Schiff base – Zn2+ ion combo as ‘pick and degrade’ probe for selected organophosphorus chemical weapon mimics and flame retardant analog: Detoxification of fruits and vegetables in aqueous media

Novel Ultrasensitive Fluorescent Probe for Bioimaging Carboxylesterase and Detecting Pesticide Residues in Foods

Pesticide residues pose a significant threat to food safety and human health, necessitating the development of novel detection tools. Pesticides can inhibit the activity of certain biological enzymes, so enzyme inhibition is one of the methods of pesticide detection. In this study, we developed a novel near-infrared fluorescent probe named TCFCl-CES based on the tricyanofuran structure, for ultrasensitive detection of carboxylesterase (CES). TCFCl-CES exhibits strong and stable fluorescence, excellent specificity. Notably, the fluorescence intensity of TCFCl-CES shows a linear relationship with CES concentration, achieving an exceptionally low detection limit of 4.41 × 10-5 u/mL. This ultrasensitive probe can also effectively detect pesticide residues in vegetables and monitor CES activity in cells and liver tissues. TCFCl-CES stands out for its rapid and accurate detection capabilities, making it an essential tool for accurately monitoring pesticide residue. It also has great potential for tracking CES activity in biological systems. Additionally, it offers a robust solution for food safety and improving pesticide residue analysis.

Highly selective and sensitive chromogenic recognition of sarin gas mimicking diethylchlorophosphate

The high-level toxic effects of organophosphate (OP) nerve agents severely threaten national security and public health. Generating trustworthy, accurate methods for quickly identifying these poisonous chemicals is urgently necessary. In this study, we have presented an azine-based colorimetric sensor (HBD) for the highly sensitive and selective identification of poisonous sarin gas surrogate diethylchlorophosphate (DCP). Our introduced sensor shows a purple color in contact with DCP, which is fully reversible upon the addition of triethylamine (TEA). The detection limit of our sensor for the toxic nerve agent mimic DCP is in the μM range. We have fabricated a test kit to verify the capability of HBD for on-the-spot identification of DCP to execute its practical use. To prove that HBD is an effective chemosensor, dip-stick investigation was conducted to detect DCP in the vaporous stage in the presence of different OPs, inorganic phosphates (IPs), and many other deadly analytes. A cellphone-based display method was also undertaken for on-the-spot recognition and measurement of DCP in isolated regions.

A benzoxazole-based turn-on fluorosensor for rapid and sensitive detection of sarin surrogate, diethylchlorophosphate

A benzoxazole-based fluorosensor (IMP) has been synthesized and employed for the selective and sensitive detection of sarin surrogate, diethylchlorophosphate (DCP) in solution, and gas phase, respectively. Remarkable turn-on fluorescence is observed due to the introduction of DCP in the solution of IMP because of inhibition of the intramolecular charge transfer process and disruption of the excited state intramolecular proton transfer (ESIPT) mechanism. The synthesized IMP-based fluorescence sensor exhibits excellent selectivity, high sensitivity, and a wide linear range of 15-60 μM with a detection limit of 44 nM. Low-intense to highly intensified visible violet color could be seen by the naked eye under a portable 365 nm UV lamp due to the addition of DCP in the solution of IMP. IMP-stained paper strips-based test kit experiment has been demonstrated to detect traces of DCP in stockpiles of related analytes. A dip-stick experiment for the detection of DCP vapor has also been demonstrated. The effectiveness of IMP in detecting DCP established that it might be used as a signal tool for real sample analysis.

A PET and ESIPT-communicated ratiometric, turn-on chromo-fluorogenic sensor for rapid and sensitive detection of sarin gas mimic, diethylchlorophosphate

Fast and precise identification of toxic G-series nerve agents in the solution and vapor phase is urgently needed to save human beings from unwanted wars and terrorist attacks, which is challenging to execute practically. In this article, we have designed and synthesized a sensitive and selective phthalimide-based chromo-fluorogenic sensor, DHAI, by a simple condensation process that shows ratiometric and turns on chromo-fluorogenic behavior towards Sarin gas mimic diethylchlorophosphate (DCP) in liquid and vapor phases, respectively. A colorimetric change, from yellow to colorless, is observed in the DHAI solution due to the introduction of DCP in daylight. A remarkable cyan color photoluminescence enhancement is noticed in the presence of DCP in the DHAI solution, which is observable to the naked under a portable 365 nm UV lamp. The mechanistic aspects of the detection of DCP by employing DHAI have been revealed by time-resolved photoluminescence decay analysis and ¹H NMR titration investigation. Our probe DHAI exhibits linear photoluminescence enhancement from 0 to 500 μM with a detection limit of nanomolar range from non-aqueous to semi-aqueous media. For practical utility, a DHAI-stained test kit employing Whatman-41 filter paper has been fabricated and used as a portable and displayable photonic device for on-site detection of Sarin gas surrogate, DCP. Also, a dip-stick experiment has been demonstrated to identify the vapor of Sarin gas mimics DCP colorimetrically and fluorometrically. The concentrations of DCP in various water samples have been evaluated with the help of a standard fluorescence curve for real sample analysis.

In-situ generation of fluorescent silica nano-aggregates of silatranyl appended furfural Schiff base and its application to the spectrofluorimetric analysis of phenolic brominated flame retardants in aqueous medium

A silatranyl appended furfural Schiff base (Silt-FUR) has been synthesized and characterized by spectroscopic techniques, elemental analysis and mass spectrometry. The dissolution of Silt-FUR in methanol-water (90:10 v/v) results in the formation of fluorescent nano-aggregates due to the hydrolysis of the silatranyl ring. The formation of nano-aggregates has been confirmed by dynamic light scattering, scanning electron microscopy and transmission electron microscopy. The nano-aggregates exhibit quenching of fluorescence in the presence of phenolic brominated flame retardants such as 3,3',5,5'-tetrabromobisphenol A, 2,4-dibromophenol, 2,4,6-tribromophenol, and pentabromophenol. Density-Functional Theory and NMR titration suggest that acid-base pair formation between azomethinic functionality and flame retardants is the main cause of quenching of fluorescent signal as it causes photoinduced electron transfer. Due to the excellent spectrofluorimetric response of Silt-FUR nano-aggregates to detect brominated phenols, a spectrofluorimetric method has been standardized for the quantification of brominated flame retardants. The detection limit for pentabromophenol obtained is 0.432 µM under optimal experimental conditions, and the linear range of the determination is 0.0495-1.35 µM. Thus, the in-situ generation of nano-aggregates offers a user-friendly method for the detection, quantification and extraction of the brominated phenols with exceptionally high sensitivity and selectivity for pentabromophenol.

A Double-Site Chemodosimeter for Selective Fluorescence Detection of a Nerve Agent Mimic

A novel two-site chemodosimeter (SWJT-4) based on fluorescein skeleton to detect diethyl chlorophosphate (DCP) was designed and synthesized. It is a turn-on fluorescent probe for DCP with good selectivity and obvious color change in aqueous solution. Interestingly, the two oxime groups of SWJT-4 as dual response sites initiated different reactions with DCP to form a cyano group and an isoxazole ring, respectively. The corresponding mechanism was confirmed by 1H NMR, MS and DFT calculation. Moreover, SWJT-4 could be used as a fluorescent test paper to detect DCP vapor.

A sensitive bio-barcode immunoassay based on bimetallic Au@Pt nanozyme for detection of organophosphate pesticides in various agro-products

Organophosphate pesticides (OPs) are often used as insecticides and acaricides in agriculture, thus improving yields. OP residues may pose a serious threat, duetoinhibitionof the enzymeacetylcholinesterase(AChE). Therefore, a competitive bio-barcode immunoassay was designed for simultaneous quantification of organophosphate pesticide residues using AuNP signal amplification technology and Au@Pt catalysis. The AuNP probes were labelled with antibodies and corresponding bio-barcodes (ssDNAs), MNP probes coated with ovalbumin pesticide haptens and Au@Pt probes functionalized with the complementary ssDNAs were then prepared. Subsequently, pesticides competed with MNP probes to bind the AuNP probes. The recoveries of the developed assay were ranged from 71.26 to 117.47% with RSDs from 2.52 to 14.52%. The LODs were 9.88, 3.91, and 1.47 ng·kg^-1, for parathion, triazophos, and chlorpyrifos, respectively. The assay was closely correlated with the data obtained from LC-MS/MS. Therefore, the developed method has the potential to be used as an alternative approach for detection of multiple pesticides.

Detection of organophosphorus pesticides by nanogold/mercaptomethamidophos multi-residue electrochemical biosensor

Based on the successful synthesis of mercaptomethamidophos as a substrate, a novel nanogold/mercaptomethamidophos multi-residue electrochemical biosensor was designed and fabricated by combining nanoscale effect, strong Au-S bonds as well as interaction between acetylcholinesterase (AChE) and mercaptomethamidophos, which can simultaneously detect 11 kinds of organophosphorus pesticides (OPPs) and total amount of OPPs using indirect competitive method. Electrochemical behavior of the modified electrode was characterized by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The AChE concentration and incubation time were optimized at 37.4 °C to achieve the best detection effect. This biosensor exhibits excellent electrochemical properties with a wider linear range of 0.1 ~ 1500 ng·mL^-1, lower detection limit of 0.019 ~ 0.077 ng·mL^-1, better stability and repeatability, which realizes the rapid detection of total amount of OPPs, and can simultaneously detect a large class of OPPs rather than one kind of OPP. Two OPPs (trichlorfon, dichlorvos) were detected in actual samples of apple and cabbage and achieved satisfactory test results.

Construction of a red emission fluorescent protein chromophore-based probe for detection of carboxylesterase 1 and carbamate pesticide in culture cells

Designing fluorescent probe for detecting carboxylesterase 1 is remains challenging. Herein, a red emission human carboxylesterase 1 (CES1) probe (CAE-FP) was synthesized based on fluorescent protein chromophore. Probe CAE-FP can specific detect human CES1 with high selectively. The fluorescence quantum yield was calucated as 0.19. The carboxylic acid ester in CAE-FP could be easily hydrolyzed by CES1 under physiological conditions, and this process could induce the obvious fluorescence signal in red emission region. The detection limit of CES1 was calculated as 84.5 ng/mL. Due to the biological detoxification mechanism of carboxylesterase and the obvious inhibitory effect of pesticides on its activity, CAE-FP was applied to detect carbamate pesticide and have achieved good application results. Since fluorescent protein chromophore has excellent biocompatibility, probe CAE-FP with good cell membrane permeable and was successfully applied to monitor the real activities of CES1 in living cells. In summary, this is one of the few reported fluorescent probes that can specific detect the real-time activity of CES1 in biological samples. Besides, we first applied the fluorescent protein chromophore to construct the specific target enzyme probe. This work would contribute to further investigate CES1-associated physiological and pathological processe.