Fluorescent Chemosensors for Toxic Organophosphorus Pesticides: A Review
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paper_title: Ecological perspective on water quality goals

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The central assumption of nonpoint source pollution control efforts in agricultural watersheds is that traditional erosion control programs are sufficient to insure high quality water resources. We outline the inadequacies of that assumption, especially as they relate to the goal of attaining ecological integrity. The declining biotic integrity of our water resources over the past two decades is not exclusively due to water quality (physical/chemical) degradation. Improvement in many aspects of the quality of our water resources must be approached with a much broader perspective than improvement of physical/chemical conditions. Other deficiencies in nonpoint pollution control programs are discussed and a new approach to the problem is outlined.
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paper_title: Natural and synthetic organic compounds in the environment-a symposium report.

paper_content:

Abstract In March 2000, an international two-day symposium was organized in Noordwijkerhout, The Netherlands, on ‘Natural and synthetic organic compounds in the environment’. The emphasis of the symposium was on the following classes of compounds: polycyclic aromatic hydrocarbons, xeno-estrogens, phyto-estrogens, and veterinary drugs. Sources, environmental distribution, uptake, biotransformation and toxic effects from the molecular to the population level were discussed. Other important aspects were the development of biomarkers, analytical methods, bioassays, molecular modelling and other research tools. Finally, the implications of the findings for government policies were discussed. In this paper, a summary is given of the most important facts and views presented at the symposium.
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paper_title: TESTING WATER QUALITY FOR PESTICIDE POLLUTION

paper_content:

Information from the first phase of the USA's National Water Quality Assessment (NAWQA) Program shows that pesticides are widespread in streams and ground water, and occur in geographical and seasonal patterns that follow land use and related pesticide use. The most heavily used compounds account for most detections, and most pesticides found in the environment usually occur as mixtures. Almost every stream sample collected contained at least one pesticide. For drinking water, the NAWQA results usually provide good news about individual pesticides in relation to current regulations and criteria. However, the extent of risk to humans here is not yet known, because the criteria cover limited numbers of pesticides and potential effects. The NAWQA results show a high potential for pesticide impacts on aquatic life in some streams, especially those where concentrations of more than one pesticide approach or exceed aquatic-life criteria for long time periods. This feature describes the NAWQA Programs's scope and structure, discusses the widespread occurrence of pesticides in natural waters, gives examples of use-detection relationships and considers the environmental significance of the Programs's findings and their implications for NAWQA. The NAWQA design may be modified to improve assessment in future studies.
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paper_title: Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides

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OBJECTIVE ::: The goal was to examine the association between urinary concentrations of dialkyl phosphate metabolites of organophosphates and attention-deficit/hyperactivity disorder (ADHD) in children 8 to 15 years of age. ::: ::: ::: METHODS ::: Cross-sectional data from the National Health and Nutrition Examination Survey (2000-2004) were available for 1139 children, who were representative of the general US population. A structured interview with a parent was used to ascertain ADHD diagnostic status, on the basis of slightly modified criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. ::: ::: ::: RESULTS ::: One hundred nineteen children met the diagnostic criteria for ADHD. Children with higher urinary dialkyl phosphate concentrations, especially dimethyl alkylphosphate (DMAP) concentrations, were more likely to be diagnosed as having ADHD. A 10-fold increase in DMAP concentration was associated with an odds ratio of 1.55 (95% confidence interval: 1.14-2.10), with adjustment for gender, age, race/ethnicity, poverty/income ratio, fasting duration, and urinary creatinine concentration. For the most-commonly detected DMAP metabolite, dimethyl thiophosphate, children with levels higher than the median of detectable concentrations had twice the odds of ADHD (adjusted odds ratio: 1.93 [95% confidence interval: 1.23-3.02]), compared with children with undetectable levels. ::: ::: ::: CONCLUSIONS ::: These findings support the hypothesis that organophosphate exposure, at levels common among US children, may contribute to ADHD prevalence. Prospective studies are needed to establish whether this association is causal.
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paper_title: Integrated Human and Ecological Risk Assessment: A Case Study of Organophosphorous Pesticides in the Environment

paper_content:

This study was chosen as an example of integrated risk assessment because organophosphorous esters (OPs) share exposure characteristics for different species, including human beings and because a common mechanism of action can be identified. The “Framework for the integration of health and ecological risk assessment” is being tested against a deterministic integrated environmental health risk assessment for OPs used in a typical farming community. It is argued that the integrated approach helps both the risk manager and the risk assessor in formulating a more holistic approach toward the risk of the use of OP-esters. It avoids conclusions based on incomplete assessments or on separate assessments. The database available can be expanded and results can be expressed in a more coherent manner. In the integrated exposure assessment of OPs, the risk assessments for human beings and the environment share many communalities with regards to sources and emissions, distribution routes and exposure scenarios. The site of action of OPs, acetylcholinesterase, has been established in a vast array of species, including humans. It follows that in the integrated approach the effects assessment for various species will show communalities in reported effects and standard setting approaches. In the risk characterization, a common set of evidence, common criteria, and common interpretations of those criteria are used to determine the cause of human and ecological effects that co-occur or are apparently associated with exposure to OPs. Results of health and ecological risk assessments are presented in a common format that facilitates comparison of results. It avoids acceptable risk conclusions with regard to the environment, which are unacceptable with regard to human risk and vice versa. Risk managers will be prompted to a more balanced judgement and understanding and acceptance of risk reduction measures will be facilitated.
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paper_title: Fluorescent sensors for organophosphorus nerve agent mimics.

paper_content:

We present a small molecule sensor that provides an optical response to the presence of an organophosphorus (OP)-containing nerve agent mimic. The design contains three key features: a primary alcohol, a tertiary amine in close proximity to the alcohol, and a fluorescent group used as the optical readout. In the sensor's rest state, the lone pair of electrons of the basic amine quenches the fluorescence of the nearby fluorophore through photoinduced electron transfer (PET). Exposure to an OP nerve agent mimic triggers phosphorylation of the primary alcohol followed rapidly by an intramolecular substitution reaction as the amine displaces the created phosphate. The quaternized ammonium salt produced by this cyclization reaction no longer possesses a lone pair of electrons, and a fluorescence readout is observed as the nonradiative PET quenching pathway of the fluorophore is shut down.
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paper_title: Electrochemical sensor for organophosphate pesticides and nerve agents using zirconia nanoparticles as selective sorbents.

paper_content:

An electrochemical sensor for detection of organophosphate (OP) pesticides and nerve agents using zirconia (ZrO2) nanoparticles as selective sorbents is presented. Zirconia nanoparticles were electrodynamically deposited onto the polycrystalline gold electrode by cyclic voltammetry. Because of the strong affinity of zirconia for the phosphoric group, nitroaromatic OPs strongly bind to the ZrO2 nanoparticle surface. The electrochemical characterization and anodic stripping voltammetric performance of bound OPs were evaluated using cyclic voltammetric and square-wave voltammetric (SWV) analysis. SWV was used to monitor the amount of bound OPs and provide simple, fast, and facile quantitative methods for nitroaromatic OP compounds. The sensor surface can be regenerated by successively running SWV scanning. Operational parameters, including the amount of nanoparticles, adsorption time, and pH of the reaction medium have been optimized. The stripping voltammetric response is highly linear over the 5-100 ng/mL (ppb) methyl parathion range examined (2-min adsorption), with a detection limit of 3 ng/mL and good precision (RSD = 5.3%, n = 10). The detection limit was improved to 1 ng/mL by using 10-min adsorption time. The promising stripping voltammetric performances open new opportunities for fast, simple, and sensitive analysis of OPs in environmental and biological samples. These findings can lead to a widespread use of electrochemical sensors to detect OP contaminates.
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paper_title: Degradation of some pesticides in the field and effect of processing

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Standard methods have been applied for the analysis of pesticides, namely diazinon, azinphos-methyl, pirimicarb, methidathion, ethion and phosalone, used most frequently in the Elazig region. In order to find out the rates of degradation of pesticides on vegetables and fruit, the residues were analysed under native field conditions over a period of time. The effects of washing and peeling on the pesticide residue levels in fruits and vegetables were investigated. In addition, the effects of sunlight, volatilization and micro-organisms on the disappearance and fate of pesticide residues in the products were also studied in relation to time.
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paper_title: Biomaterials for Mediation of Chemical and Biological Warfare Agents

paper_content:

Recent events have emphasized the threat from chemical and biological warfare agents. Within the efforts to counter this threat, the biocatalytic destruction and sensing of chemical and biological weapons has become an important area of focus. The specificity and high catalytic rates of biological catalysts make them appropriate for decommissioning nerve agent stockpiles, counteracting nerve agent attacks, and remediation of organophosphate spills. A number of materials have been prepared containing enzymes for the destruction of and protection against organophosphate nerve agents and biological warfare agents. This review discusses the major chemical and biological warfare agents, decontamination methods, and biomaterials that have potential for the preparation of decontamination wipes, gas filters, column packings, protective wear, and self-decontaminating paints and coatings.
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paper_title: Colorimetric detection of chemical warfare simulants

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Two simple chromogenic indicators (4) and (5), containing different supernucleophilic moieties, have been synthesized. Upon phosphorylation with two chemical warfare agent (CWA) simulants, a hypsochromic shift of approximately 50 nm is observed in an NaOH–DMSO solution. The oximate supernucleophile was found to be a better supernucleophile than the hydrazone moiety. Two X-ray crystal structures were obtained from unexpected synthetic side products obtained in this study. These will also be discussed.
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paper_title: A supramolecular microfluidic optical chemosensor.

paper_content:

A supramolecular microfluidic optical chemosensor (muFOC) has been fabricated. A serpentine channel has been patterned with a sol-gel film that incorporates a cyclodextrin supramolecule modified with a Tb(3+) macrocycle. Bright emission from the Tb(3+) ion is observed upon exposure of the (mu)FOC to biphenyl in aqueous solution. The signal transduction mechanism was elucidated by undertaking steady-state and time-resolved spectroscopic measurements directly on the optical chemosensor patterned within the microfluidic network. The presence of biphenyl in the cyclodextrin receptor site triggers Tb(3+) emission by an absorption-energy transfer-emission process. These results demonstrate that the intricate signal transduction mechanisms of supramolecular optical chemosensors are successfully preserved in microfluidic environments.
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paper_title: Influence of surface-active compounds on the response and sensitivity of cholinesterase biosensors for inhibitor determination

paper_content:

The influence of non-ionogenic surfactants, i.e., Tween-20, Triton X-100 and PEG-10 000, on the response of cholinesterase-based potentiometric biosensors and their sensitivity towards reversible and irreversible inhibitors were investigated. Acetyl-and butyrylcholinesterases were immobilized on nylon, cellulose nitrate films and tracing paper and were introduced into an assembly of potentiometric biosensors. The effect of surface-active compounds depends on the hydrophilic properties and porosity of the enzyme support material and the inhibition mechanism. In the range 0.002–0.3% m/v the surfactants show a reversible inhibiting effect on biosensor response. At lower concentrations (down to 10–4% m/v) the surfactants alter the analytical characteristics of reversible and irreversible inhibitor determination. The use of surface-active additives improves the biosensor selectivity in multi-component media.
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paper_title: Fluorescent Detection of Chemical Warfare Agents: Functional Group Specific Ratiometric Chemosensors

paper_content:

Indicators providing highly sensitive and functional group specific fluorescent response to diisopropyl fluorophosphate (DFP, a nerve gas (G-agent) simulant) are reported. Nonemissive indicator 2 reacts with DFP to give a cyclized compound 2+A- that shows a high emission due to its highly planar and rigid structure. Very weak emission was observed by the addition of HCl. Another indicator based on pyridyl naphthalene exhibits a large shift in its emission spectrum after reaction with DFP, which provides for quantitative ratiometric detection.
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paper_title: Molecularly imprinted polymer sensors for pesticide and insecticide detection in water.

paper_content:

Antibodies, peptides, and enzymes are often used as molecular recognition elements in chemical and biological sensors. However, their lack of stability and signal transduction mechanisms limits their use as sensing devices. Recent advances in the field of molecularly imprinted polymers (MIPs) have created synthetic materials that can mimic the function of biological receptors but with less stability constraints. These polymers can provide high sensitivity and selectivity while maintaining excellent thermal and mechanical stability. To further enhance the advantages of the traditional imprinted polymer approach, an additional fluorescent component has been introduced into these polymers. Such a component provides enhanced chemical affinity as well as a method for signal transduction. In this type of imprinted polymer, binding of the target analyte invokes a specific spectral signature from the reporter molecule. Previous work has provided molecularly imprinted polymers that are selective for the hydrolysis products of organophosphorus species such as the nerve agents sarin and soman. (A. L. Jenkins, O. M. Uy and G. M. Murray, Anal. Chem., 1999, 71, 373). In this paper the direct imprinting of non-hydrolyzed organophosphates including pesticides and insecticides is described. Detection limits for these newly developed MIP sensors are less than 10 parts per trillion (ppt) with long linear dynamic ranges (ppt to ppm) and response times of less than 15 min.
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paper_title: Polymer-based lanthanide luminescent sensor for detection of the hydrolysis product of the nerve agent Soman in water.

paper_content:

The techniques of molecular imprinting and sensitized lanthanide luminescence have been combined to create the basis for a sensor that can selectively measure the hydrolysis product of the nerve agent Soman in water. The sensor functions by selectively and reversibly binding the phosphonate hydrolysis product of this agent to a functionality-imprinted copolymer possessing a coordinatively bound luminescent lanthanide ion, Eu3+. Instrumental support for this device is designed to monitor the appearance of a narrow luminescence band in the 610-nm region of the Eu3+ spectrum that results when the analyte is coordinated to the copolymer. The ligand field shifted luminescence was excited using 1 mW of the 465.8-nm line of an argon ion laser and monitored via an optical fiber using a miniature spectrometer. For this configuration, the limit of detection for the hydrolysis product is 7 parts per trillion (ppt) in solution with a linear range from 10 ppt to 10 ppm. Chemical and spectroscopic selectivities have been combined to reduce the likelihood of false positive analyses. Chemically analogous organophosphorus pesticides tested against the sensor have been shown to not interfere with determination.
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paper_title: Polymer based lanthanide luminescent sensors for the detection of nerve agents

paper_content:

Several devices are being constructed to measure and detect the nerve ::: agents Sarin and Soman. The devices function by selectively binding the ::: phosphonate hydrolysis products to a luminescent functionality-imprinted ::: copolymer. The copolymers possess a securely bound luminescent lanthanide ::: ion, such as Eu ::: 3 ::: ::: + ::: , in a coordination complex that ::: has been templated for the chemical functionality resulting from the ::: hydrolysis of Sarin and Soman but has had a weakly bound anion substituted ::: by mass action. The instrumental support for the device is being designed ::: to monitor the change that occurs in the luminescence spectrum of the ::: lanthanide when the analyte is coordinated. The ligand field shifted ::: luminescence of the lanthanide is excited by a compact laser and monitored ::: via optical fiber by either a filter photometer or a ::: monochromator. Miniaturization will be applied to each of the lab bench ::: components to produce a field portable device that will potentially be ::: comparable in size to a pH meter. Initial results using an Ar ion laser ::: excitation source providing 0.3 mW at 465.7 nm yield a limit of detection ::: of 125 ppt. The chemical and spectroscopic selectivity of this device are ::: being combined to reduce the likelihood of false positive analyses.
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paper_title: Studies on a surface acoustic wave (SAW) dosimeter sensor for organophosphorous nerve agents

paper_content:

As a follow-up of previous work on a Surface Acoustic Wave (SAW) sensor for nerve agents, irreversible response effects have been studied in more detail. Surface analytical studies indicated that degradation products are responsible for the effects observed. In addition it was tried to explore these effects for the development of a nerve agent dosimeter. Experiments were conducted to test the performance of a SAW sensor coated with La(III) 2-bis(carboxymethyl)amino hexadecanoic acid. The experiments revealed that many improvements must be made especially with respect to sensitivity and linear response behaviour. © 1997 Elsevier Science S.A.
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paper_title: Detection of a Chemical Warfare Agent Simulant in Various Aerosol Matrixes by Ion Mobility Time-of-Flight Mass Spectrometry

paper_content:

For the first time, a traditional radioactive nickel (63Ni) beta emission ionization source for ion mobility spectrometry was employed with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer (IM(tof)MS) to detect a chemical warfare agent (CWA) simulant from aerosol samples. Aerosol-phase sampling employed a quartz cyclonic chamber for sample introduction. The simulant reference material, which closely mimicked the characteristic chemical structure of CWAs as defined and described by Schedule 1, 2, or 3 of the Chemical Warfare Convention treaty verification, was used in this study. An overall elevation in arbitrary signal intensity of approximately 1.0 orders of magnitude was obtained by the progressive increase of the thermal AP-IMS temperature from 75 to 275 degrees C. A mixture of one G-type nerve simulant (dimethyl methylphosphonate (DMMP)) in four (water, kerosene, gasoline, diesel) matrixes was found in each case (AP-IMS temperature 75-275 degrees C) to be clearly resolved in less than 2.20 x 10(4) micros using the IM(tof)MS instrument. Corresponding ions, masses, drift times, K(o) values, and arbitrary signal intensities for each of the sample matrixes are reported for the CWA simulant DMMP.
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paper_title: Determination of Pesticides Using Electrochemical Enzymatic Biosensors

paper_content:

In the recent decade numerous biosensing methods for detection of pesticides have been developed using integrated enzymatic biosensors and immunosensors. Enzymatic determination of pesticides is most often based on inhibition of the activity of selected enzymes such as cholinesterases, organophosphate hydrolase, alkaline and acid phosphatase, ascorbate oxidase, acetolactate synthase and aldehyde dehydrogenase. Enzymatic biosensors were developed using various electrochemical signal transducers, different methods of enzyme immobilization and various measuring methodologies. Application of single-use screen-printed biosensors in batch measurements and flow-injection analysis with enzyme biosensors are most intensively developed procedures. An improvement of detectability level can be achieved by the use of recombinant enzyme mutants, while multi-component determinations by the use of biosensor matrices and data processing with artificial neural networks. In some cases the determined pesticide can be also a substrate of enzymatic reaction. Another area of development of biosensors for determination of pesticides is in the design of microbial biosensors and photosystem-based biosensors with electrochemical biosensors.
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paper_title: Cooperation between Artificial Receptors and Supramolecular Hydrogels for Sensing and Discriminating Phosphate Derivatives

paper_content:

This study has successfully demonstrated that the cooperative action of artificial receptors with semi-wet supramolecular hydrogels may produce a unique and efficient molecular recognition device not only for the simple sensing of phosphate derivatives, but also for discriminating among phosphate derivatives. We directly observed by confocal laser scanning microscopy that fluorescent artificial receptors can dynamically change the location between the aqueous cavity and the hydrophobic fibers upon guest-binding under semi-wet conditions provided by the supramolecular hydrogel. On the basis of such a guest-dependent dynamic redistribution of the receptor molecules, a sophisticated means for molecular recognition of phosphate derivatives can be rationally designed in the hydrogel matrix. That is, the elaborate utilization of the hydrophobic fibrous domains, as well as the water-rich hydrophilic cavities, enables us to establish three distinct signal transduction modes for phosphate sensing: the use of (i) ...
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paper_title: Highly Sensitive and Selective Amperometric Microbial Biosensor for Direct Determination ofp-Nitrophenyl-Substituted Organophosphate Nerve Agents

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We report herein a whole cell-based amperometric biosensor for highly selective, highly sensitive, direct, single-step, rapid, and cost-effective determination of organophosphate pesticides with a p-nitrophenyl substituent. The biosensor was comprised of a p-nitrophenol degrader, Pseudomonas putida JS444, genetically engineered to express organophosphorus hydrolase (OPH) on the cell surface immobilized on the carbon paste electrode. Surface-expressed OPH catalyzed hydrolysis of the p-nitrophenyl substituent organophosphorus pesticides such as paraoxon, parathion, and methyl parathion to release p-nitrophenol, which was subsequently degraded by the enzymatic machinery of P. putida JS444. The electrooxidization current of the intermediates was measured and correlated to the concentration of organophosphates. The best sensitivity and response time were obtained using a sensor constructed with 0.086 mg dry weight of cells operating at 600 mV applied potential (vs Ag/AgCl reference) in 50 mM citrate--phosphate pH 7.5 buffer with 50 microM CoCl2 at room temperature. Under optimum operating conditions the biosensor measured as low as 0.28 ppb of paraoxon, 0.26 ppb of methyl parathion, and 0.29 ppb parathion. These detection limits are comparable to cholinesterase inhibition-based biosensors. Unlike the inhibition-based format, this biosensor manifests a selective response to organophosphate pesticides with a p-nitrophenyl substituent only, has a simplified single-step protocol with short response time, and can be used for repetitive/multiple and on-line analysis. The service life of the microbial amperometric biosensor was 5 days when stored in the operating buffer at 4 degrees C. The new biosensor offers great promise for rapid environmental monitoring of OP pesticides with nitrophenyl substituent.
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paper_title: Spectrophotometric detection of organophosphate diazinon by porphyrin solution and porphyrin-dyed cotton fabric

paper_content:

Abstract The absorbance spectrum of porphyrin meso-tetraphenylporphine (TPP) shifts to a shorter wavelength when interacting with the organophosphate diazinon. This spectral shift in the presence of diazinon is more obvious in the difference spectra (TPP + diazinon) − TPP, and can be observed in porphyrin–DMF solution and porphyrin-dyed cotton fabric. In solution, the difference spectrum has a peak at 412 nm and a trough at 421 nm. For TPP dyed cotton fabric, the difference spectrum has a peak at 415 nm and a trough at 430 nm. The absorbance difference (Δ A ) between peak and trough in the difference spectra has a linear relationship with diazinon concentration. This spectral property of porphyrin can be used to detect diazinon in the environment. Diazinon can be detected at 0.5 ppm level by TPP in solution, and at 11 ppm level by TPP dyed cotton fabric. The solid state detection capability of TPP dyed cotton fabric implies that textiles can serve as the platform for chemical sensors.
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paper_title: Acetylcholinesterase in organic solvents for the detection of pesticides: Biosensor application

paper_content:

Abstract Acetylcholinesterase (AChE) from electric eel, in a free or immobilized state, can be used for the detection of insecticides. This system is convenient because of the selectivity and specificity of the inhibition of AChE by organophosphorus and carbamate insecticides. However, these pesticides are highly soluble only in organic solvents. This article deals with the determination of the activity of AChE in organic solvents. Firstly, the effect of different organic solvents on activity was determined using the free enzyme. The AChE activity was maintained using the free enzyme. The AChE activity was maintained depending on the nature of the solvent. The results were applied to the biosensing system and a new method for the detection of organophosphorus and carbamate insecticides was developed. A correlation between the AChE activity and a physico-chemical parameter, was found in order to predict the effect of the solvent on enzyme activity. Upon comparison of the correlation curve obtained with free and immobilized enzyme, it appeared that immobilization enhanced the stability of the enzyme and increased the number of usable organic solvents. The inhibition of AChE by organophosphorus and carbamate insecticides was tested in organic solvents and the limit of detection determined. The inhibitory capacity of AChE was maintained in most organic solvents. The reactivation of immobilized enzyme with 2-pyridine aldoxime methiodide (2-PAM) allowed the repeated use of the same enzyme electrode. The application of the biosensor for the detection of organophosphorus and carbamate insecticides in organic solvents using chemical knowledge will be useful for the detection of pesticide residues present in water and food at very low levels.
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paper_title: Biomaterials for Mediation of Chemical and Biological Warfare Agents

paper_content:

Recent events have emphasized the threat from chemical and biological warfare agents. Within the efforts to counter this threat, the biocatalytic destruction and sensing of chemical and biological weapons has become an important area of focus. The specificity and high catalytic rates of biological catalysts make them appropriate for decommissioning nerve agent stockpiles, counteracting nerve agent attacks, and remediation of organophosphate spills. A number of materials have been prepared containing enzymes for the destruction of and protection against organophosphate nerve agents and biological warfare agents. This review discusses the major chemical and biological warfare agents, decontamination methods, and biomaterials that have potential for the preparation of decontamination wipes, gas filters, column packings, protective wear, and self-decontaminating paints and coatings.
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paper_title: A supramolecular microfluidic optical chemosensor.

paper_content:

A supramolecular microfluidic optical chemosensor (muFOC) has been fabricated. A serpentine channel has been patterned with a sol-gel film that incorporates a cyclodextrin supramolecule modified with a Tb(3+) macrocycle. Bright emission from the Tb(3+) ion is observed upon exposure of the (mu)FOC to biphenyl in aqueous solution. The signal transduction mechanism was elucidated by undertaking steady-state and time-resolved spectroscopic measurements directly on the optical chemosensor patterned within the microfluidic network. The presence of biphenyl in the cyclodextrin receptor site triggers Tb(3+) emission by an absorption-energy transfer-emission process. These results demonstrate that the intricate signal transduction mechanisms of supramolecular optical chemosensors are successfully preserved in microfluidic environments.
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paper_title: Fluorescent Sensors for the Detection of Chemical Warfare Agents

paper_content:

Along with biological and nuclear threats, chemical warfare agents are some of the most feared weapons of mass destruction. Compared to nuclear weapons they are relatively easy to access and deploy, which makes them in some aspects a greater threat to national and global security. A particularly hazardous class of chemical warfare agents are the nerve agents. Their rapid and severe effects on human health originate in their ability to block the function of acetylcholinesterase, an enzyme that is vital to the central nervous system. This article outlines recent activities regarding the development of molecular sensors that can visualize the presence of nerve agents (and related pesticides) through changes of their fluorescence properties. Three different sensing principles are discussed: enzyme-based sensors, chemically reactive sensors, and supramolecular sensors. Typical examples are presented for each class and different fluorescent sensors for the detection of chemical warfare agents are summarized and compared.
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paper_title: Characterization of organophosphorus hydrolases and the genetic manipulation of the phosphotriesterase from Pseudomonas diminuta

paper_content:

Abstract There are a variety of enzymes which are specifically capable of hydrolyzing organophosphorus esters with different phosphoryl bonds from the typical phosphotriester bonds of common insecticidal neurotoxins (e.g. paraoxon or coumaphos) to the phosphonate-fluoride bonds of chemical warfare agents (e.g. soman or sarin). These enzymes comprise a diverse set of enzymes whose basic architecture and substrate specificities vary dramatically, yet they appear to be ubiquitous throughout nature. The most thoroughly studied of these enzymes is the organophosphate hydrolase (opd gene product) of Pseudomonas diminuta and Flavobacterium sp. ATCC 27551, and the heterologous expression, post-translational modification, and genetic engineering studies undertaken with this enzyme are described.
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paper_title: Acetylcholinesterase Fiber-Optic Biosensor for Detection of Anticholinesterases

paper_content:

An optical sensor for anticholinesterases (AntiChEs) was constructed by immobilizing fluorescein isothiocyanate (FITC)-tagged eel electric organ acetylcholinesterase (AChE) on quartz fibers and monitoring enzyme activity. The pH-dependent fluorescent signal generated by FITC-AChE, present in the evanescent zone on the fiber surface, was quenched by the protons produced during acetylcholine (ACh) hydrolysis. Analysis of the fluorescence response showed Michaelis-Menten kinetics with a Kapp value of 420 microM for ACh hydrolysis. The reversible inhibitor edrophonium (0.1 mM) inhibited AChE and consequently reduced fluorescence quenching. The biosensor response immediately recovered upon its removal. The carbamate neostigmine (0.1 mM) also inhibited the biosensor response but recovery was much slower. In the presence of ACh, the organophosphate (OP) diisopropylfluorophosphate (DFP) at 0.1 mM did not interfere with the ACh-dependent fluorescent signal quenching, but preexposure of the biosensor to DFP in absence of ACh inhibited totally and irreversibly the biosensor response. However, the DFP-treated AChE biosensor recovered fully after a 10-min perfusion with pralidoxime (2-PAM). Echothiophate, a quaternary ammonium OP, inhibited the ACh-induced fluorescence quenching in the presence of ACh and the phosphorylated biosensor was reactivated with 2-PAM. These effects reflected the mechanism of action of the inhibitors with AChE and the inhibition constants obtained were comparable to those from colorimetric methods. The biosensor detected concentrations of the carbamate insecticides bendiocarb and methomyl and the OPs echothiophate and paraoxon in the nanomolar to micromolar range. Malathion, parathion, and dicrotophos were not detected even at millimolar concentrations; however, longer exposure or prior modification of these compounds (i.e., to malaoxon, paraoxon) may increase the biosensor detection limits. This AChE biosensor is fast, sensitive, reusable, and relatively easy to operate. Since the instrument is portable and can be self-contained, it shows potential adaptability to field use.
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paper_title: Detection of paraoxon by immobilized organophosphorus hydrolase in a Langmuir–Blodgett film

paper_content:

Abstract Langmuir–Blodgett (LB) film deposition technique was employed for the immobilization of organophosphorus hydrolase (OPH). OPH enzyme was covalently bonded to a fluorescent probe, fluorescein isothiocyanate (FITC), and used as a biological recognition element. Under optimal experimental conditions, OPH monolayers were deposited onto the surface of silanized quartz slides as LB film and utilized as a bioassay for the detection of paraoxon. Two different methods were employed for detection of paraoxon: the fluorescence quenching of the fluorescence probe (FITC) covalently bonded to OPH and the UV–vis absorption spectrum of the paraoxon hydrolysis product. The UV–vis absorption measurement demonstrated a linear relationship between the absorbance at 400 nm and the concentration of paraoxon solutions over the range of 1.0 × 10 −7 –1.0 × 10 −5 M (0.27–27 ppm). By observing the FITC fluorescence quenching, the concentration of paraoxon can be detected as low as 10 −9 M (S/N = 3). The research described herein showed that the LB film bioassay had high sensitivity, rapid response time and good reproducibility.
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paper_title: Influence of surface-active compounds on the response and sensitivity of cholinesterase biosensors for inhibitor determination

paper_content:

The influence of non-ionogenic surfactants, i.e., Tween-20, Triton X-100 and PEG-10 000, on the response of cholinesterase-based potentiometric biosensors and their sensitivity towards reversible and irreversible inhibitors were investigated. Acetyl-and butyrylcholinesterases were immobilized on nylon, cellulose nitrate films and tracing paper and were introduced into an assembly of potentiometric biosensors. The effect of surface-active compounds depends on the hydrophilic properties and porosity of the enzyme support material and the inhibition mechanism. In the range 0.002–0.3% m/v the surfactants show a reversible inhibiting effect on biosensor response. At lower concentrations (down to 10–4% m/v) the surfactants alter the analytical characteristics of reversible and irreversible inhibitor determination. The use of surface-active additives improves the biosensor selectivity in multi-component media.
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paper_title: Fluorescence polarization immunoassay based on a monoclonal antibody for the detection of the organophosphorus pesticide parathion-methyl.

paper_content:

A fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody for the detection of parathion-methyl (PM) was developed and optimized. Fluorescein-labeled PM derivatives (tracers) with different structures were synthesized and purified by thin-layer chromatography. The influence of immunogen and tracer structures on the assay characteristics was investigated. PM concentration determinable by the FPIA ranged from 25 to 10000 ppb. The detection limit was 15 ppb. Methanol extracts of vegetable, fruit, and soil samples were diluted 1/10 for the analysis. Recovery in spiked samples averaged between 85 and 110%. The method developed is characterized by high specificity and reproducibility (CV ranged from 1.5 to 9.1% for interassay and from 1.8 to 14.1% for intra-assay). The FPIA method can be applied to the screening of food and environmental samples for PM residues without complicated cleanup.
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paper_title: Development of fluorescence polarization immunoassay for the detection of organophosphorus pesticides parathion and azinphos-methyl.

paper_content:

Organophosphorus Pesticides (OPPs) are a group of artificially synthesized substances used in farms to control pests and to enhance agricultural production. Although these compounds show preferential toxicity to insects, they are also toxic to humans and mammals by the same mode of action. ELISA now is an alternative method to detect OPPs. But, it must bear heterogenous properties, since several separation steps are needed during the ELISA method protocols. The FPIAs, which belong to homogenous assay, for determination of OPPs parathion and zainphos-methyl have been developed. The characteristics of Dep-EDF and PM-B-EDF tracers binding with antibodies A and D were investigated in the antibodies dilution experiments. The PM-B-EDF tracer combination with antibody D was selected to construct the standard curve for parathion detection. The IC50 value and the detection of limit were 1.96 mg/L and 0.179 mg/L, respectively, as shown in the standard curve. The tracers of PBM-EDF 2 and 3, which were chased from 4 PBM-EDF tracers, exhibited the good standard curves based on the MAb AZI-110. The FPIA constructed to analyze the azinphos-methyl showed the IC50 1.003 mg/L and detection limit 0.955 mg/L when PBM-EDF 2 was employed and the IC50 0.1487 mg/L and detection limit 0.150 mg/L were obtained when PBM-EDF 3 was used.
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paper_title: Determination of organophosphorus insecticides with a choline electrochemical biosensor

paper_content:

Abstract Organophosphorus insecticides have been determined with an amperometric hydrogen peroxide based choline biosensor. This class of pesticides inhibits cholinesterase enzymes which in the presence of their substrates produce choline. The decrease in activity of these enzymes is monitored by the choline sensor and is correlated to the concentration of pesticide present in solution. Pesticides such as paraoxon, parathion, methyl paraoxon and methyl parathion have been coupled with acetylcholine and butyrylcholine esterases. Results showed that although the enzyme activity of acetylcholinesterase (AChE) was higher than butyrylcholinesterase (BuChE), the lower specificity of BuChE resulted in a higher enzyme inhibition. The detection limit was less than 1 ppb with an incubation time of 120 min and 2 ppb when the incubation time was 30 min. This method has been applied to the analysis of pesticides in water samples. Results, compared with those obtained with a different analytical procedure (liquid/liquid extraction and GLC determination), demonstrated that our method is a good analytical choice to measure the total anticholinesterase activity in water samples.
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paper_title: Anticholinesterase activity of a new carbamate, heptylphysostigmine, in view of its use in patients with Alzheimer-type dementia

paper_content:

The anticholinesterase activity of a new carbamate, heptylphysostigmine, was studied in vitro. This compound is a competitive inhibitor of acetylcholinesterase (or true cholinesterase) having Ki = (1 +/- 0.5) X 10(-7) M. The inhibition was instantaneous at the onset and did not diminish with prolonged incubation of the drug and enzyme.
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paper_title: Design of fluorescent self-assembled multilayers and interfacial sensing for organophosphorus pesticides.

paper_content:

Abstract This paper details the fabrication of indole (ID) self-assembled multilayers (SAMs) and fluorescence interfacial sensing for organophosphorus (OP) pesticides. Quartz/APES/AuNP/ l -Cys/ID film was constructed on l -cysteine modified Quartz/APES/AuNP surface via electrostatic attraction between ID and l -cysteine. Cyclic voltammetry indicates that ID is immobilized successfully on the gold surface. Fluorescence of the Quartz/APES/AuNP/ l -Cys/ID film shows sensitive response toward OPs. The fluorescent sensing conditions of the SAMs are optimized that allow linear fluorescence response for methylparathion and monocrotophos over 5.97 × 10−7 to 3.51 × 10−6 g L−1 and 3.98 × 10−6 to 3.47 × 10−5 g L−1, with detection limit of 6.1 × 10−8 gL−1 and 3.28 × 10−6 gL−1, respectively. Compared to bulk phase detection, interfacial fluorescence sensing based on the SAMs technology shows higher sensitivity by at least 2 order of magnitude.
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paper_title: Use a Fluorescent Molecular Sensor for the Detection of Pesticides and Herbicides in Water

paper_content:

A fluorescent chemosensor based on modified �-cyclodextrin was used for the detection of pesticides and her- bicides in water. Binding constants, thermodynamic parameters and sensitivity factors were calculated and supported by AM1 semi-empirical method calculation. The results show clearly that a fluorescent chemical sensor based on modified � - cyclodextrin detects quantitatively the presence of pesticides or herbicides and allow a direct analysis of these pollutants as a new method of detection with limits of the order of ppm for the whole of the analytes.
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paper_title: Fluorescent sensors for organophosphorus nerve agent mimics.

paper_content:

We present a small molecule sensor that provides an optical response to the presence of an organophosphorus (OP)-containing nerve agent mimic. The design contains three key features: a primary alcohol, a tertiary amine in close proximity to the alcohol, and a fluorescent group used as the optical readout. In the sensor's rest state, the lone pair of electrons of the basic amine quenches the fluorescence of the nearby fluorophore through photoinduced electron transfer (PET). Exposure to an OP nerve agent mimic triggers phosphorylation of the primary alcohol followed rapidly by an intramolecular substitution reaction as the amine displaces the created phosphate. The quaternized ammonium salt produced by this cyclization reaction no longer possesses a lone pair of electrons, and a fluorescence readout is observed as the nonradiative PET quenching pathway of the fluorophore is shut down.
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paper_title: Fluorescent Detection of Chemical Warfare Agents: Functional Group Specific Ratiometric Chemosensors

paper_content:

Indicators providing highly sensitive and functional group specific fluorescent response to diisopropyl fluorophosphate (DFP, a nerve gas (G-agent) simulant) are reported. Nonemissive indicator 2 reacts with DFP to give a cyclized compound 2+A- that shows a high emission due to its highly planar and rigid structure. Very weak emission was observed by the addition of HCl. Another indicator based on pyridyl naphthalene exhibits a large shift in its emission spectrum after reaction with DFP, which provides for quantitative ratiometric detection.
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paper_title: Phosphoryl group transfer : evolution of a catalytic scaffold

paper_content:

It is proposed that enzymic phosphoryl-transfer reactions occur by concerted, step-wise, associative (phosphorane-intermediate) or dissociative (metaphosphate-intermediate) mechanisms, as dictated by the catalytic scaffold and the reactants. During the evolution of a phosphotransferase family, the mechanism of the phosphoryl-transfer reaction is in constant flux, potentially changing with each adaptation of the catalytic scaffold to a new phosphoryl-donor-acceptor pair. Phosphotransferases of the recently discovered haloacid dehalogenase superfamily of enzymes, one of the largest and most ubiquitous of the phosphotransferase families characterized to date, are described in the context of the co-evolution of the catalytic scaffold and mechanism.
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paper_title: Dual colorimetric and electrochemical sensing of organothiophosphorus pesticides by an azastilbene derivative

paper_content:

Abstract We have investigated the optical and electrochemical changes of the azastilbene, dimethyl-[4-(2-quinolin-2-yl-vinyl)-phenyl]-amine (DQA), with four organothiophosphorus (OTP) pesticides: ethion, malathion, parathion, and fenthion. Significant changes in UV–visible absorbance wavelength and in electrochemical signals indicate the effectiveness of DQA as an OTP sensor.
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paper_title: Dual optical and electrochemical saccharide detection based on a dipyrido[3,2-a:2'3'-c]phenazine (DPPZ) ligand

paper_content:

We report a new molecular sensor based on dipyrido[3,2-a:2′3′-c]phenazine (DPPZ) functionalized with boronic acid groups. The sensor binds to saccharides and upon binding results in changes in fluorescence intensity as well as cathodic shifts in the sensor’s formal potential. The ability of the new DPPZ-based sensor to provide both electrochemical and optical signal outputs demonstrates the viability of this family of molecules to be developed as dual-signal detectors. Measurements to determine the stability constants with four saccharides are shown.
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paper_title: Dual signal transduction mediated by a single type of olfactory receptor expressed in a heterologous system

paper_content:

Controversy exists over the relationship between the cAMP and IP 3 pathways in vertebrate olfactory signal transduction, as this process is known to occur by either of the two pathways. Recent studies have shown that a single olfactory neuron responds to both cAMP- and IP 3 -producing odorants, suggesting the existence of an olfactory receptor protein that can recognize both ligands. In this study we found that the rat olfactory receptor 17, stably expressed in HEK-293 cells, triggers the cAMP pathway upon stimulation by a specific odorant (octanal) at concentrations lower than 10 - 4 M; however, the receptor triggers both pathways at higher concentrations. This indicates that a single olfactory receptor, stimulated by a single pathway-inducing odorant, can evoke both pathways at high odorant concentrations. Using this heterologous system, both the dose-dependent response and receptor 17 specificity were analyzed. The dose-dependent Ca 2 + response curve, which also includes the release of Ca 2 + ions from internal stores at high odorant concentrations, was not monotonous, but had a local maximum and minimum with 10 - 1 0 and 10 - 7 M octanal, respectively, and reached a plateau at 10 - 2 M octanal. The specificity of the 17 receptor was lower when exposed to higher concentrations of odorants.
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paper_title: Protonation dependent electron transfer in 2-styrylquinolines

paper_content:

Abstract The absorption and emission spectra for 4′-substituted-2-trans-styrylquinoiline ( X = NMe 2 , 1 ; H , 2 ; CN , 3 ; NO 2 , 4 ) and 4′-N,N-dimethylamino-2-trans-styrylnaphthalene 5 were studied in various solvents and at various acid concentrations. Monoprotonated or doubly protonated forms of 1 are present depending on the acid concentration. Excited state deprotonation of the doubly protonated form of 1 is observed in aprotic dichloromethane solvent. This excited state deprotonation process can be prevented by introducing protic methanol to the aprotic solvent media.
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Title: Fluorescent Chemosensors for Toxic Organophosphorus Pesticides: A Review

Section 1: Introduction
Description 1: Provide an overview of the environmental impact of organophosphorus pesticides, the necessity for monitoring these compounds, and the advantages of using fluorescent chemosensors.

Section 2: Structure of Organophosphorus Compounds
Description 2: Detail the chemical structure of organophosphorus pesticides, including the different types and their basic structural components.

Section 3: OP Compounds and Their Toxicity
Description 3: Discuss the toxic effects of organophosphorus compounds on human health and the environment, including their mechanisms of action and routes of exposure.

Section 4: Advances in Detection of OP compounds
Description 4: Describe the various advanced techniques developed for the detection of organophosphorus compounds, emphasizing traditional and newer methods.

Section 5: Fluorescence-based Biosensors for OP Compounds
Description 5: Review the development and applications of fluorescence-based biosensors specifically designed for detecting organophosphorus compounds.

Section 6: Fluorescence-based Chemosensor Detection Methods
Description 6: Discuss the innovative methods for the detection of organophosphorus compounds using fluorescent chemosensors, detailing specific examples and their mechanisms.

Section 7: Sensors with Multiple Modes of Signal Transduction
Description 7: Present multimodal sensing technologies and their benefits in minimizing false positives in the detection of organophosphorus pesticides.

Section 8: Future Perspectives
Description 8: Outline the future directions and improvements needed for developing more efficient, selective, and robust fluorescent chemosensors for organophosphorus pesticides.