Quantum dots coated with molecularly imprinted polymer as fluorescence probe for detection of cyphenothrin

ZnS:Mn Quantum Dots Coated with a Silica Molecularly Imprinted Polymer for Trace Teflubenzuron Detection in Vegetable Samples

A novel nanocomposite fluorescent probe consisting of quantum dots and a silica molecularly imprinted polymer (MIPs-capped ZnS:Mn QDs) was synthesized and applied for the rapid detection of teflubenzuron (TBZ) based on the fluorescence quenching of a composite probe via TBZ. The fluorescence quenching efficiency of MIP@SiO2@ZnS:Mn QDs displayed a linear relationship over the concentration range of 0-26.24 μmol/L with a correlation coefficient of 0.9857 and the limit of detection was 2.4 μg/L. The selectivity test showed that the nanocomposite had good selectively rebind TBZ with higher imprinting factor of 3.06 compared with four structurally similar compounds. In addition, the probe was successfully applied to the detection of TBZ in vegetable samples with a recovery of 90.3~97.1% and with a relative standard deviation below 3.2%. This developed method has the advantages of simple preparation, fast response and low toxicity for trace TBZ detection.

A highly efficient molecularly imprinted fluorescence sensor for assessing whole wheat grains by the rapid and sensitive detection of alkylresorcinols

To differentiate whole wheat foods from refined wheat foods is still challenging grain industry and confusing consumers. Alkylresorcinols (ARs), as biomarkers of whole wheat grains, can serve for assessing the authenticity of whole wheat foods. Herein, a highly efficient fluorescence sensing platform (CDs@MIP) for rapid and sensitive analysis of ARs was explored, using carbon dots (CDs) as fluorophores and 5-heneicosylresorcinol (C21:0 AR) as template molecules embedded in a molecularly imprinted polymer (MIP) coating. Benefiting from the specific cavities in the probe and a photo-induced electron transfer effect, the fluorescence intensity of CDs@MIP was significantly quenched in the presence of C21:0 AR, exhibiting a superior binding efficiency and selectivity. As a result, the fabricated optical sensor delivered a wide linear range of C21:0 AR from 0.015 to 60 μg mL-1 with an ultralow detection limit of 4 ng mL-1. It was noteworthy that the sensor was successfully applied for the rapid detection of C21:0 AR in commercial whole-wheat foods as well as visualization analysis on the test paper, comprehensively validating the practicality and efficacy of CDs@MIP based fluorescence assay. The study provides a rapid and sensitive detection method of C21:0 AR, paving a new way for guiding grain industry to effectively qualify the authenticity and to quantify the content of whole wheat in wheat-based foods.

Advances in Ultra-small Fluorescence Nanoprobes for Detection of Metal Ions, Drugs, Pesticides and Biomarkers

Identification of trace level chemical species (drugs, pesticides, metal ions and biomarkers) plays key role in environmental monitoring. Recently, fluorescence assay has shown significant advances in detecting of trace level drugs, pesticides, metal ions and biomarkers in real samples. Ultra-small nanostructure materials (metal nanoclusters (NCs), quantum dots (QDs) and carbon dots (CDs)) have been integrated with fluorescence spectrometer for sensitive and selective analysis of trace level target analytes in various samples including environmental and biological samples. This review summarizes the properties of metal NCs and ligand chemistry for the fabrication of metal NCs. We also briefly summarized the synthetic routes for the preparation of QDs and CDs. Advances of ultra-small fluorescent nanosensors (NCs, QDs and CDs) for sensing of metal ions, drugs, pesticides and biomarkers in various sample matrices are briefly discussed. Additionally, we discuss the recent challenges and future perspectives of ultra-small materials as fluorescent sensors for assaying of wide variety of target analytes in real samples.

Molecularly Imprinted Polymer-Coated Inorganic Nanoparticles: Fabrication and Biomedical Applications

Molecularly imprinted polymers (MIPs) continue to gain increasing attention as functional materials due to their unique characteristics such as higher stability, simple preparation, robustness, better binding capacity, and low cost. In particular, MIP-coated inorganic nanoparticles have emerged as a promising platform for various biomedical applications ranging from drug delivery to bioimaging. The integration of MIPs with inorganic nanomaterials such as silica (SiO₂), iron oxide (Fe₃O₄), gold (Au), silver (Ag), and quantum dots (QDs) combines several attributes from both components to yield highly multifunctional materials. These materials with a multicomponent hierarchical structure composed of an inorganic core and an imprinted polymer shell exhibit enhanced properties and new functionalities. This review aims to provide a general overview of key recent advances in the fabrication of MIPs-coated inorganic nanoparticles and highlight their biomedical applications, including drug delivery, biosensor, bioimaging, and bioseparation.

Analytical Chemistry: Tasks, Resolutions and Future Standpoints of the Quantitative Analyses of Environmental Complex Sample Matrices

Currently, the challenges that analytical chemistry has to face are ever greater and more complex both from the point of view of the selectivity of analytical methods and their sensitivity. This is especially true in quantitative analysis, where various methods must include the development and validation of new materials, strategies, and procedures to meet the growing need for rapid, sensitive, selective, and green methods. In this context, given the International Guidelines, which over time, are updated and which set up increasingly stringent “limits”, constant innovation is required both in the pre-treatment procedures and in the instrumental configurations to obtain reliable, accurate, and reproducible information. In addition, the environmental field certainly represents the greatest challenge, as analytes are often present at trace and ultra-trace levels. These samples containing analytes at ultra-low concentration levels, therefore, require very labor-intensive sample preparation procedures and involve the high consumption of organic solvents that may not be considered “green”. In the literature, in recent years, there has been a strong development of increasingly high-performing sample preparation techniques, often “solvent-free”, as well as the development of hyphenated instrumental configurations that allow for reaching previously unimaginable levels of sensitivity. This review aims to provide an update of the most recent developments currently in use in sample pre-treatment and instrument configurations in the environmental field, also evaluating the role and future developments of analytical chemistry in light of upcoming challenges and new goals yet to be achieved.

Toxicokinetic of cyphenothrin in rabbits

Type II pyrethroids, including cyphenothrin, have a wider efficacy and spectrum of action because they have a killing effect rather than a knockdown effect on pests. For this reason, they are among the most widely used pyrethroid groups today. In addition, this group also has repellent activity. Thus, cyphenothrin is a commonly used pyrethroid, which poses an exposure/toxicity risk for living organisms. Toxicokinetic studies have an important place in predicting the toxicity risks of compounds and evaluating viable treatment options. In this study, the toxicokinetics of cyphenothrin were investigated in rabbits. The animal material of the study comprised 6-month-old female 14 New Zealand rabbits, each weighing 2-2.5 kg. The animals were randomly assigned to two groups, each of 7 animals. The rabbits in group 1 were administered a single dose of 2.5 mg/kg bw cyphenothrin in dimethyl sulfoxide as an intravenous bolus, while the rabbits in group 2 were administered a single dose of 2.5 mg/kg bw cyphenothrin in the same vehicle as an oral bolus. Following the administration of cyphenothrin, blood samples were taken at certain intervals from the auricular vein into heparinized tubes. Plasma cyphenothrin levels were determined by gas chromatography, using a capillary column and a micro-electron capture detector. For orally administered cyphenothrin, the plasma maximum concentration (Cmax), time to reach the maximum value (tmax), half-life (t1/2β), mean residence time (MRT), area under the curve (AUC0→∞), and bioavailability (F) values were determined as 172.28 ± 47.30 ng/ml, 1.07 ± 0.42 h, 12.95 ± 1.11 h, 17.79 ± 1.69 h, 2220.07 ± 572.02 ng/h/ml, and 29.50%, respectively. For intravenous cyphenothrin, the t1/2β, MRT and AUC0→∞ values were ascertained as 7.66 ± 0.74 h, 9.28 ± 0.62 h, and 7524.31 ± 2988.44 ng/h/ml, respectively. Although the bioavailability of cyphenothrin was limited when taken orally, its half-life and mean residence time in the body were found to be long. This suggests that high doses of this pesticide may pose a poisoning risk.

Mycotoxins detection: view in the lens of molecularly imprinted polymer and nanoparticles

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed.

Molecularly Imprinted Polymers (MIPs) in Sensors for Environmental and Biomedical Applications: A Review

Molecular imprinted polymers are custom made materials with specific recognition sites for a target molecule. Their specificity and the variety of materials and physical shapes in which they can be fabricated make them ideal components for sensing platforms. Despite their excellent properties, MIP-based sensors have rarely left the academic laboratory environment. This work presents a comprehensive review of recent reports in the environmental and biomedical fields, with a focus on electrochemical and optical signaling mechanisms. The discussion aims to identify knowledge gaps that hinder the translation of MIP-based technology from research laboratories to commercialization.

Recent Advances on Detection of Insecticides Using Optical Sensors

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides.

A magnetic phosphorescence molecularly imprinted polymers probe based on manganese-doped ZnS quantum dots for rapid detection of trace norfloxacin residual in food

This paper reports the development of a novel probe based on magnetic room-temperature phosphorescence quantum dots with molecularly imprinted polymers (MQD-MIPs) for the rapid detection of trace norfloxacin (NFX) residual in complex food matrix. The highly selective probe was constructed by surface molecular imprinting technology using magnetic materials (Fe₃O₄ nanoparticles) as core, Mn-doped ZnS quantum dots (Mn-ZnS QDs) as phosphorescent materials, NFX as template, 3-aminopropyltriethoxysilane as functional monomer, and tetraethoxysilane as crosslinking agent. The as-obtained MQD-MIPs were characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometry, and vibrating sample magnetometer. A magnetic strength of 37.64 emu g^-1 was recorded. Also, the probe displayed excellent room temperature phosphorescence properties with excitation/emission peaks at 300/590 nm. Under the optimized conditions, the detection time was less than 40 min, phosphorescence intensity varied linearly with concentration from 1 to 90 μg·L^-1, and detection limit reached as low as 0.80 μg·L^-1. Furthermore, the MQD-MIPs-based probe successfully detected norfloxacin residues in spiked fish and milk samples with recoveries of 90.92-111.53% and RSD <7%, outperforming the standard control method-HPLC-FLD (recoveries of 85.89-118.28%).

Molecularly Imprinted Polymer-Quantum Dot Materials in Optical Sensors: An Overview of Their Synthesis and Applications

In the last decades analytical methods have focused on the determination of target analytes at very low concentration levels. This has been accomplished through the use of traditional analytical methods that usually require high reagent consumption, expensive equipment and long pretreatment steps. Thus, there is a demand for simple, rapid, highly selective and user-friendly detection procedures. Quantum dots (QDs) are semiconductor fluorescent nanomaterials with unique optoelectronic properties that have shown great potential for the development of fluorescence probes. Besides, the combination of QDs with molecularly imprinted polymer (MIPs), synthetic materials with selective recognition, have been proposed as useful materials in the development of optical sensors. The resulting MIP-QDs optical sensors integrate the advantages of both techniques: the high sensitivity of QDs-based fluorescence sensors and the high selectivity of MIPs. This review gives a brief overview of the strategies for the synthesis of MIPs-QDs based optical sensors, highlighting the modifications in the synthesis procedure that improve the sensor performance. Finally, a revision of recent applications in sensing and bioimaging is presented.

pH-Response Quantum Dots with Orange-Red Emission for Monitoring the Residue, Distribution, and Variation of an Organophosphorus Pesticide in an Agricultural Crop

Development of simple, sensitive, and reliable fluorescence sensors for monitoring the residue, distribution, and variation of organophosphorus pesticides (OPs) in agricultural crops is highly urgent but remains challenging, which is ascribed to deprivation of an ideal fluorophore and ingenious detection strategy. Herein, we report the fabrication of cadmium telluride quantum dots (CdTe QDs) with bright emission, good water dispersion, and long emission wavelength for OP screening based on the unique response of CdTe QDs to pH and the inhibition of OPs on acetylcholinesterase (AChE) activity. AChE catalyzed hydrolysis of acetylcholine (ACh) into CH₃COOH, which protonated CdTe QDs to decline the fluorescence, whereas target OP impeded AChE from catalyzing hydrolysis of ACh into CH₃COOH, making little influence in fluorescence of CdTe QDs. On the basis of the change in fluorescence, sensitive detection of OP was acquired, with the limit of detection at 0.027 ng/mL, which was comparable or lower than that of most known OP sensors. Furthermore, the CdTe-QD-based sensor was successfully applied for precisely monitoring the residue, distribution, and variation of methidathion in Chinese cabbage and cultivated soil. Therefore, the proposed sensor was anticipated to supply a promising alternative for food safety guarantee and was an valuable application for OP screening.

Enhanced selectivity and sensitivity for colorimetric determination of glyphosate using Mn-ZnS quantum dot embedded molecularly imprinted polymers combined with a 3D-microfluidic paper-based analytical device

We report a novel three-dimensional microfluidic paper-based analytical device (3D-μPAD) with colorimetric detection, using Mn-ZnS quantum dot embedded molecularly imprinted polymer (Mn-ZnS QD-MIP), for selective glyphosate determination in whole grain samples. Detection is based on the catalytic activity of Mn-ZnS QD-MIP in the H₂O₂ oxidation of ABTS. Glyphosate imprinted polymer is successfully synthesized on the Mn-ZnS QD surface using a poly (N-isopropylacrylamide) (NIPAM) and N, N'-Methylenebisacrylamide (MBA) as the functional monomers. The catalytic activity depends on binding or non-binding of glyphosate molecules on the synthetic recognition sites of the Mn-ZnS QD-MIP. Glyphosate selectively binds to the cavities embedded on the Mn-ZnS QD surface, and subsequently turns-off or inhibits the ABTS oxidation and color change to light green. The change of reaction color from dark green to light green depends on the concentration of glyphosate. We report, for the first time, using the relatively new penguard enamel colour to create a hydrophobic barrier. The foldable 3D-μPAD comprises three layers (top/center/bottom), named as the detection zone, immobilized Mn-ZnS QD-MIP disc, and sample loading. Assay on the 3D-μPAD can determine glyphosate by ImageJ detection, over an operating range of 0.005-50 μg mL^-1 and with a detection limit of 0.002 μg mL^-1. Our 3D-μPAD exhibits high accuracy, with a 0.4% (intra-day) and 0.7% (inter-day) relative difference from the certified CRM value. Moreover, the fabricated 3D-μPAD provides good reproducibility (1.7% RSD for ten devices). The developed 3D-μPAD was successfully applied to determine the glyphosate concentration in whole grain samples and shows great promise as an alternative highly selective and sensitive colorimetric method. The 3D-μPAD is well suited to food-quality control and onsite environmental-monitoring applications, without sophisticated instrumentation.

The Recent Advances of Fluorescent Sensors Based on Molecularly Imprinted Fluorescent Nanoparticles for Pharmaceutical Analysis

Fluorescent nanoparticles have good chemical stability and photostability, controllable optical properties and larger stokes shift. In light of their designability and functionability, the fluorescent nanoparticles are widely used as the fluorescent probes for diverse applications. To enhance the sensitivity and selectivity, the combination of the fluorescent nanoparticles with the molecularly imprinted polymer, i.e. molecularly imprinted fluorescent nanoparticles (MIFN), was an effective way. The sensor based on MIFN (the MIFN sensor) could be more compatible with the complex sample matrix, which was especially widely adopted in medical and biological analysis. In this mini-review, the construction method, detective mechanism and types of MIFN sensors are elaborated. The current applications of MIFN sensors in pharmaceutical analysis, including pesticides/herbicide, veterinary drugs/drugs residues and human related proteins, are highlighted based on the literature in the recent three years. Finally, the research prospect and development trend of the MIFN sensor are forecasted.

Fluorescent nanomaterials combined with molecular imprinting polymer: synthesis, analytical applications, and challenges

Fluorescent nanomaterials (FNMs) and molecular imprinted polymers (MIPs) have been widely used in analytical chemistry for determination. However, low selectivity of FNMs and low sensitivity of MIPs hinder their applications. Combining the merits of FNMs and MIPs, FNMs coated with MIPs (FNMs@MIPs) were proposed to solve those problems. Carbon dots, semiconductor quantum dots, noble metal nanoparticles, silica nanoparticles, and covalent-organic frameworks have been reported to be coated with MIPs. In order to overcome challenges for FNMs@MIPs, such as the lack of handy synthesis routes, incompatibility with aqueous solutions, heterogeneous size of particles, leakage of template molecules, the biocompatibility of FNMs@MIPs, and the inference between FNMs and MIPs, scientists proposed some solutions in recent years. We comprehensively review the newest advances of the FNMs@MIPs, and predict the direction of the future development. Graphical abstract.

A fluorescence microplate assay based on molecularly imprinted silica coated quantum dot optosensing materials for the separation and detection of okadaic acid in shellfish

Molecularly imprinted polymers (MIPs) are attracting substantial interest as artificial plastic antibodies because of their biometric capability for targeting small molecules. In this study, molecularly imprinted silica material-coated quantum dots (MIS-QDs) with selective recognition capability to okadaic acid (OA) were developed and characterized. The synthesized MIS-QDs with specific imprinting cavities exhibited excellent recognition capability similar to those of biological antibodies and high fluorescence (FL) quenching selectivity for OA. Furthermore, the MIS-QDs with unsaturated bonds were immobilized onto the surface of 96-well microplates by cold plasma-induced grafting. A novel direct competitive microplate assay strategy was then proposed. The FL quenching properties of the developed microplate assay showed an excellent linear relationship with OA in the range of 10.0-100.0 μg/kg with a correlation coefficient of 0.9961. The limit of detection for OA was 0.25 μg/kg in the shellfish samples. The mean quantitative recoveries were 92.5%-101.0% and 92.9%-101.3%, with relative standard deviations of <7.7% and 7.6% for pure solvents and purified shellfish samples, respectively. The established microplate assay strategy can be used as a rapid and high-throughput method for analyzing OA marine toxins in biological samples.

Molecularly imprinted polymer containing fluorescent graphene quantum dots as a new fluorescent nanosensor for detection of methamphetamine

A novel fluorescent nanosensor based on graphene quantum dots embedded within molecularly imprinted polymer (GQDs@MIP) was developed for detection and determination of methamphetamine (METH). The resulting GQDs@MIP nanocomposite exhibited higher methamphetamine selectivity in comparison with corresponding non-imprinted polymer (GQDs@NIP). Characterization of the GQDs@MIP nanocomposite was done by nitrogen adsorption and desorption analysis (BET method), transmission electron microscopy (TEM), photoluminescence (PL), ultraviolet-visible (UV-Vis), and Fourier transform infrared (FT-IR) spectroscopies. The fluorescence intensity of GQDs@MIP was efficiently quenched in the presence of methamphetamine template molecules while no quenching was observed in the presence of other analytes such as amphetamine, ibuprofen, codeine, and morphine. Using this method, the detection limit of 1.7 μg/L was obtained for methamphetamine determination.

Highly Selective Electrochemiluminescence Sensor Based on Molecularly Imprinted-quantum Dots for the Sensitive Detection of Cyfluthrin

A highly selective and sensitive molecularly imprinted electrochemiluminescence (MIECL) sensor was developed based on the multiwall carbon nanotube (MWCNT)-enhanced molecularly imprinted quantum dots (MIP-QDs) for the rapid determination of cyfluthrin (CYF). The MIP-QDs fabricated by surface grafting technique exhibited excellent selective recognition to CYF, resulting in a specific decrease of ECL signal at the MWCNT/MIP-QD modified electrode. Under optimal conditions, the MIECL signal was proportional to the logarithm of the CYF concentration in the range of 0.2 µg/L to 1.0 × 10³ µg/L with a determination coefficient of 0.9983. The detection limit of CYF was 0.05 µg/L, and good recoveries ranging from 86.0% to 98.6% were obtained in practical samples. The proposed MIECL sensor provides a novel, rapid, high sensitivity detection strategy for successfully analyzing CYF in fish and seawater samples.

Fabrication of carbon dots@restricted access molecularly imprinted polymers for selective detection of metronidazole in serum

A custom-tailored design was proposed for the fabrication of carbon dots coupled with restricted access materials and molecularly imprinted polymers (CDs@RAM-MIPs) to detect metronidazole (MNZ). Biomass carbon dots (CDs) were derived from longan peels assisted with high pressure microwave, and had the merits of eco-friendly, excellent photostability and low toxicity. In this work, glycidyl methacrylate was used as a co-polymeric monomer to increase hydroxyl groups on the surface of synthetic materials, which eliminated the interference of biological macromolecules. The specific binding cavities of CDs@RAM-MIPs were formed after removing the template molecule (MNZ). The obtained CDs@RAM-MIPs can selectively capture MNZ through the specific interaction between recognition sites and MNZ, and obey photoinduced electron transfer fluorescence quenching mechanism. The highly sensitive and selective fluorescent sensor based CDs@RAM-MIPs had a wide linear range (50-1200 ng mL^-1) and a low detection limit (17.4 ng mL^-1) for MNZ. It has been utilized to detect MNZ in serum with recoveries of 93.5%-102.7%, and the relative standards (RSDs) were 1.9%-3.6%, respectively. This work provides a thoughtful strategy for preparation and application of CDs@RAM-MIPs, which presages its great potential for detecting trace compounds in real samples.

Molecularly Imprinted Polyacrylamide with Fluorescent Nanodiamond for Creatinine Detection

Creatinine measurement in blood and urine is an important diagnostic test for assessing kidney health. In this study, a molecularly imprinted polymer was obtained by incorporating fluorescent nanodiamond into a creatinine-imprinted polyacrylamide hydrogel. The quenching of peak nanodiamond fluorescence was significantly higher in the creatinine-imprinted polymer compared to the non-imprinted polymer, indicative of higher creatinine affinity in the imprinted polymer. Fourier transform infrared spectroscopy and microscopic imaging was used to investigate the nature of chemical bonding and distribution of nanodiamonds inside the hydrogel network. Nanodiamonds bind strongly to the hydrogel network, but as aggregates with average particle diameter of 3.4 ± 1.8 µm and 3.1 ± 1.9 µm for the non-imprinted and molecularly imprinted polymer, respectively. Nanodiamond fluorescence from nitrogen-vacancy color centers (NV^- and NV⁰) was also used to detect creatinine based on nanodiamond-creatinine surface charge interaction. Results show a 15% decrease of NV^-/NV⁰ emission ratio for the creatinine-imprinted polymer compared to the non-imprinted polymer, and are explained in terms of changes in the near-surface band structure of diamond with addition of creatinine. With further improvement of sensor design to better disperse nanodiamond within the hydrogel, fluorescent sensing from nitrogen-vacancy centers is expected to yield higher sensitivity with a longer range (Coulombic) interaction to imprinted sites than that for a sensor based on acceptor/donor resonance energy transfer.

Recent advances of molecularly imprinted polymer-based sensors in the detection of food safety hazard factors

With increasing economic globalization, food safety is becoming the most serious concern in the food production and distribution system. Food safety hazard factors (FSHFs) can be categorized into chemical hazards, biological hazards and physical hazards, with the detection of the former two having fascinated interdisciplinary research areas spanning chemistry, material science and biological science. Molecularly imprinted polymer (MIP) -based sensors overcome many limitations of traditional detection methods and provide opportunities for efficient, sensitive and low-cost detection using smart miniaturized equipment. With highly specific molecular recognition capacity and high stability in harsh chemical and physical conditions, MIPs have been used in sensing platforms such as electrochemical, optical and mass-sensitive sensors as promising alternatives to bio-receptors for food analysis. In this systemic review, we summarize recent advances of MIPs and MIP-based sensors, such as popular monomers, usual polymerization strategies, fresh modification materials and advanced sensing mechanisms. The applications of MIP-based sensors in FSHF detection are discussed according to sensing mechanisms, including electrochemistry, optics and mass-sensitivity. Finally, future perspectives and challenges are discussed.

Synthesis of molecularly imprinted fluorescent probe based on biomass-derived carbon quantum dots for detection of mesotrione

A novel fluorescent probe based on molecularly imprinted polymers (MIPs) coupled with carbon quantum dots (CQDs) was fabricated and successfully used for selective recognition of mesotrione. In this probe, the biomass-derived CQDs were prepared through a hydrothermal method using mango peels as carbon source, and the whole synthesis procedure was green without chemical reagents. The CQDs were encapsulated into MIPs by using sol-gel technology. After removal of the template molecule mesotrione, specific binding sites are formed and there is electrostatic attraction between the probe and the template molecule. The synthetic CQDs@MIPs were able to selectively capture the target mesotrione with fluorescence quenching via the specific interaction between mesotrione and the recognition cavities. The probe was used for determination of mesotrione in corn to verify the practicality of the proposed method. The detection limit of mesotrione was 4.7 nmol L^-1, and the linear range was 15 nmol L^-1 to 3000 nmol L^-1. Meanwhile, the recoveries of this method for mesotrione were 91.4-96.2%, and the relative standard deviations (RSDs) were 3.2-6.1%. This work provides a novel research method to synthesize CQDs@MIPs with high selectivity (imprinting factor = 5.6), and which can be used for convenient, rapid recognition and sensitive detection of trace compounds from complex matrices.

Rapid detection of aflatoxin B1 by dummy template molecularly imprinted polymer capped CdTe quantum dots

A novel and sensitive fluorescent sensor was synthesized for the rapid and specific recognition of aflatoxin B₁ (AFB1) by our combining molecular imprinting techniques with quantum dot technology. Molecularly imprinted polymers coated CdTe quantum dots (MIP@CdTe QDs) were prepared through the Stöber method with 5,7-dimethoxycoumarin as a dummy template. 3-Aminopropyltriethoxysilane was selected as the functional monomer, and tetraethyl orthosilicate was used as the cross-linking agent. The best molar ratio of 5,7-dimethoxycoumarin to functional monomer to cross-linker was 4:20:15. The MIP@CdTe QD composites were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence spectroscopy. Under the optimum conditions, the relative fluorescence intensity of the MIP@CdTe QDs showed adequate linearity with AFB1 concentration over the range from 80 to 400 ng/g. The detection limit is 4 ng/g, according to 3s/K. Finally, the method was successfully applied to the quantitative determination of AFB1 in real samples. The spike recoveries at different spiking levels ranged from 99.20% to 101.78%, which were consistent with those measured by ultrahigh-performance liquid chromatography-mass spectrometry. The method developed for AFB1 detection lays the foundation for rapid detection of trace amounts of other exogenous harmful substances in a complicated matrix.

A luminescence nanosensor for Ornidazole detection using graphene quantum dots entrapped in silica molecular imprinted polymer

A luminescence nanosensor has been developed for analysis of Ornidazole in biological samples using graphene-quantum-dot-embedded silica molecular imprinted polymer (GQD-SMIP) as a selective probe for this analyte. The GQD-SMIP was found to possess a strong fluorescent emission at 450 nm upon excitation at 365 nm. This emission was found to linearly quench in the presence of Ornidazole in a concentration range of 0.75 to 30 μM. A detection limit of 0.24 μM was reached using the probe and the sensor was successfully used in the determination of the analyte in plasma samples.

Novel Fluorescence Sensor Based on All-Inorganic Perovskite Quantum Dots Coated with Molecularly Imprinted Polymers for Highly Selective and Sensitive Detection of Omethoate

All-inorganic cesium lead halide perovskites (CsPbX₃, X = Cl, Br, and I) have attracted considerable attention with superior electrical and photophysical properties. In this study, luminescent perovskite (CsPbBr₃) quantum dots (QDs) as sensing elements combined with molecularly imprinted polymers (MIPs) are used for the detection of omethoate (OMT). The new MIPs@CsPbBr₃ QDs were synthesized successfully through the imprinting technology with a sol-gel reaction. The fluorescence (FL) of the MIPs@CsPbBr₃ QDs was quenched obviously on loading the MIPs with OMT, the linear range of OMT was from 50 to 400 ng/mL, and the detection limit was 18.8 ng/mL. The imprinting factor was 3.2, which indicated excellent specificity of the MIPs for the inorganic metal halide (IMH) perovskites. The novel composite possesses the outstanding FL capability of CsPbBr₃ QDs and the high selectivity of molecular imprinting technology, which can convert the specific interactions between template and the imprinted cavities to apparent changes in the FL intensity. Hence, a selective and simple FL sensor for direct and fast detection of organophosphorus pesticide in vegetable and soil samples was developed here. The present work also illustrates the potential of IMH perovskites for sensor applications in biological and environmental detection.

Fluorometric determination of quercetin by using graphitic carbon nitride nanoparticles modified with a molecularly imprinted polymer

The authors describe a fluorescent probe for sensitive and selective determination of quercetin, an indicator for the freshness of drinks. The probe consists of silica ball encapsulated graphitic carbon nitride (g-C₃N₄) modified with a molecularly imprinted polymer (MIP). It was synthesized via reverse microemulsion. The resulting MIP@g-C₃N₄ nanocomposite was characterized by fluorescence spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray powder diffraction. Quercetin quenches the fluorescence of the MIP@g-C₃N₄ probe. The effect was used to quantify quercetin in grape juice, tea juice, black tea, and red wine by fluorometry (λ_exc = 350 nm, λ_em = 460 nm). Response is linear in the 10-1000 ng mL^-1 quercetin concentration range. The detection limit is 2.5 ng mL^-1, recoveries range between 90.7 and 94.1%, and relative standard deviations are between 2.1 and 5.5%. Graphical abstract Schematic of the synthesis of the MIP@g-C₃N₄ by a reverse microemulsion method. The probe was applied for the selective recognition and fluorometric determination of quercetin.