GB), O-ethyl S-[2-diisoproylaminoethyl] methylphsophonothioate (VX), and their degradation products have been tested on the device. It was demonstrated that the device can fingerprint the tested chemical warfare agents. In addition, the detection of ricin and metal ions in water samples was demonstrated. Such a device could be used for the rapid and sensitive on-site detection of both chemical and biological agents in the future.

Visual detection of a nerve agent simulant using chemically modified paper strips and dye-assembled inorganic nanocomposite

Chromogenic probe with oxidized bis-indolyl scaffold has been synthesized for the detection of a nerve gas mimicking agent, DCNP (diethyl cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the release of cyanide ion through the indole group mediating the hydrolysis of phosphorous-hetero atom bond and, thereafter, the Michael addition of the liberated CN^- ion to the electron deficient C[double bond, length as m-dash]C bond of the bis-indolyl moiety. The reaction featured a remarkable change in color from red to colorless at ambient condition. Then, low-cost and portable paper strips were designed for a rapid and on-site vapor phase detection of DCNP without involving any sophisticated instrument or skilled personnel. Finally, a dye assembled inorganic nanocomposite material was devised to achieve a more sensitive 'turn-on' detection of DCNP in water.

Triphenylamine–benzimidazole based switch offers reliable detection of organophosphorus nerve agent (DCP) both in solution and gaseous state

Triphenylamine-conjugated imidazole dye acts as a potential sensor for the liquid and vapour phase detection of nerve agent simulantDCP.

An innovative chemical strategy for PCR-free genetic detection of pathogens by an integrated electrochemical biosensor

An innovative chemical strategy integrated in a miniaturized electrochemical device was developed for sensitive detection of a pathogen genome (HBV virus) without any amplification step.

Nanomotors responsive to nerve-agent vapor plumes

Enzyme-powered nanomotors responsive to the presence of nerve agents in the surrounding atmosphere are employed for remote detection of chemical vapor threats. Distinct changes in the propulsion behavior, associated with the partition of the sarin simulant diethyl chlorophosphate (DCP), offer reliable and rapid detection of the nerve-agent vapor threat.

Modeling Barrier Tissues In Vitro: Methods, Achievements, and Challenges

Organ-on-a-chip devices have gained attention in the field of in vitro modeling due to their superior ability in recapitulating tissue environments compared to traditional multiwell methods. These constructed growth environments support tissue differentiation and mimic tissue-tissue, tissue-liquid, and tissue-air interfaces in a variety of conditions. By closely simulating the in vivo biochemical and biomechanical environment, it is possible to study human physiology in an organ-specific context and create more accurate models of healthy and diseased tissues, allowing for observations in disease progression and treatment. These chip devices have the ability to help direct, and perhaps in the distant future even replace animal-based drug efficacy and toxicity studies, which have questionable relevance to human physiology. Here, we review recent developments in the in vitro modeling of barrier tissue interfaces with a focus on the use of novel and complex microfluidic device platforms.

Amine Analysis Using AlexaFluor 488 Succinimidyl Ester and Capillary Electrophoresis with Laser-Induced Fluorescence

Fluorescent probes enable detection of otherwise nonfluorescent species via highly sensitive laser-induced fluorescence. Organic amines are predominantly nonfluorescent and are of analytical interest in agricultural and food science, biomedical applications, and biowarfare detection. Alexa Fluor 488 N-hydroxysuccinimidyl ester (AF488 NHS-ester) is an amine-specific fluorescent probe. Here, we demonstrate low limit of detection of long-chain (C9 to C18) primary amines and optimize AF488 derivatization of long-chain primary amines. The reaction was found to be equally efficient in all solvents studied (dimethylsulfoxide, ethanol, and N,N-dimethylformamide). While an organic base (N,N-diisopropylethylamine) is required to achieve efficient reaction between AF488 NHS-ester and organic amines with longer hydrophobic chains, high concentrations (>5 mM) result in increased levels of ethylamine and propylamine in the blank. Optimal incubation times were found to be >12 hrs at room temperature. We present an initial capillary electrophoresis separation for analysis using a simple micellar electrokinetic chromatography (MEKC) buffer consisting of 12 mM sodium dodecylsulfate (SDS) and 5 mM carbonate, pH 10. Limits of detection using the optimized labeling conditions and these separation conditions were 5-17 nM. The method presented here represents a novel addition to the arsenal of fluorescent probes available for highly sensitive analysis of small organic molecules.

Bioelectronic nose combined with a microfluidic system for the detection of gaseous trimethylamine

A bioelectronic nose based on a novel microfluidic system (μBN) was fabricated to detect gaseous trimethylamine (TMA) in real-time. Single-walled carbon nanotube-field effect transistors (SWNT-FETs) were functionalized with olfactory receptor-derived peptides (ORPs) that can recognize the TMA molecules. The ORP-coated SWNT-FETs were assembled with a microfluidic channel and were sealed with top and bottom frames. This simple process was used to complete the μBNs, and a well-defined condition was achieved to detect the gaseous molecules. The μBNs allowed us to detect gaseous TMA molecules down to 10 parts per trillion (ppt) in real-time and showed high selectivity when distinguishing gaseous TMA from other gaseous odorants. The sensor was used to determine the quality of seafood (oysters), and spoiled seafood and other types of spoiled foods were also successfully discriminated without any pretreatment processes. These results indicate that portable-scale platforms can be manufactured by using μBNs and can be applicable for real-time on-site gas analysis.

Rapid, sensitive, and quantitative detection of pathogenic DNA at the point of care through microfluidic electrochemical quantitative loop-mediated isothermal amplification

Single-step DNA detection: a microfluidic electrochemical loop mediated isothermal amplification platform is reported for rapid, sensitive, and quantitative detection of pathogen genomic DNA at the point of care. DNA amplification was electrochemically monitored in real time within a monolithic microfluidic device, thus enabling the detection of as few as 16 copies of Salmonella genomic DNA through a single-step process in less than an hour.

Effect of diffusion on impedance measurements in a hydrodynamic flow focusing sensor

This paper investigated the effects of diffusion between non-conductive sheath and conductive sample fluids in an impedance-based biosensor. Impedance measurements were made with 2- and 4-electrode configurations. The 4-electrode design offers the advantage of impedance measurements at low frequencies (<1 kHz) without the deleterious effects of double layer impedance which are present in the 2-electrode design. Hydrodynamic flow focusing was achieved with a modified T-junction design with a smaller cross-section for the sample channel than for the focusing channel, which resulted in 2D focusing of the sample stream with just one sheath stream. By choosing a non-conductive sheath fluid and a conductive sample fluid, the electric field was confined to the focused stream. In order to utilize this system for biosensing applications, we characterized it for electrical and flow parameters. In particular, we investigated the effects of varying flow velocities and flow-rate ratios on the focused stream. Increasing flow-rate ratios reduced the cross-sectional area of the focused streams as was verified by finite element modeling and confocal microscopy. Antibody mediated binding of Escherichia coli to the electrode surface caused an increase in solution resistance at low frequencies. The results also showed that the diffusion mass transport at the interface of the two streams limited the benefits of increased flow focusing. Increasing flow velocities could be used to offset the diffusion effect. To optimize detection sensitivity, flow parameters and mass transport must be considered in conjunction, with the goal of reducing diffusion of conducting species out of the focused stream while simultaneously minimizing its cross-sectional area.

Evaporative self-assembly assisted synthesis of polymeric nanoparticles by surface acoustic wave atomization

We demonstrate a straightforward and rapid atomization process driven by surface acoustic waves that is capable of continuously producing spherical monodispersed submicron poly-ε-caprolactone particle aggregates between 150 and 200 nm, each of which are composed of nanoparticles of 5-10 nm in diameter. The size and morphologies of these particle assemblies were determined using dynamic light scattering, atomic force microscopy and transmission electron microscopy. Through scaling theory, we show that the larger particle aggregates are formed due to capillary instabilities amplified by the acoustic forcing whereas the smaller particulates that form the aggregates arise due to a nucleate templating process as a result of rapid spatially inhomogeneous solvent evaporation. Minimization of the free energy associated with the evaporative process yields a critical cluster size for a single nucleus in the order of 10 nm, which roughly corresponds with the dimensions of the sub-50 nm particulates.

Photochemical functionalization of polymer surfaces for microfabricated devices

Herein we report the topochemical modification of polymer surfaces with perfluorinated aromatic azides. The aryl azides, which have quaternary amine or aldehyde functional groups, were linked to the surface of the polymer by UV irradiation. The polymer substrates used in this study were cyclic olefin copolymer and poly(methyl methacrylate). These substrates were characterized before and after modification using reflection-absorption infrared spectroscopy, sessile water contact angle measurements, and X-ray photoelectron spectroscopy. Analysis of the surface confirmed the presence of aromatic groups with aldehyde or quaternary amine functionality. Enzyme immobilization and patterning onto polymer surfaces were studied using confocal microscopy. Enzymatic digests of protein were carried out on modified probes manufactured from thermoplastic substrates, and the resulting peptide analysis was completed using matrix-assisted laser desorption/ionization mass spectrometry. The use of functionalized perfluorinated aromatic azides allows the surface chemistry of thermoplastics to be tailored for specific lab-on-a-chip applications.

Forensic DNA Analysis on Microfluidic Devices: A Review

The advent of microfluidic technology for genetic analysis has begun to impact forensic science. Recent advances in microfluidic separation of short-tandem-repeat (STR) fragments has provided unprecedented potential for improving speed and efficiency of DNA typing. In addition, the analytical processes associated with sample preparation--which include cell sorting, DNA extraction, DNA quantitation, and DNA amplification--can all be integrated with the STR separation in a seamless manner. The current state of these microfluidic methods as well as their advantages and potential shortcomings are detailed. Recent advances in microfluidic device technology, as they pertain to forensic DNA typing, are discussed with a focus on the forensic community.

Microfluidic chip for fast bioassays-evaluation of binding parameters

A seven channel polystyrene (PS) microchip has been constructed using a micromilling machine and a high-temperature assembling. Protein A (PA) has been immobilized by a passive sorption on the microchannel walls. Two bioaffinity assays with human immunoglobulin G (hIgG) as a ligand have been carried out. (i) PA as the receptor and fluorescently labeled hIgG (FITC-hIgG) as the ligand, (ii) PA as the receptor with hIgG as the quantified ligand and fluorescently labeled goat anti-human IgG (FITC-gIgG) as the secondary ligand. One incubation step of the assays took only 5 min instead of hours typical for enzyme-linked immunosorbent assay applications. Calibration curves of the dependence of a fluorescence signal on the hIgG concentration in a sample have been obtained in one step due to a parallel arrangement of microchannels. A mathematical model of the PA-FITC-hIgG complex formation in the chip has been developed. The values of the kinetic constant of the PA-FITC-hIgG binding (k(on)=5.5 m(3) mol(-1) s(-1)) and the equilibrium dissociation constant of the formed complex (K(d)</=3x10(-6) mol m(-3)) have been obtained by fitting to experimental data. The proposed microchip enables fast evaluation of kinetic and equilibrium constants of ligand-receptor bioaffinity pairs and the ligand quantification. As the use of microfluidic chips for immunoassays is often limited by price, we used procedures and chemicals that allow for an inexpensive construction and operation of the microdevice, e.g., temperature assembling as a fabrication technique, detection via an ordinary digital camera, nonspecific polystyrene as a substrate, passive sorption of biomolecules as an immobilization technique, etc.

Analytical and On-site Detection Methods for Chemical Warfare Agents

Chemical warfare agents (CWAs) are fast acting and sometimes lethal, even at low levels, and can be classified into nerve gases, blister agents, choking agents, blood agents, vomit agents, tear gases, and incapacitating agents. As countermeasures against CWA terrorism, detection and identification are important. In crisis management, monitoring of CWAs in public places and security checks at territorial borders, big event venues, and executive facilities are performed for protection against terrorism. In consequence management, on-site detection by first responders and laboratory analysis after on-site sampling and transfer are performed for minimization of terrorism damage, leading to personal protection, initial investigation, and emergency lifesaving. In incident management, laboratory analysis is performed to provide evidence at court trials for the prevention of future crimes. Laboratory analysis consists of pretreatment of on-site and casualty samples and instrumental analysis using GC-MS. However, CWAs are easily degraded, and thus are difficult to detect. Instead, it is useful to detect their metabolites and degradation products using tert-butyldimethylsilyl derivatization GC-MS or direct LC-MS. Commercially available chemical detection equipment such as gas detection tubes and ion mobility spectrometers are used for on-site detection. We have evaluated the detection performance of such equipment and found that no equipment fulfills the required perfect performance of CWA detection sensitivity, accuracy, response time, return time, and operation. To overcome the drawbacks, we have adopted the monitoring tape method and counterflow introduction atmospheric pressure chemical ionization mass spectrometry and recommend the combination of commercial detection equipment and these new technologies for simultaneous, rapid detection of all CWAs.

Use of Biosensors for Detecting Organophosphorus Agents

The present paper reviews the use of electrochemical biosensors for detecting organophosphorus pesticides and nerve agents. Acetylcholine esterase (AChE)-immobilized electrodes have been used for detecting AChE inhibitors including organophosphorus and carbamate pesticides. The sensors are composed of AChE and choline oxidase (ChOx) for converting the AChE-generated choline into betaine and hydrogen peroxide (H(2)O(2)), which is electrochemically oxidized at the electrode surface to produce the output signal of the sensor. In the presence of AChE inhibitors, the suppressed output signal of the sensor can be observed. If the sensors are operated in the presence of acetylthiocholine as a substrate of AChE, one can eliminate ChOx from the sensor design because enzymatically generated thiocholine is electrochemically active and thus directly oxidized at the electrode without using ChOx. Electron-transfer mediators such as tetracyanoquinodimethane have often been used for catalytically oxidizing thiocholine at the electrode set at less positive potential, which is effective in circumventing possible interference arising from oxidizing compounds in the sample solution. One of the drawbacks of the AChE-based biosensors in detecting organophosphorus pesticides and nerve agents arises from the fact that the sensors indirectly detect the signal based on the inhibition of the AChE-catalyzed reaction. On the other hand, for directly obtaining the output signal, organophosphorus hydrolase (OPH) is immobilized on the electrode surface to prepare amperometric biosensors. OPH catalyzes the hydrolysis reaction of organophosphorus compounds to produce electrochemically active compounds such as p-nitrophenol and thiols from parathion and VX, respectively. Thus OPH-based sensors can be used for detecting these compounds directly. These biosensors would be useful for in-site measurements of organophosphorus pesticides and nerve agents because portable-type biosensors are easily fabricated at relatively low cost.

Utilisation of separation methods in the analysis of chemical warfare agents

Chemical warfare agents and their degradation products represent a broad group of compounds with different chemical properties (polarity, volatility, thermostability, etc.). These chemicals often have to be detected and determined in complex matrices and therefore highly efficient separation techniques hyphenated to selective and sensitive detectors play an indispensable role. This review offers an overview of selected papers devoted to the title subject. It cannot be considered as a comprehensive literature compilation but should allow the reader to obtain an insight into the application of separation techniques in the important area of human protection and control of chemical weapons.