A sensitive chemiluminescence enzyme immunoassay based on molecularly imprinted polymers solid-phase extraction of parathion

Molecularly imprinted polymers for environmental adsorption applications

Molecular imprinting polymers (MIPs) are synthetic materials with pores or cavities to specifically retain a molecule of interest or analyte. Their synthesis consists of the generation of three-dimensional polymers with specific shapes, arrangements, orientations, and bonds to selectively retain a particular molecule called target. After target removal from the binding sites, it leaves empty cavities to be re-occupied by the analyte or a highly related compound. MIPs have been used in areas that require high selectivity (e.g., chromatographic methods, sensors, and contaminant removal). However, the most widely used application is their use as a highly selective extraction material because of its low cost, easy preparation, reversible adsorption and desorption, and thermal, mechanical, and chemical stability. Emerging pollutants are traces of substances recently found in wastewater, river waters, and drinking water samples that represent a special concern for human and ecological health. The low concentration in which these pollutants is found in the environment, and the complexity of their chemical structures makes the current wastewater treatment not efficient for complete degradation. Moreover, these substances are not yet regulated or controlled for their discharge into the environment. According to the literature, MIPs, as a highly selective adsorbent material, are a promising approach for the quantification and monitoring of emerging pollutants in complex matrices. Therefore, the main objective of this work was to give an overview of the actual state-of-art of applications of MIPs in the recovery and concentration of emerging pollutants.

Development of a Reliable ic-ELISA with a Robust Antimatrix Interference Capability Based on QuEChERS Technology for the Rapid Detection of Zearalenone in Edible and Medical Coix Seeds and Subsequent Risk Assessments

Indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) is an ideal immunoassay method for large-scale screenings to detect mycotoxin contaminants. However, the matrix effect of complicated samples has always been challenging when performing immunoassays, as it leads to false-positive or negative results. In this study, convenient QuEChERS technology combined with optimizing the dilution solvent was ingeniously used to eliminate interference from the sample matrix to greatly improve the detection accuracy, and reliable ic-ELISAs for the two official tolerance levels of 60 and 500 μg/kg were developed to screen zearalenone (ZEN) in edible and medical coix seeds without any further correction. Then, the 122 batches of coix seeds were determined, and the positive rate was up to 97.54%. The contaminated distribution was further analyzed, and risk assessment was subsequently performed for its edible and medical purposes. The findings indicated that consumption of coix seeds with higher ZEN contamination levels may cause adverse health effects for both medical and edible consumption in the adult population; even under the condition of average contamination level, ZEN from coix seeds was the more prominent contributor to the total risk compared to other sources when used as food; thus, effective prevention and control should be an essential topic in the future.

Use of molecular imprinted polymers as sensitive/selective luminescent sensing probes for pesticides/herbicides in water and food samples

As non-biological molecules, molecular imprinted polymers (MIPs) can be made as antibody mimics for the development of luminescence sensors for various targets. The combination of MIPs with nanomaterials is further recognized as a useful option to improve the sensitivity of luminescence sensors. In this work, the recent progresses made in the fabrication of fluorescence, phosphorescence, chemiluminescence, and electrochemiluminescence sensors based on such combination have been reviewed with emphasis on the detection of pesticides/herbicides. Accordingly, the materials that are most feasible for the detection of such targets are recommended based on the MIP technologies.

Immunoassay technology: Research progress in microcystin-LR detection in water samples

Increasing global warming and eutrophication have led to frequent outbreaks of cyanobacteria blooms in freshwater. Cyanobacteria blooms cause the death of aquatic and terrestrial organisms and have attracted considerable attention since the 19th century. Microcystin-LR (MC-LR) is one of the most typical cyanobacterial toxins. Therefore, the fast, sensitive, and accurate determination of MC-LR plays an important role in the health of humans and animals. Immunoassay refers to a method that uses the principle of immunology to determine the content of the tested substance in a sample using the tested substance as an antigen or antibody. In analytical applications, the immunoassay technology could use the specific recognition of antibodies for MC-LR detection. In this review, we firstly highlight the immunoassay detection of MC-LR over the past two decades, including classical enzyme-link immunosorbent assay (ELISA), modern immunoassay with optical signal, and modern immunoassay with electrical signal. Among these detection methods, the water environment was used as the main detection system. The advantages and disadvantages of the different detection methods were compared and analyzed, and the principles and applications of immunoassays in water samples were elaborated. Furthermore, the current challenges and developmental trends in immunoassay were systematically introduced to enhance MC-LR detection performance, and some critical points were given to deal with current challenges. This review provides novel insight into MC-LR detection based on immunoassay method.

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.

A dual-signal sensor for the analysis of parathion-methyl using silver nanoparticles modified with graphitic carbon nitride

A highly sensitive and selective method was developed for both UV-vis spectrophotometric and fluorimetric determination of organophosphorus pesticides (OPs). This method used silver nanoparticles (AgNPs) modified with graphitic carbon nitride (g-C3N4). The AgNPs reduced the fluorescence intensity of g-C3N4. Acetylthiocholine (ATCh) could be catalytically hydrolyzed by acetylcholinesterase (AChE) to form thiocholine, which induces aggregation of the AgNPs. This aggregation led to the recovery of the blue fluorescence of g-C3N4, with excitation/emission peaks at 310/460 nm. This fluorescence intensity could be reduced again in the presence of OPs because of the inhibitory effect of OPs on the activity of AChE. The degree of reduction was found to be proportional to the concentration of OPs, and the limit of fluorometric detection was 0.0324 μg/L (S/N = 3). In addition, the absorption of the g-C3N4/AgNPs at 390 nm decreased because of the aggregation of the AgNPs, but was recovered in presence of OPs because of the inhibition of enzyme activity by OPs. This method was successfully applied to the analysis of parathion-methyl in real samples.

Solid-State Membrane Sensors Based on Man-Tailored Biomimetic Receptors for Selective Recognition of Isoproturon and Diuron Herbicides

Solid-contact ion-selective electrodes (SC-ISEs) have shown great potential for routine and portable ion detection. The introduction of nanomaterials as ion-to-electron transducers and the adoption of different performance-enhancement strategies have significantly promoted the development of SC-ISEs. Herein, new solid-contact ion-selective electrodes, along with the implementation of multiwalled carbon nanotubes (MWCNTs) as ion-to-electron transducers and potassium tetrakis (p-chlorophenyl) borate (KTpClB) as lipophilic ionic additives, were presented for the detection of isoproturon (IPU) and diuron (DU) herbicides. Molecularly imprinted polymers (MIPs), with special molecule recognition properties for isoproturon (IPU) and diuron (DU), were prepared, characterized, and introduced as sensory recognition materials in the presented electrodes. Sensors revealed a near-Nernstian response for both isoproturon (IPU) and diuron (DU) with slopes of 53.1 ± 1.2 (r² = 0.997) and 57.2 ± 0.3 (r² = 0.998) over the linear ranges of 2.2 × 10^-6-1.0 × 10^-3 M and 3.2 × 10^-6-1.0 × 10^-3 M with detection limits of 8.3 × 10^-7 and 1.4 × 10^-6 M, respectively. The response time of the presented sensors was found to be <5 s and the lifetime was at least eight weeks. The sensors exhibited good selectivity towards isoproturon (IPU) and diuron (DU) in comparison with some other herbicides, alkali, alkaline earth, and heavy metal ions. The presented sensors were successfully applied for the direct determination of isoproturon (IPU) and diuron (DU) in real water samples.

Cost-Effective Potentiometric Platforms Modified with Multi-Walled Carbon Nanotubes (MWCNTs) and Based on Imprinted Receptors for Fluvoxamine Assessment

A simple, efficient and reliable analytical method was developed and used for the determination of the fluvoxamine drug (FLV) in pharmaceutical preparations and biological fluids. The method is based on the cost-effective screen-printed platform for the potential transduction of the drug. Host-tailored molecular imprinting polymer (MIP) was integrated with the potentiometric platform as a recognition receptor, in which FLV, acrylamide (AAm), ethylene glycol dimethacrylate (EGDMA) and acetonitrile were used as a template, functional monomer, cross-linker, and solvent, respectively. MIP particles were dispersed in plasticized poly (vinyl chloride) (PVC) and the membrane was drop-casted on carbon screen-printed electrode. The MIP, in addition to non-imprinted polymers (NIP), was characterized and the binding experiment revealed high affinity and adsorption capacity of MIP towards FLV. The proposed sensor displayed near-Nernstian cationic slope of 55.0 ± 0.8 mV/decade (r² = 0.999) with a low detection limit of 4.8 × 10⁻⁶ mol/L over a wide pH range (3.0–8.5). The electrochemical features of the proposed sensors including electrochemical impedance spectroscopy (EIS) and chronopotentiometry measurements (CP) in the presence of multi-walled carbon nanotubes (MWCNTs) as a solid contact transducer were also investigated. The applications of the proposed sensor for the determination of FLV in different dosage forms with recovery values (98.8%–101.9%) and (97.4%–101.1%), respectively compared with the reference HPLC method with acceptedFandt-student tests values at the 95% confidence level.

Competitive Bio-Barcode Immunoassay for Highly Sensitive Detection of Parathion Based on Bimetallic Nanozyme Catalysis

A competitive sensitive bio-barcode immunoassay based on bimetallic nanozyme (Au@Pt: gold@platinum) catalysis has been designed for the detection of the pesticide parathion. Gold nanoparticles (AuNPs) were modified with single-stranded thiol oligonucleotides (ssDNAs) and monoclonal antibodies (mAbs) to form AuNP probes; magnetic nanoparticles (MNPs) were coated with ovalbumin (OVA)-parathion haptens as MNP probes, and bimetallic nanozyme (Au@Pt) nanoparticles functionalized with the complementary thiolated ssDNA were used as Au@Pt probes. The Au@Pt probes reacted with the AuNP probes through complementary base pairing. Further, parathion competed with MNP probes to bind the mAbs on the AuNP probes. Finally, the complex system was separated by a magnetic field. The released Au@Pt probes catalyzed a chromogenic system consisting of teramethylbenzidine (TMB). The bimetallic nanozyme-based bio-barcode immunoassay was performed on rice, pear, apple, and cabbage samples to verify the feasibility of the method. The immunoassay exhibited a linear response from 0.01 to 40 μg·kg^-1, and the limit of detection (LOD) was 2.13 × 10^-3 μg·kg^-1. The recoveries and relative standard deviations (RSDs) ranged from 73.12 to 116.29% and 5.59 to 10.87%, respectively. The method was found to correlate well with data obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In conclusion, this method exhibits potential as a sensitive alternative method for the detection of a variety of pesticides, ensuring the safety of fruits and vegetables in agriculture.

Enhancing the Sensitivity of the Bio-barcode Immunoassay for Triazophos Detection Based on Nanoparticles and Droplet Digital Polymerase Chain Reaction

An ultrasensitive bio-barcode competitive immunoassay method based on droplet digital polymerase chain reaction (ddPCR) was developed for the determination of triazophos. Gold nanoparticles (AuNPs) were coated with monoclonal antibodies (mAbs) and complementary double-stranded DNA (dsDNA), which included bio-barcode DNA and thiol-capped DNA. Magnetic nanoparticle (MNP) probes were constructed by modifying the MNPs with ovalbumin-hapten conjugates (OVA-hapten). The target pesticide and OVA-hapten on the surface of the MNP probes competed with the AuNP probes simultaneously, and then the bio-barcode DNA was released for quantification by ddPCR. The concentration of released DNA was inversely proportional to the concentration of pesticide to be tested. Under the optimum conditions, the competitive immunoassay exhibited a wide linear range of 0.01-20 ng/mL and a low detection limit of 0.002 ng/mL. Spike recovery tests were carried out using apple, rice, cabbage, and cucumber samples to verify the feasibility of the method. The recovery and relative standard deviations (RSDs) of the technique ranged from 76.9 to 94.4% and from 10.8 to 19.9%, respectively. To further validate the results, a linear correlation analysis was performed between the proposed method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Consequently, the bio-barcode immunoassay based on nanoparticles and ddPCR, an ultrasensitive method, showed great potential for the determination of target pesticides in real samples.

Colorimetric bio-barcode immunoassay for parathion based on amplification by using platinum nanoparticles acting as a nanozyme

A competitive bio-barcode immunoassay is described for the trace detection of parathion in water, pear, cabbage, and rice samples. It is based on amplification by platinum nanoparticle acting as a nanozyme. Gold nanoparticles (AuNPs) were modified with (a) monoclonal antibodies (mAbs) against parathion, and (b) thiolated single-stranded DNA (ssDNA) oligonucleotides. Magnetic nanoparticles (MNPs) were functionalized with ovalbumin coupled with parathion hapten. Parathion and its hapten compete with mAbs on the surface of the AuNPs. Subsequently, the platinum nanoparticles (PtNPs) probe, which was functionalized with the complementary thiolated ssDNA (C-ssDNA), was added to the reaction mixture for the detection of parathion. The signal was catalytically amplified by coupling with platinum nanozyme using teramethylbenzidine and H₂O₂ as the chromogenic system. The immunoassay has a linear range that extends from 0.01-50 μg·L^-1, and the limit of detection is 2.0 × 10^-3 μg·L^-1. The recoveries and relative standard deviations (RSDs) ranged from 91.1-114.4% and 3.6-15.8%, respectively. The method correlates well with data obtained by gas chromatography-tandem mass spectrometry (GC-MS/MS). Graphical abstract The parathion and the magnetic nanoparticles (MNPs) labelled with hapten-OVA competitively reacted to AuNPs modified with mAbs and thiolated DNA for the detection of parathion. The signal was catalyzed by platinum nanozyme. The limit of detection for parathion is 2.0 ng·L^-1.

A chemiluminescence biosensor for lysozyme detection based on aptamers and hemin/G-quadruplex DNAzyme modified sandwich-rod carbon fiber composite

In our work, aptamers and hemin/G-quadruplex DNAzyme modified sandwich-rod graphene quantum dots @ graphene oxide @ carbon fiber composite (DNAzyme/L-Apt/GQDs@GO@CF) was successfully prepared for sensitive and selective chemiluminescence (CL) detection of lysozyme (LZM). Initially, GQDs@GO@CF was successfully prepared and characterized. Lysozyme aptamers (L-Apt) as a recognition element and hemin/G-quadruplex DNAzyme (DNAzyme) as a catalyst of luminal - H₂O₂ were modified on the surface of GQDs@GO@CF, sequentially. The immobilization properties of GQDs@GO@CF to L-Apt and the adsorption properties of L-Apt/GQDs@GO@CF to DNAzyme were also researched, respectively. Then, the modified sandwich-rod carbon fiber composite was applied to the construction of CL biosensor for LZM detection. When LZM existed, DNAzyme would be released from the surface of L-Apt/GQDs@GO@CF and catalyzed the reaction of luminal - H₂O₂. Under optimized conditions, the CL biosensor for LZM detection showed wide linear range of 2.64 × 10^-10 to 6.6 × 10^-8 g/L and low detection limit of 1.25 × 10^-11 g/L (3δ). Finally, the CL biosensor was successfully used for LZM detection in human urine samples and illustrated the potential application in pratical samples.

A biocompatible high surface area ZnO-based molecularly imprinted polymer for the determination of meloxicam in water media and plasma

Ultrasound-assisted solid-phase microextraction (SPME) by a functionalized high surface area ZnO nanoparticle (NP)-based molecularly imprinted polymer (MIP) followed by UV-Vis spectrophotometry was described as a selective, economic and rapid technique which was established for the extraction and preconcentration of meloxicam (MEL) in water media and plasma.

Ultrasonically synthesis of Mn- and Cu- @ ZnS-NPs-AC based ultrasound assisted extraction procedure and validation of a spectrophotometric method for a rapid preconcentration of Allura Red AC (E129) in food and water samples

This study is devoted on Allura Red as food colorant preconcentration and determination in beverage, fruit juice and drink water samples is based on usage of Mn- and Cu- @ ZnS-NPs-AC as new sorbent for ultrasound-assisted-dispersive solid-phase microextraction (UA-DSPME) combined with ultraviolet-visible spectrophotometric based method (UV-Vis). Contribution of volume of eluent, pH, sorbent mass and sonication time on response following conduction of 28 experiments were optimized and investigated while their significantly justified according to p-value. Values of "Prob > F" less than 0.0500 is proportional with their significant influence on recovery of analyte. Under the optimum conditions 0.14 mL of THF; pH of 2.5; 8 mg of sorbent and 3 min sonication time guide and help achievement of limit of quantification (LOQ) and limit of detection (LOD) of 6.08 and 20.26 ng mL^-1, respectively. The accuracy of method was validated according to calculation of recovery following spiking 400 and 600 ng mL^-1 to blank solution and recovery as more reliable indication of accuracy 93.41 and 102.17% recoveries with RSD < 3.5%, which demonstrate the successful applicability of present method for real sample analysis. The maximum sorbent capacity was 50.0 mg g^-1 based on Langmuir isotherm as best model with high correlation coefficient. Combination of UA-DSPME and UV-Vis lead to higher sensitivity and lower cost for accurate and repeatable monitoring of Allura Red level in beverage, fruit juice and drink water samples with acceptable recovery and reasonable RSD%.

Chitosan-Based Surface Molecularly Imprinted Polymer Microspheres for Sustained Release of Sinomenine Hydrochloride in Aqueous Media

The surface molecular imprinting technique has been proposed as a prospective strategy for template molecule recognition and separation by devising the recognition sites on the surface of imprinted materials. The purpose of this study was to establish a novel drug delivery system which was developed by surface molecular imprinting method using β-cyclodextrin (β-CD)-grafted chitosan (CS) (CS-g-β-CD) microspheres as matrix and sinomenine hydrochloride (SM) as the template molecule. By adjusting the amount of functional monomer and cross-linking agent, we got the more excellent adsorption of CS-g-β-CD molecularly imprinted polymers (MIPs-CS-g-β-CD). When the amount of functional monomer was 6 mmol and cross-linking agent was 20 mmol, the maximum binding capacity of MIPs and non-imprinted polymers (NIPs) was 55.9 mg/g and 37.2 mg/g, respectively. The results indicated that the recognition of SM with MIPs was superior to NIPs. The adsorption isotherms of MIPs-CS-g-β-CD indicated that the adsorption behavior fitted better to the Langmuir model, which showed that the adsorption process of polymer was monomolecular layer. In in vitro drug release studies, the accumulative release amount of MIPs-CS-g-β-CD was up to 78% within 24 h. MIPs exhibited an excellent controlled SM release profile without burst release and the mechanism of SM release was shown to conform to non-Fick diffusion. Therefore, MIPs-CS-g-β-CD were successfully applied to extraction of SM and used as the materials for drug delivery system.