A core-shell surface magnetic molecularly imprinted polymers with fluorescence for λ-cyhalothrin selective recognition

A magnetic molecular imprinting-based fluorescence probe for sensitive and selective detection of 2,4-D herbicide

A new magnetic molecular imprinting-based turn-on fluorescence probe (Fe3 O4 NPs@SiO2 @NBD@MIPs) has been synthesized via a facile sol-gel polymerization for the detection of 2,4-dichlorophenoxyacetic acid (2,4-D). Based on the photoinduced electron transfer (PET) of nitrobenzoxadiazole (NBD), 2,4-D can be recognized by enhancement of NBD fluorescence. With the presence of Fe3 O4 in the core of the probe, this sensor can also be reused many times using magnetic aggregation methods. After the addition of various concentrations of 2,4-D, the fluorescence peak at 530 nm (excitation of 468 nm) increased linearly ranging from 0.1 to 3 μM with a detection limit of 0.023 μM. This sensing system is believed to be available for detecting 2,4-D in real samples, with high recovery rates ranging from 94% to 108% for three spike levels of 2,4-D with precisions below 5%.

Recent Advances in Nanoparticle-Based Optical Sensors for Detection of Pesticide Residues in Soil

The excessive and unreasonable use of pesticides has adversely affected the environment and human health. The soil, one of the most critical natural resources supporting human survival and development, accumulates large amounts of pesticide residues. Compared to traditional spectrophotometry analytical methods, nanoparticle-based sensors stand out for their simplicity of operation as well as their high sensitivity and low detection limits. In this review, we focus primarily on the functions that various nanoparticles have and how they can be used to detect various pesticide residues in soil. A detailed discussion was conducted on the properties of nanoparticles, including their color changeability, Raman enhancement, fluorescence enhancement and quenching, and catalysis. We have also systematically reviewed the methodology for detecting insecticides, herbicides, and fungicides in soil by using nanoparticles.

Dietary powder and molecular imprinted polymer nanoencapsulated sodium propionate to enhance growth performance, digestive enzymes activity, antioxidant defense, and mucosal immune response in African cichlid (Labidochromis lividus) fingerlings

This study was conducted to examine the effects of powder sodium propionate (P-SP) and SP-loaded molecular imprinted polymer (MIP) nanoparticles (MIP-SP NPs) on the growth, skin mucosal immune parameters, and digestive and liver enzymes activities of African cichlid (Labidochromis lividus) fingerlings. Fish with an average weight of 500±2 mg were stocked into 12 experimental units and fed on experimental diets prepared by supplementing the basal diet (control) with MIP NPs, P-SP (5 g SP Kg-1 of dry diet), and MIP-SP NPs for 8 weeks. The findings demonstrated that growth indices improved in the MIP-SP NPs followed by the P-SP dietary group compared to the control groups (P<0.05). The activity of digestive enzymes of lipase, trypsin, protease, and alkaline phosphatase was higher in the fish fed SP-supplemented diets than in the controls (P<0.05). The protease and lipase activities in the MIP-SP NPs dietary group increased by 29.33% and 48.81% compared to the control, respectively (P<0.05). In addition, the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of liver tissue decreased in the SP dietary groups, while the catalase (CAT), superoxide dismutase (SOD), and alkaline phosphatase (ALP) levels increased compared to the control groups (P<0.05). The highest SOD and ALP levels were observed in the fish fed on the MIP-SP NPs-supplemented diet (P<0.05). Furthermore, the skin mucosal immune indices including, alternative haemolytic complement activity (ACH50), lysozyme, and total immunoglobulin (Ig) levels increased in the MIP-SP NPs and P-SP dietary groups compared to the controls (P<0.05). The findings indicated that sodium propionate encapsulated in molecularly imprinted polymer nanoparticles could enhance the efficiency of dietary SP in African cichlid fish.

Quantum confined peptide assemblies in a visual photoluminescent hydrogel platform and smartphone-assisted sample-to-answer analyzer for detecting trace pyrethroids

Quantum confinement (QC) effect-related materials have been extensively studied as photoluminescent probes for agricultural, food, and environmental analyses, with the advantage of simple-to-synthesize, reusable, nontoxic, and environmentally friendly. Herein, we propose a strategy to dimerize aromatic cyclo-dipeptides, namely cyclo-ditryptophan (cyclo-WW), cyclo-diphenylalanine (cyclo-FF), and cyclo-dihistidine (cyclo-HH), into quantum dots as basic building blocks for the self-assembly of QC supramolecular structures with excellent photoluminescent properties in aqueous solutions. In particular, through coordination with Zn(II), the bandgap can be tuned to change the photo-absorption and luminescence properties of the cyclo-dipeptide-based QC assemblies. The fluorescence quantum yield of cyclo-WW+Zn(II) was 16.9%. Such a good luminous effect makes it applicable to the detection of LC. A good linear relationship between fluorescence response of cyclo-WW+Zn(II) and LC concentration was observed in the range of 5-350 μg/L, with a low limit of detection of 2.9 μg/L and good spiked recovery of 90.72%-104.3%. A visual platform using the cyclo-WW+Zn(II)-based photoluminescent hydrogel and smartphone-assisted sample-to-answer analyzer were developed, which showed good responsiveness to LC. The developed fluorescence method, validated using traditional HPLC, is a biocompatible alternative for the rapid detection of trace pollutants with the advantages of portability and simple operation.

Development of enzyme/titanate nanosheet complex coated with molecularly imprinted polydopamine for colorimetric quercetin assay

A novel hybrid material, which is an enzyme/inorganic nanosheet complex coated by molecularly imprinted polymer (MIP), was developed, and applied to colorimetric quercetin assay. First, an enzyme/inorganic nanosheet complex was prepared from horseradish peroxidase (HRP) enzyme and titanate nanosheet (TiOx), using electrostatic interactions between them in acetate buffer. In the next place, dopamine self-polymerization was performed in the presence of HRP/TiOx complex with quercetin as a template, to prepare MIP membrane onto the HRP/TiOx complex. After washing process, a new hybrid material, MIP-coated HRP/TiOx complex (MIP-HT) was obtained. MIP-HT adsorbed quercetin efficiently, compared with NIP-HT that is an HRP/TiOx complex coated with non-imprinted polydopamine. MIP-HT showed enzymatic activity for an oxidation reaction of guaiacol, which is a chromogenic substrate of HRP, whereas the enzymatic activity of NIP-HT was significantly suppressed. The amount of brown product, formed by the color reaction, reduced owing to the presence of quercetin in sample solution, and a good liner relationship was observed between the concentration of quercetin and the increment of absorbance at 470 nm. The investigation using several biomolecules indicates that MIP-HT has the ability to detect quercetin and its analogues with selectivity. Therefore, MIP-HT shows great promise as a new and attractive material for use in colorimetric assay of quercetin or quercetin analogues.

Multivariate Assessment of Procedures for Molecularly Imprinted Polymer Synthesis for Pesticides Determination in Environmental and Agricultural Samples

In the case of quantitative and qualitative analysis of pesticides in environmental and food samples, it is required to perform a sample pre-treatment process. It allows to minimalize the impact of interferences on the final results, as well as increase the recovery rate. Nowadays, apart from routinely employed sample preparation techniques such as solid-phase extraction (SPE) or solid-phase microextraction (SPME), the application of molecularly imprinted polymers (MIPs) is gaining greater popularity. It is mainly related to their physicochemical properties, sorption capacity and selectivity, thermo-mechanical resistance, as well as a wide range of polymerization techniques allowing to obtain the desired type of sorption materials, adequate to a specific type of pesticide. This paper targets to summarize the most popular and innovative strategies since 2010, associated with the MIPs synthesis and analytical procedures for pesticides determination in environmental and food samples. Application of multi-criteria decision analysis (MCDA) allows for visualization of the most beneficial analytical procedures in case of changing the priority of each step of analysis (MIPs synthesis, sample preparation process—pesticides extraction, chromatographic analysis) bearing in mind metrological and environmental issues.

Ultrasensitive molecularly imprinted fluorescence sensor for simultaneous determination of CA125 and CA15-3 in human serum and OVCAR-3 and MCF-7 cells lines using Cd and Ni nanoclusters as new emitters

In the clinical diagnosis of tumors, a single-marker immunoassay may lead to false results. Thus there is a need for an effective and valid method for the simultaneous measurement of multiple tumor markers. In this work, an efficient fluorescence immunosensor for the simultaneous measurement of CA125 and CA15-3 tumor markers was fabricated by utilizing the high selectivity of magnetic molecularly imprinted polymers (MMIPs) and the high sensitivity of a fluorescence (FL) method. Ni nanoclusters (Ni NCs) and noble Cd nanoclusters (Cd NCs) were introduced as efficient and economic emitters, and magnetic graphene oxide (GO-Fe₃O₄) was applied as a support material for surface molecularly imprinted polymers. Under the most favorable experimental conditions, the fluorescence intensity of the Cd NCs and Ni NCs gradually increased with increasing concentration of CA125 and CA15-3 antigens at a range of 0.0005-40 U mL^-1, respectively, with a limit of detection (LOD) of 50 μU mL^-1. The developed method had excellent properties including a broad linear range, good reproducibility, and simple operation for the clinical diagnosis of CA 125 and CA 15-3 tumor markers. This molecularly imprinted fluorescence sensor has the potential to be an effective clinical tool for the timely screening of breast cancer in human serum samples and OVCAR-3 and MCF-7 cell lines, and can be applied in clinical diagnostics.

Affinity Sensing Strategies for the Detection of Pesticides in Food

This is a review of recent affinity-based approaches that detect pesticides in food. The importance of the quantification and monitoring of pesticides is firstly discussed, followed by a description of the different approaches reported in the literature. The different sensing approaches are reported according to the different recognition element used: antibodies, aptamers, or molecularly imprinted polymers. Schemes of detection and the main features of the assays are reported and commented upon. The large number of affinity sensors recently developed and tested on real samples demonstrate that this approach is ready to be validated to monitor the amount of pesticides used in food commodities.

Review of Sample Preparation Techniques for the Analysis of Selected Classes of Pesticides in Plant Matrices

The aim of this article is to present the trends in extraction techniques applied for the isolation of pesticides from plant matrix. To fully compare the effectiveness of different extraction techniques, it was required to analyze compounds with possibly wide spectrum of physicochemical properties. Hence, compounds representing neonicotinoids, pyrethroids, sulfonylureas and phenylamides were selected. Based on literature studies, it may be concluded that there are three main approaches to make the analytical procedures for pesticides determination more effective: (i) the optimization of extraction conditions, however, according to ANOVA conducted on the collected literature data, not all parameters influence the extraction process equally; chemometric studies based on literature reports may lead to the conclusion that the most favorable conditions (criterion: analyte recovery, repeatability) for neonicotinoid, pyrethroid and sulfonylurea herbicide extraction from plant tissues are provided by QuEChERS - extraction with acetonitrile, while the mixtures of PSA and GCB (for neonicotinoids), and PSA, GCB, C18 (for pyrethroids) should be used in d-SPE step. For sulfonylurea compounds and metalaxyl it was impossible to identify a sorbent(s) that cleans up the extract more effectively than the others; (ii) to develop a new generation of sorbents; however, the range of their applicability is limited, mainly due to difficulties in their synthesis; (iii) to develop the new extraction techniques with as few "trouble spots" as possible.

Synthesis of molecularly imprinted dye-silica nanocomposites with high selectivity and sensitivity: Fluorescent imprinted sensor for rapid and efficient detection of τ-fluvalinate in vodka

An imprinted fluorescent sensor was fabricated based on SiO₂ nanoparticles encapsulated with a molecularly imprinted polymer containing allyl fluorescein. High fluorine cypermethirin as template molecules, methyl methacrylate as functional monomer, and allyl fluorescein as optical materials synthesized a core-shell fluorescent molecular imprinted sensor, which showed a high and rapid sensitivity and selectivity for the detection of τ-fluvalinate. The sensor presented appreciable sensitivity with a limit of 13.251 nM, rapid detection that reached to equilibrium within 3 min, great linear relationship in the relevant concentration range from 0 to 150 nM, and excellent selectivity over structural analogues. In addition, the fluorescent sensor demonstrated desirable regeneration ability (eight cycling operations). The molecularly imprinted polymers ensured specificity, while the fluorescent dyes provided the stabile sensitivity. Finally, an effective application of the sensor was implemented by the detection of τ-fluvalinate in real samples from vodka. The molecularly imprinted fluorescent sensor showed a promising potential in environmental monitoring and food safety.

Molecularly Imprinted Polymer as an Antibody Substitution in Pseudo-immunoassays for Chemical Contaminants in Food and Environmental Samples

The chemical contaminants in food and the environment are quite harmful to food safety and human health. Rapid, accurate, and cheap detection can effectively control the potential risks derived from these chemical contaminants. Among all detection methods, the immunoassay based on the specific interaction of antibody-analyte is one of the most widely used techniques in the field. However, biological antibodies employed in the immunoassay usually cannot tolerate extreme conditions, resulting in an unstable state in both physical and chemical profiles. Molecularly imprinted polymers (MIPs) are a class of polymers with specific molecular recognition abilities, which are highly robust, showing excellent operational stability under a wide variety of conditions. Recently, MIPs have been used in biomimetic immunoassays for chemical contaminants as an antibody substitute in food and the environment. Here, we reviewed these applications of MIPs incorporated in different analytical platforms, such as enzyme-linked immunosorbent assay, fluorescent immunoassay, chemiluminescent immunoassay, electrochemical immunoassay, microfluidic paper-based immunoassay, and homogeneous immunoassay, and discussed current challenges and future trends in the use of MIPs in biomimetic immunoassays.

A novel fluorescent functional monomer as the recognition element in core–shell imprinted sensors responding to concentration of 2,4,6-trichlorophenol

We have demonstrated a fluorescent functional monomer instead of the traditional functional monomers for molecularly imprinted sensors. The sensors were firstly used to selectively detect 2,4,6-trichlorophenol (2,4,6-TCP) by solid fluorescence detection without a dispersion solution. Moreover, the selectivity and anti-interference ability of the SiO₂@dye-FMIPs sensor meet the requirements of a fluorescent sensor. The novel fluorescent monomer introduced into MIP is no longer just a fluorophore without recognizing ability. The fluorescence intensity of SiO₂@dye-FMIPs showed a linear response to 2,4,6-TCP concentration in the range of 0–100 nM with a detection limit of 0.0534 nM. We could also demonstrate that such a system can not only get rid of the confines of traditional functional monomers and detection manner, but also improved the applications of MIPs sensors in sensing systems.

We have demonstrated a molecularly imprinted sensor with a fluorescent functional monomer instead of the traditional functional monomers to detect 2,4,6-TCP.

Silica nanoparticle based techniques for extraction, detection, and degradation of pesticides

Silica nanoparticles (SiNPs) find applications in the fields of drug delivery, catalysis, immobilization and sensing. Their synthesis can be mediated in a facile manner and they display broad range compatibility and stability. Their existence in the form of spheres, wires and sheets renders them suitable for varied purposes. This review summarizes the use of silica nanostructures in developing techniques for extraction, detection and degradation of pesticides. Silica nanostructures on account of their sorbent properties, porous nature and increased surface area allow effective extraction of pesticides. They can be modified (with ionic liquids, silanes or amines), coated with molecularly imprinted polymers or magnetized to improve the extraction of pesticides. Moreover, they can be altered to increase their sensitivity and stability. In addition to the analysis of pesticides by sophisticated techniques such as High Performance Liquid Chromatography or Gas chromatography, silica nanoparticles related simple detection methods are also proving to be effective. Electrochemical and optical detection based on enzymes (acetylcholinesterase and organophosphate hydrolase) or antibodies have been developed. Pesticide sensors dependent on fluorescence, chemiluminescence or Surface Enhanced Raman Spectroscopic responses are also SiNP based. Moreover, degradative enzymes (organophosphate hydrolases, carboxyesterases and laccases) and bacterial cells that produce recombinant enzymes have been immobilized on SiNPs for mediating pesticide degradation. After immobilization, these systems show increased stability and improved degradation. SiNP are significant in developing systems for effective extraction, detection and degradation of pesticides. SiNPs on account of their chemically inert nature and amenability to surface modifications makes them popular tools for fabricating devices for 'on-site' applications.

Detection of λ-cyhalothrin by a core-shell spherical SiO2-based surface thin fluorescent molecularly imprinted polymer film

A fluorescent core-shell molecularly imprinted polymer based on the surface of SiO2 beads was synthesized and its application in the fluorescence detection of ultra-trace λ-cyhalothrin (LC) was investigated. The shell was prepared by copolymerization of acrylamide with allyl fluorescein in the presence of LC to form recognition sites. The experimental results showed that the thin fluorescent molecularly imprinted polymer (FMIP) film exhibited better selective recognition ability than fluorescent molecularly non-imprinted polymer (FNIP). A new nonlinear relationship between quenching rate and concentration was found in this work. In addition, the nonlinear relationship allowed a lower concentration range of 0-5.0 nM to be described by the Stern-Volmer equation with a correlation coefficient of 0.9929. The experiment results revealed that the SiO2@FMIP was satisfactory as a recognition element for determination of LC in soda water samples. Therefore this study demonstrated the potential of MIP for the recognition and detection of LC in food.

Synthesis of magnetic molecularly imprinted polymers by reversible addition fragmentation chain transfer strategy and its application in the Sudan dyes residue analysis

Magnetic molecularly imprinted polymers (MMIPs) have become a hotspot owing to the dual functions of target recognition and magnetic separation. In this study, the MMIPs were obtained by the surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization using Sudan I as the template. The resultant MMIPs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and X-ray diffraction. Benefiting from the controlled/living property of the RAFT strategy, the uniform MIP layer was successfully grafted on the surface of RAFT agent-modified Fe3O4@SiO2 nanoparticles, favoring the fast mass transfer and rapid binding kinetics. The developed MMIPs were used as the solid-phase extraction sorbents to selectively extract four Sudan dyes (Sudan I, II, III, and IV) from chili powder samples. The recoveries of the spiked samples in chili powder samples ranged from 74.1 to 93.3% with RSD lower than 6.4% and the relative standard uncertainty lower than 0.029. This work provided a good platform for the extraction and removal of Sudan dyes in complicated matrixes and demonstrated a bright future for the application of the well-constructed MMIPs in the field of solid-phase extraction.