Preparation of dummy molecularly imprinted polymers based on dextran-modified magnetic nanoparticles Fe3O4 for the selective detection of acrylamide in potato chips

Sensing technology empowering food safety: research progress of SERS-assisted multimodal biosensing toward food hazard factors

Food is the main source of human energy and nutrition, but once it is contaminated with hazardous factors, such as biotoxins, pesticide residues, etc., it will seriously damage health. This paper reviews the research progress of biosensors based on surface-enhanced Raman scattering (SERS) in the detection of food hazard factors. First, the basic principle, substrate and assay mode of SERS technology, as well as related design and sensing strategy mechanisms, are introduced. Then, the design idea of multimodal biosensors combining SERS with microfluidic, fluorescence, colorimetric, electrochemical (EC), molecular imprinting and other technologies is expounded to improve the analysis accuracy and specificity. Then the application results of multimodal biosensors based on SERS sensing toward food hazard factors are discussed, and the necessity of its development is illustrated. Finally, the future development direction of this field is prospected, which provides a reference for promoting the research and application of multimodal biosensors based on SERS.

Research Progress on the Enhancement of Immobilized Enzyme Catalytic Performance and Its Application in the Synthesis of Vitamin E Succinate

Vitamin E succinate is a more mature vitamin E derivative, and its chemical stability and many effects have been improved compared with vitamin E, which can not only make up for the shortcomings of vitamin E application but also broaden the application field of vitamin E. At present, in developed countries such as Europe, America, and Japan, vitamin E succinate is widely used in health foods, and due to its good water solubility and stability, the vitamin E added to most nutritional supplements (tablets and hard capsules) is vitamin E succinate. At the same time, vitamin E succinate used in the food and pharmaceutical industries is mainly catalyzed by enzymatic catalysis. In this paper, Candida rugosa lipase (CRL) was studied. Chemical modification and immobilization were used to improve the enzymatic properties of CRL, and immobilized lipase with high stability and high activity was obtained. It was applied to the enzymatic synthesis of vitamin E succinate, and the reaction conditions were optimized to improve the yield and reduce the production cost. The review covered the research progress of the methods for enhancing the catalytic performance of immobilized enzymes and discussed its application in the synthesis of vitamin E succinate, providing new ideas and technical support for the catalytic performance enhancement of immobilized enzymes and its application in the synthesis of vitamin E succinate and promoting the production and application of vitamin E succinate.

Application Progress of Immobilized Enzymes in the Catalytic Synthesis of 1,3-Dioleoyl-2-palmitoyltriglyceride Structured Lipids

In recent years, the preparation of OPO (1,3-dioleoyl-2-palmitoyltriglyceride)-structured lipids through immobilized lipase catalysis has emerged as a research hotspot in the fields of food and biomedical sciences. OPO structured lipids, renowned for their unique molecular structure and biological functions, find wide applications in infant formula milk powder, functional foods, and nutritional supplements. Lipase-catalyzed reactions, known for their efficiency, high selectivity, and mild conditions, are ideal for the synthesis of OPO structured lipids. Immobilized lipases not only address the issues of poor stability and difficult recovery of free enzymes but also enhance catalytic efficiency and reaction controllability. This review summarizes the latest advancements in the synthesis of OPO structured lipids using immobilized lipases, focusing on immobilization methods, enhancements in enzyme activity and stability, the optimization of reaction conditions, and improvements in product purity and yield. Furthermore, it delves into the reaction mechanisms of enzymatic synthesis of OPO structured lipids, process optimization strategies, and the challenges and broad prospects faced during industrial applications.

Synthesis, modifications, and applications of iron-based nanoparticles

Magnetic nanoparticles (MNPs) are appealing materials as assistant to resolve environmental pollution issues and as recyclable catalysts for the oxidative degradation of resistant contaminants. Moreover, they can significantly influence the advancement of medical applications for imaging, diagnostics, medication administration, and biosensing. On the other hand, due to unique features, excellent biocompatibility, high curie temperatures and low cytotoxicity of the Iron-based nanoparticles, they have received increasing attention in recent years. Using an external magnetic field, in which the ferrite magnetic nanoparticles (FMNPs) in the reaction mixtures can be easily removed, make them more efficient approach than the conventional method for separating the catalyst particles by centrifugation or filtration. Ferrite magnetic nanoparticles (FMNPs) provide various advantages in food processing, environmental issues, pharmaceutical industry, sample preparation, wastewater management, water purification, illness therapy, identification of disease, tissue engineering, and biosensor creation for healthcare monitoring. Modification of FMNPs with the proper functional groups and surface modification techniques play a significant role in boosting their capability. Due to flexibility of FMNPs in functionalization and synthesis, it is possible to make customized FMNPs that can be utilized in variety of applications. This review focuses on synthesis, modifications, and applications of Iron-based nanoparticles.

Dual-template magnetic molecularly imprinted polymers for selective extraction and sensitive detection of aflatoxin B1 and benzo(α)pyrene in environmental water and edible oil

The coexistence of multiple contaminates in the environment and food is of growing concern due to their extremely hazard as a well-known class I carcinogen, like aflatoxin B1 (AFB1) and benzo(α)pyrene (BaP). AFB1 and BaP are susceptible to coexistence in environmental water and edible oil, posing a significant potential risk to environmental monitoring and food safety. The remaining challenges in detecting multiple contaminates include unsatisfied sensitivity, insufficient targets selectivity, and interferences in complex matrices. Here, we developed dual-template magnetic molecularly imprinted polymers (DMMIPs) for selective extraction of dual targets in complex matrices from the environment and food. The DMMIPs were fabricated by surface imprinting with vinyl-functionalized Fe3O4 as carrier, 5,7-dimethoxycoumarin and pyrene as dummy templates, and methacrylamide as functional monomer. The DMMIPs showed excellent adsorption ability (12.73-15.80 mg/g), imprinting factors (2.01-2.58), and reusability of three adsorption-desorption cycles for AFB1 and BaP. The adsorption mechanism including hydrogen bond, electrostatic interaction and van der Waals force was confirmed by physical characterization and DFT calculation. Applying DMMIPs in magnetic solid phase extraction (MSPE) followed by high-performance liquid chromatography (HPLC) analysis enabled detection limits of 0.134 μg/L for AFB1 and 0.107 μg/L for BaP. Recovery rates for water and edible oil samples were recorded as 86.2%-110.3% with RSDs of 4.1%-11.9%. This approach demonstrates potential for simultaneous identification and extraction of multiple contaminants in environmental and food.

Assessment of Acrylamide Levels by Advanced Molecularly Imprinted Polymer-Imprinted Surface Plasmon Resonance (SPR) Sensor Technology and Sensory Quality in Homemade Fried Potatoes

This study evaluated acrylamide (AA) levels and various quality parameters in homemade fried potatoes prepared in different sizes by integrating principles from the Slow Food Movement with advanced sensor technology. To this aim, a surface plasmon resonance (SPR) sensor based on a molecularly imprinted polymer (MIP) was first developed for the determination of AA in homemade fried potatoes at low levels, and the AA levels in the samples were established. First of all, monolayer formation of allyl mercaptane on the SPR chip surface was carried out to form double bonds that could polymerize on the chip surface. AA-imprinted SPR chip surfaces modified with allyl mercaptane were prepared via UV polymerization using ethylene glycol dimethacrylate (EGDMA) as a cross-linker, N,N'-azobisisobutyronitrile (AIBN) as an initiator, and methacryloylamidoglutamicacid (MAGA) as a monomer. The prepared AA-imprinted and nonimprinted surfaces were characterized by atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy methods. The SPR sensor indicated linearity in the range of 1.0 × 10-9-5.0 × 10-8 M with a detection limit (LOD) of 3.0 × 10-10 M in homemade fried potatoes, and the SPR sensor demonstrated high selectivity and repeatability in terms of AA detection. Additionally, the highest AA level was observed in the potato sample belonging to the T1 group, at 15.37 nM (p < 0.05), and a strong and positive correlation was found between AA levels and sensory parameters, the a* value, the ΔE value, and the browning index (BI) (p < 0.05).

Mobile phone-assisted imprinted nanozyme for bicolor colorimetric visual detection of erythromycin in river water and milk samples

The residues of erythromycin (ERY) may have negative impacts on the ecological environment, health, and food safety. How to detect ERY effectively and visually is a challenging issue. Herein, we synthesized a molecularly imprinted polymer based nanozymes for selective detection of erythromycin (ERY-MIPNs) at neutral pH, and developed a mobile phone-assisted bicolor colorimetric detection system. This system produced a wide range of color changes from blue to pinkish purple as the ERY concentration increased, making it easy to capture the visualization result. Also, the system showed good sensitivity to ERY ranging from 15 to 135 μM, with a detection limit of 1.78 μM. In addition, the system worked well in the detection of ERY in river water and milk, with the recoveries of 95.57% ∼ 103.20%. These data suggests that this strategy is of considerable potential for practical applications and it provides a new idea for visual detection with portable measurement.

Recent advances in molecularly imprinted polymers (MIPs) for visual recognition and inhibition of α-dicarbonyl compound-mediated Maillard reaction products

α-Dicarbonyl compounds (α-DCs) are important intermediates and precursors of harmful Maillard reaction products (e.g., acrylamide and late glycosylation end-products), and they exist widely in thermoprocessed sugar- or fat-rich foods. α-DCs and their end-products are prone to accumulation in the human body and lead to the development of various chronic diseases. Therefore, detection of α-DCs and their associated hazards in food samples is crucial. This paper reviews the preparation of molecularly imprinted polymers (MIPs) enabling visual intelligent responses and the strategies for recognition and capture of α-DCs and their associated hazards, and provides a comprehensive summary of the development of visual MIPs, including integration strategies and applications with real food samples. The visual signal responses as well as the mechanisms for hazard recognition and capture are highlighted. Current challenges and prospects for visual MIPs with advanced applications in food, agricultural and environmental samples are also discussed. This review will open new horizons regarding visual MIPs for recognition and inhibition of hazards in food safety.

Current trends of functional monomers and cross linkers used to produce molecularly imprinted polymers for food analysis

Molecularly imprinted polymers (MIPs) as artificial synthetic receptors are in high demand for food analysis due to their inherent molecular recognition abilities. It is common practice to employ functional monomers with basic or acidic groups that can interact with analyte molecules via hydrogen bonds, covalent bonds, and other interactions (π-π, dipole-ion, hydrophobic, and Van der Waals). Therefore, selecting the appropriate functional monomer and cross-linker is crucial for determining how precisely they interact with the template and developing the polymeric network's three-dimensional structure. This study summarizes the advancements made in MIP's functional monomers and cross-linkers for food analysis from 2018 to 2023. The subsequent computational design of MIP has been thoroughly explained. The discussion has concluded with a look at the difficulties and prospects for MIP in food analysis.

Oriented assembly of hydrophilic nanochains modified by porous zirconium-based coordination polymers for glycopeptides analysis

Mass spectrometry (MS)-based glycoproteomics research requires additional sample pretreatment to improve the effective identification of low-abundance glycopeptides without interference from non-glycoproteins. Herein, an attractive strategy using resorcinol-formaldehyde (RF) resin and zirconium-based coordination polymer (Zr-BCP) was established to prepare one-dimensional porous coordination polymer composites for glycopeptide enrichment before MS analysis. The obtained Fe3O4@RF@Zr-BCP nanochains feature excellent magnetic response (42.26 emu/g), high hydrophilicity (16.0°), and large specific surface area (140.84 m2/g), which provides abundant affinity sites for specific capture of glycopeptides. The materials exhibit outstanding performance in the enrichment of glycopeptides in terms of sensitivity (15 fmol/μL IgG), selectivity (1:200, molar ratio of IgG/BSA), loading capacity (200 mg/g) and recovery (106.4 ± 3.5%). In addition, the developed method based on Fe3O4@RF@Zr-BCP has been successfully applied to capture glycopeptides in tryptic digest of mouse teratoma cell extracts. It is worth emphasizing that compared with dispersed nanoparticles, the one-dimensional chain structure brings extraordinary reusability to Fe3O4@RF@Zr-BCP nanochains, which is conducive to the rapid cyclic enrichment of glycopeptides. This present work provides a potential enrichment platform for comprehensive glycoprotein analysis, and opens a new avenue for the application of oriented-assembly nanochains.

Magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from water samples using magnetic carbon nanofiber/MIL-101(Cr) nanocomposites

In this study, magnetic carbon nanofibers (Fe3O4@CNF) were modified with MIL-101(Cr) (Fe3O4@CNF@MIL-101) and used as sorbents for magnetic solid-phase extraction (MSPE) to extract polycyclic aromatic hydrocarbons (PAHs) from real water samples. Gas chromatography coupled with a flame ionization detector (GC-FID) was used for the determination of the PAHs. The effect of experimental variables on the extraction efficiency of PAHs was investigated and optimized. These variables include the quantity of sorbent, the kind and volume of the elution solvent, the duration of extraction and desorption, and the salt concentration. The linear range was found to be 0.01 to 200 ng mL-1 with correlation coefficients ranging from 0.9906 to 0.9931 after the effective extraction parameters were optimized. Its detection limits (LOD) were also calculated to be between 0.003 and 0.005 ng mL-1 (S/N = 3). The method's repeatability was tested at three different concentration levels (0.1, 1, and 10 ng mL-1), and relative standard deviations (RSDs%) were obtained in the range of 2.3 to 5.0%. Finally, using the MSPE-GC-FID method, PAHs were extracted from tap water, wastewater, seawater, and spring water samples. The relative recoveries were in the range of 95.7 to 99.8%.

Toxicity, formation, contamination, determination and mitigation of acrylamide in thermally processed plant-based foods and herbal medicines: A review

Thermal processing is one of the important techniques for most of the plant-based food and herb medicines before consumption and application in order to meet the specific requirement. The plant and herbs are rich in amino acids and reducing sugars, and thermal processing may lead to Maillard reaction, resulting as a high risk of acrylamide pollution. Acrylamide, an organic pollutant that can be absorbed by the body through the respiratory tract, digestive tract, skin and mucous membranes, has potential carcinogenicity, neurological, genetic, reproductive and developmental toxicity. Therefore, it is significant to conduct pollution determination and risk assessment for quality assurance and security of medication. This review demonstrates state-of-the-art research of acrylamide focusing on the toxicity, formation, contamination, determination, and mitigation in taking food and herb medicine, to provide reference for scientific processing and ensure the security of consumers.

Novel hydrocortisone magnetic molecularly imprinted polymers: Preparation, characterization, and application

In this work, magnetic molecularly imprinted polymers (MMIPs) were prepared by a surface imprinting method using Fe₃O₄ nanoparticles as a support. The products were characterized by FT-IR spectroscopy, VSM, TGA, SEM, and TEM. Combined with HPLC, hydrocortisone in milk powder and milk were separated and purified, and their contents were monitored. The results showed that MMIPs with a particle size of approximately 1000 nm were successfully prepared. The adsorption mechanism of MMIPs was confirmed by kinetic adsorption and thermodynamic adsorption experiments; the maximum adsorption capacity was found to be 17.2 mg g^-1, and adsorption equilibrium could be reached within 40 min. In the actual sample application, the recovery rates of milk powder and milk were 93.88-99.15% and 95.80-98.10%, respectively. These results showed that MMIPs had good performance in selectively identifying hydrocortisone and were suitable for determining hydrocortisone in milk products.

Study on Doxorubicin Loading on Differently Functionalized Iron Oxide Nanoparticles: Implications for Controlled Drug-Delivery Application

Nanoplatforms applied for the loading of anticancer drugs is a cutting-edge approach for drug delivery to tumors and reduction of toxic effects on healthy cells. In this study, we describe the synthesis and compare the sorption properties of four types of potential doxorubicin-carriers, in which iron oxide nanoparticles (IONs) are functionalized with cationic (polyethylenimine, PEI), anionic (polystyrenesulfonate, PSS), and nonionic (dextran) polymers, as well as with porous carbon. The IONs are thoroughly characterized by X-ray diffraction, IR spectroscopy, high resolution TEM (HRTEM), SEM, magnetic susceptibility, and the zeta-potential measurements in the pH range of 3-10. The degree of doxorubicin loading at pH 7.4, as well as the degree of desorption at pH 5.0, distinctive to cancerous tumor environment, are measured. Particles modified with PEI were shown to exhibit the highest loading capacity, while the greatest release at pH 5 (up to 30%) occurs from the surface of magnetite decorated with PSS. Such a slow release of the drug would imply a prolonged tumor-inhibiting action on the affected tissue or organ. Assessment of the toxicity (using Neuro2A cell line) for PEI- and PSS-modified IONs showed no negative effect. In conclusion, the preliminary evaluation of the effects of IONs coated with PSS and PEI on the rate of blood clotting was carried out. The results obtained can be taken into account when developing new drug delivery platforms.

Preparation of ethylenediamine-modified pectin/alginate/Fe3O4 microsphere and its efficient Pb2+ adsorption properties

As a common macromolecular carbohydrate, pectin has a strong affinity for Pb²⁺. An ethylenediamine modified pectin (EP₄₈) with 48 % of amidation was prepared and exhibited great removal efficiency towards Pb²⁺ in our previous study. However, the EP₄₈ has drawbacks in adsorption including low mechanical strength and difficulty in separation. In this study, EP₄₈ was compounded with sodium alginate (Alg) and Fe₃O₄ to synthesize EP₄₈/Alg/Fe₃O₄ microsphere. The physicochemical properties and Pb²⁺ adsorption characteristics of microsphere were analyzed. It was found that the microsphere exhibited good thermal stability, mechanical strength, porous structure, as well as acid tolerance. The pseudo-second-order model well described the kinetics of adsorption process, indicating the chemical adsorption is dominant. The Langmuir model fitted the experimental data well, and the maximum adsorption capacity reached 175.19 mg/g. Adsorption-desorption experiments showed that the removal rate of the microsphere maintained over 98.9 % after 10 cycles. The X-ray photoelectron spectroscopy (XPS) analyses revealed that the potential adsorption mechanism included ion-exchange and chelation. The above results suggested its potential use for the removal of Pb²⁺ from wastewater.

Ratiometric Fluorescent Metal-Organic Framework Biosensor for Ultrasensitive Detection of Acrylamide

Acrylamide is a neurotoxin and carcinogen that forms during the thermal processing of food, inflicting irreversible harm to human health. Herein, a ratiometric fluorescence biosensor based on a 6-carboxyfluorescein-labeled aptamer (FAM-ssDNA) and porphyrin metal-organic framework (PCN-224) was developed. PCN-224 exhibits strong adsorption capacity for FAM-ssDNA and also quenches the fluorescence of FAM-ssDNA via fluorescence resonance energy transfer and photoinduced electron transfer. FAM-ssDNA hybridizes with complementary DNA to form double-stranded DNA (FAM-dsDNA), which is liberated from the PCN-224 surface, resulting in fluorescence recovery. However, the intrinsic fluorescence of the ligand remains unchanged. Acrylamide can create an adduct with FAM-ssDNA and inhibit the hybridization of FAM-dsDNA, thus realizing ratiometric sensing of acrylamide. The proposed biosensor displays excellent detection performance from 10 nM∼0.5 mM with a limit of detection of 1.9 nM. In conclusion, a fabricated biosensor was successfully applied to detect acrylamide in thermally processed food, and the results were consistent with those of high-performance liquid chromatography.

A fluorescence biosensor based on double-stranded DNA and a cationic conjugated polymer coupled with exonuclease III for acrylamide detection

As a toxic substance on human health produced in food thermal treatment, simple analytical approaches are highly desired for the detection of acrylamide (ACR) in foods. With the aid of exonuclease III (Exo III), a simple fluorescence sensor was proposed based on carboxyfluorescein-labeled double-stranded DNA (FAM-dsDNA) and a cationic conjugated polymer (PFP). Fluorescence resonance energy transfer (FRET) efficiency between FAM and PFP was changed with and without ACR. When ACR was present, ACR and single-stranded DNA (P1, ssDNA) formed an adduct, allowing free FAM-labeled complementarity strand DNA (P2, FAM-csDNA) to appear in the solution and avoiding the digestion of P2 by Exo III. After the addition of PFP, the interaction of PFP and FAM induced strong FRET. Under optimized conditions, ACR was detected with a limit of detection (LOD) of 0.16 μM. According to this biosensor, a LOD of 1.3 μM in water extract samples was observed with a good recovery rate (95-110 %).

A portable kit based on thiol-ene Michael addition for acrylamide detection in thermally processed foods

Accurate, sensitive, and selective analysis of acrylamide generated in thermally processed foods is of great significance for food safety. Herein, a novel acrylamide sensing platform is designed for both sensitive on-site colorimetric analysis and accurate UV-vis spectroscopy quantification, by integrating thiol-ene Michael addition with gold nanoparticles-mediated catalytical oxidation. The Michael addition reaction between acrylamide and glutathione efficiently alleviates glutathione-induced catalytic activity inhibition of gold nanoparticles, evoking the chromogenic reaction of H₂O₂-mediated 3,3',5,5'-tetramethylbenzidine. With increasing the concentration of acrylamide, the oxidation of 3,3',5,5'-tetramethylbenzidine is accelerated, presenting a series of shades from colorless to blue. The sensing platform exhibits excellent detection performance of acrylamide in the range of 0.5-175 μM with a detection limit of 0.16 μM, and is successfully employed in food samples. Especially, a portable assay kit based on the proposed platform is developed for visual determination of acrylamide, opening an avenue for smart sensors of food safety hazards.

Molecular imprinting technology and poly (ionic liquid)s: Promising tools with industrial application for the removal of acrylamide and furanic compounds from coffee and other foods

Coffee is one of the most consumed beverages in the world. Coffee provides to the consumer special sensorial characteristics, can help to prevent diseases, improves physical performance and increases focus. In contrast, coffee consumption supplies a significant source of substances with carcinogenic and genotoxic potential such as furan, hydroxymethylfurfural (HMF), furfural (F), and acrylamide (AA). The present review addresses the issues around the presence of such toxic substances formed in Maillard reaction (MR) during thermal treatments in food processing, from chemical and, toxicological perspectives, occurrences in coffee and other foods processed by heating. In addition, current strategies advantages and disadvantages are presented along with application of molecular imprinting technology (MIT) and poly (ionic liquid) s (PIL) as an alternative to reduce the furan, HMF, F and AA content in coffee and other foods.

Design, Preparation, and Application of Magnetic Nanoparticles for Food Safety Analysis: A Review of Recent Advances

This review (with 126 references) aims at providing an updated overview of the recent developments and innovations of the preparation and application of magnetic nanoparticles for food safety analysis. During the past two decades, various magnetic nanoparticles with different sizes, shapes, and surface modifications have been designed, synthesized, and characterized with the prospering development of material science. Analytical scientists and food scientists are among the ones who bring these novel materials from laboratories to commercial applications. Powerful and versatile surface functional groups and high surface to mass ratios make these magnetic nanoparticles useful tools for high-efficiency capture and preconcentration of certain molecules, even when they exist in trace levels or complicated food matrices. This is why more and more methods for sensitive detection and quantification of hazards in foods are developed based on these magic magnetic tools. In this review, the principles and superiorities of using magnetic nanoparticles for food pollutant analysis are first introduced, like the mechanism of magnetic solid phase extraction, a most commonly used method for food safety-related sample pretreatment. Their design and preparation are presented afterward, alongside the mechanisms underlying their application for different analytical purposes. After that, recently developed magnetic nanoparticle-based methods for dealing with food pollutants such as organic pollutants, heavy metals, and pathogens in different food matrices are summarized in detail. In the end, some humble outlooks on future directions for work in this field are provided.

Sensitive and selective determination of imidacloprid with magnetic molecularly imprinted polymer by using LC/Q-TOF/MS

In this paper, magnetic-molecularly imprinted polymer was used for the preconcentration of trace levels of imidacloprid in water and apple samples prior to liquid chromatography-quadrupole-time-of-flight mass spectrometric determination. The selectivity of the magnetic polymer was united with the sensitivity and the high resolving power of the chromatographic system. The developed method showed a linear range from 10.0 to 500.0 µg/L. The quantitative recoveries were obtained for water and apple samples in the range of 92.0%–99.0 %. The relative standard deviations of intra-day and inter-day tests were found to be in the range of 0.8%–1.2% and 1.2%–1.6 %, respectively. In addition, the same magnetic-molecularly imprinted polymer (MMIP) can be used at least ten cycles for the determination of imidacloprid. The preconcentration factor of the method was found to be 2.5, and the total preconcentration procedure can be completed in 1 h. Characterization of synthesised particles were executed with various techniques. Due to its suitable limit of detection, dynamic linear range, sensitivity and selectivity, the developed method seemed to be ideal for the determination and preconcentration of imidacloprid in water and fruit samples.

Comparison and recent progress of molecular imprinting technology and dummy template molecular imprinting technology

Molecular imprinting technology for the preparation of polymers with specific molecular recognition function had become one of the current research hotspots. It has been widely applied in chromatographic separation, antibody and receptor mimetics, solid-phase extraction, bio-sensors, and other fields in the last decades. In this study, molecular imprinting technology was summarized from the points of templates and dummy templates, and four typical target analytes were selected to compare the differences between templates and dummy templates. The current status and prospects of molecular imprinting technology were also proposed.

Highly effective pre-concentration of thymol and carvacrol using nano-sized magnetic molecularly imprinted polymer based on experimental design optimization and their trace determination in summer savoury, Origanum majorana and Origanum vulgare extracts

To ascertain thymol and carvacrol in pharmaceutical syrups, a valid and effective magnetic molecular imprinted polymer dispersive solid phase microextraction (MMIP-DSPME) process was developed in this study, which was in combination with a high performance liquid chromatography-ultra violet (HPLC-UV) technique for the assessment of thymol and carvacrol separation and pre-concentration. Contact time, eluent kind and volume, pH, the mass of the MMIP were all taken into consideration as key factors. Design expert and multi-objective response surface methodology (RSM) were used to optimize these variables. The mass of the MMIP, sample pH, eluent kind, time of sorption, the volume of eluent, and time of elution were 10 mg, 6, acetonitrile, 28 min, 200 µL, and 5.5 min, respectively, for the maximum extraction recovery of the analytes. The limit of detection (LOD) was 0.042 ng mL^-1 at the optimal conditions, while the value for the limit of quantification (LOQ) was 0.140 ng mL^-1. At the optimized conditions for thymol and carvacrol, the suggested MMIP sorbent had sorption capacities of 64.1 and 72.6 mg g^-1, respectively. Furthermore, for triplicate measurements, the linear dynamic range (LDR) was 0.40-5000 ng mL^-1, and the method's accuracy (RSD %) was 6.26%. The saturation magnetization for the MMIP was 19.0 emu g^-1 obtained by VSM, allowing the sorbent to be separated quickly. The sorption experiments confirmed the large sorption capacity of the MMIP for thymol and carvacrol, as well as its homogeneous binding sites. The extraction recovery for thymol and carvacrol was 96.9-103.8% and 96.6-105.4%, respectively, at all spiked amounts (20, 100, 200, and 500 ng mL^-1). The findings of seven desorption-regeneration cycles using MMIP demonstrated the high stability of the sorbent. The MMIP revealed a particular behavior of sorption for thymol and carvacrol, implying a selective, simple, effective, and flexible analytical method.

Preparation of a molecularly imprinted test strip for point-of-care detection of thiodiglycol, a sulfur mustard poisoning metabolic marker

Conventional methods for the detection of the sulfur mustard poisoning metabolic marker, thiodiglycol (TDG), require expensive instruments and reagents as well as professional operators. To address these problems, a novel test strip based on a molecularly imprinted sensitive membrane (MIM) was developed in this work for point-of-care (POC) detection of TDG. The TDG test strip was prepared conveniently by coating molecular imprinted polymers (MIPs) on a nitrocellulose membrane. When the sample contained TDG, the MIPs could specifically bind with TDG. A great number of AuNPs (AuNPs) could then be adsorbed on the test strip via the formation of an Au-S bond between TDG and AuNPs, giving the test strip the obvious red color of AuNPs. In the absence of TDG, the test strip exhibited much lighter color because it could not adsorb AuNPs. By monitoring the color change of the test strip, TDG could be detected from 1.0 ng/mL to 100.0 μg/mL with a detection limit of 0.23 ng/mL (3σ) under the optimal conditions (the molar ratio of TDG to MAA was 1:2; the eluent was chloroform; the elution time was 50 min; the reaction time between MIPs and TDG was 15 min; the adsorption time of AuNPs was 40 min; the temperature of the reaction system was 35 °C). This method has excellent selectivity and has been used to detect TDG in urine, showing great potential for POC detection of TDG in clinical samples.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.

Recent advances and applications of cyclodextrins in magnetic solid phase extraction

Cyclodextrins (CDs) as a family of cyclic oligosaccharides are toroidal with a hydrophobic interior and a hydrophilic exterior. They are well-known for their ability to form host-guest inclusion complexes with different compounds. They are used as chiral stationary phases in high performance liquid chromatography (HPLC) and gas chromatography (GC) or as chiral reagents in the background electrolyte of capillary electrophoresis (CE). In recent years, they have been used for modification of sorbents or as sorbents in solid phase extraction (SPE) procedures. Magnetic solid-phase extraction (MSPE), as a new type of SPE procedure, has received considerable attention due to its rapid phase separation process as compared to traditional extraction mode. This review covers the synthesis of CD-based magnetic sorbents (such as immobilization of CDs onto the different supports, production of nanosponges, and making hybrid substances with nanomaterials) and the use of these compounds in MSPE of different analytes from biological, environmental, and food samples. Also, prospects of CD-based sorbents for sample pre-treatment are also proposed.

Improved solid phase extraction for selective and efficient quantification of sunset yellow in different food samples using a novel molecularly imprinted polymer reinforced by Fe3O4@UiO-66-NH2

The overuse of synthetic dyes in food products has gradually increased in recent years, resulting food safety and human health has become a global issue. An innovative design of a magnetic molecularly imprinted polymer (Fe3O4@UiO-66-NH2@MIP) for efficient, fast, and selective determination of sunset yellow (SY) from different food products was described in this study. The absorption properties of Fe3O4@UiO-66-NH2@MIP were elucidated by adsorption kinetics, isotherms, reusability, and selectivity experiments. Because of the incorporation of porous Fe3O4@UiO-66-NH2nanocomposite into molecularly imprinted polymer an efficient nanosorbent with a short equilibrium time, a high adsorption capacity, and a good imprinting factor was finally obtained. The porous Fe3O4@UiO-66-NH2@MIP are also used for quantification of the SY. Under optimal conditions, good linearity (R2 0.9964) in the range of 1.0-120 mg L-1 and a low limit of detection (0.41 mg L-1) was observed with satisfactory recoveries (92.50-106.1%) and excellent reusability (RSD ≤ 6.6% after 12 cycles).

Biosensing platform on ferrite magnetic nanoparticles: Synthesis, functionalization, mechanism and applications

Ferrite magnetic nanoparticles (FMNPs) are gaining popularity to design biosensors for high-performance clinical diagnosis. The fusion of information shows that FMNPs based biosensors require well-tuned FMNPs as detection probes to produce large and specific biological signals with minimal non-specific binding. Nevertheless, there is a noticeable lacuna of information to solve the issues related to suitable synthesis route, particle size reduction, functionalization, sensitivity towards targeted intercellular biological tiny particles, and lower signal-to-noise ratio. Therefore it allows exploring unique characteristics of FMNPs to design a suitable sensing device for intracellular measurements and diseases detection. This review focuses on the extensively used synthesis routes, their advantages and limitations, crystalline structure, functionalization, along with recent applications of FMNPs in biosensors, taking into consideration their analytical figures of merit and range of linearity. This work also addresses the current progress, key factors for sensitivity, selectivity and productivity improvement along with the challenges, future trends and perspectives of FMNPs based biosensors.

Preparation and characterization of a chiral molecularly imprinted polymer with a novel functional monomer for controlled release of S-sulpiride

A novel molecularly imprinted polymer (MIP) with chiral recognition affinity to S-sulpiride (S-SUL) enantiomer was prepared by using newly synthesized N-acryloyl-tryptophan (ATrp) as function monomer, S-SUL as the template molecule, and ethyleneglycol dimethacrylate (EGDMA) as the cross linker. Under the optimized synthesis conditions, the MIP was synthesized by bulk polymerization according to the molar ratio of 1:4 of S-SUL to ATrp, and structurally characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and laser particle analysis. The results illustrated that the MIP offered uniform, loose and porous structure. The adsorption performance of the MIP was evaluated by the isotherm and kinetic models, and the adsorption isotherm conformed to the Freundlich model. The maximum adsorption capacity, selectivity factor and enantioselectivity coefficient to S-SUL were respectively 226.2389 µmol/g, 2.34 and 11.66. Based on the chiral recognition specificity, the drug release experiments demonstrated that the MIP as controlled and sustained release carrier could inhibit the release rate of S-enantiomer compared to the tablet without the MIP, exhibiting the potential of the MIP synthesized in chiral drug delivery.

[Recent advances in applications of fragment/dummy molecularly imprinted polymers]

Molecularly imprinted polymers (MIPs) are designed to mimic the specific binding principle of enzymes to substrates or antigens to antibodies, while holding several advantages such as structure predictability, recognition specificity, easy preparation, low cost, high physical robustness, and thermal stability. Therefore, they have been widely applied in many fields including sample preparation (pretreatment), sensing analysis (chemo/biosensors), biomedicine, and environment/food analysis. To date, several strategies were developed for MIPs preparation, aiming to simplify the preparation process and/or improve the properties of the polymers, greatly broadening its usability. The exploration in various advanced imprinting strategies and their combinational use has become a research hotspot in MIPs preparation, among which the fragment imprinting strategy and the dummy template imprinting strategy are especially favored. Fragment imprinting, also called segment imprinting, uses a partial structure of the target molecule as a pseudo-template to prepare MIPs. This strategy is useful to target molecules that are not easy to obtain or that are too large to be used as templates, providing a feasible method for imprinting target analytes that are easy to inactivate or infect, as well as macromolecules that are difficult to imprint. In turn, dummy template imprinting uses molecules with structure, shape, and size similar to the target analytes as templates for imprinting. Because the target is not directly used as a template, this strategy can overcome problems of template leakage, as well as solve target molecule-related difficulties as they can be expensive, infectious, flammable, explosive, or chemically instable. This mini-review compiles information of several articles published in the last four years across ACS, Elsevier, RSC, and other databases, summarizing the most recent advances in the application of fragment/dummy template MIPs (FMIPs/DMIPs). Herein, the biomedical application of FMIPs is mainly addressed as a strategy for the detection of proteins and microorganisms, and the application of FMIPs in the field of food analysis is also explored. In recent years, the imprinting of mammalian cells has made some progress in the application of FMIPs. Mammalian cells, especially cancer cells, overexpress some proteins and sugars, which are good fragment templates. Consequently, the fragment imprinting strategy is widely used in cancer cell imaging, localization, and treatment. Moreover, due to the complicated structure and easy inactivation of some proteins, their MIPs are often prepared by fragment imprinting (also called epitope imprinting). As some microorganisms are infectious, imprinting microorganisms directly can pose a risk; therefore it is safer to also use the fragment imprinting strategy in such cases. The recent application of fragment imprinting strategy in other areas remains scarce. Nonetheless, three studies in the food analysis have explored this possibility. DMIPs are widely used in sample pretreatment and sensing analysis, and they are mainly used as SPE adsorbents for packed SPE, dispersive SPE (DSPE), magnetic SPE (MSPE), and matrix solid phase dispersion (MSPD) extraction. In addition, DMIPs are employed as molecularly imprinted membrane materials. As a result, by virtue of DMIPs, selective extraction and enrichment of target analytes from complicated samples can be achieved. MIP-based sensors can either recognize or transduce, meaning that they can specifically recognize and bind target analytes as well as generate output signals for detection. Because of the high selectivity of MIPs, the use of a dummy template imprinting strategy solves the problem of template leakage in the process of recognition and adsorption, further improving the detection accuracy and sensitivity of the sensor. These features expand the application range of MIP-based sensors. This review briefly overviews the construction and application of chemiluminescence and fluorescence sensors based on DMIPs. Lastly, the advantages and disadvantages, differences, and relationships among the two strategies are summarized. Despite of their potential, four main challenges still remain as major setbacks for the application of FMIPs and DMIPs: (i) the difficulty to select or prepare appropriate fragment templates and dummy templates; (ii) how to ensure that there is almost no difference in the recognition adsorption selectivity between the fragment/dummy template and the original template, so as to ensure optimal recognition specificity; (iii) the use of, environment-friendly reagents to reduce pollution during FMIPs/DMIPs preparation and use to conform with green chemistry requirements; (iv) how to strengthen the industrial and commercial applications of FMIPs and DMIPs. Therefore, significant efforts should be made to develop new imprinting strategies and techniques, as well as to adopt combinational imprinting approaches for FMIPs/DMIPs preparation to expedite the sustainable development and efficient application of FMIPs and DMIPs.

Fluorescence assay of oxytetracycline in seawater after selective capture using magnetic molecularly imprinted nanoparticles

A comprehensive strategy for manufacturing a novel sorbent based on magnetic molecularly imprinted polymers (MMIPs) is addressed for selective capture of oxytetracycline from seawater. The novel MMIPs were synthesized by nano-Fe₃O₄ as sacrificial matrix and adsorption properties of the polymers demonstrate rapid adsorption kinetics, high adsorption capacity, and specificity towards oxytetracycline provided by the core-shell composite structure. After screening the critical parameters by multivariate optimization, a magnetic imprinting solid phase extraction method combined with fluorescence spectrophotometry (MMIP-SPE-FL) was constructed for sensitive determination of oxytetracycline in seawater samples. The results show a good linear response dependence on the spiking concentration of 3-100 μg L^-1, and a satisfactory limit of detection of 0.7 μg L^-1 after the MMIP-SPE preconcentration. Seven seawater samples from Jiaozhou bay were analyzed to give recoveries in the range of 89.75-107.65% with relative standard deviation values of less than 5.44% (n = 3).

Magnetic boron nitride nanosheets as a novel magnetic solid-phase extraction adsorbent for the determination of plant growth regulators in tomatoes

A novel magnetic boron nitride nanosheets (Fe₃O₄@BNNSs) composite-based magnetic solid-phase extraction (MSPE) method was employed to analyse six plant growth regulators (PGRs) in tomatoes combined with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The novel Fe₃O₄@BNNSs composite was prepared via an in situ chemical coprecipitation process and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). Several factors that may affect the extraction efficiencies were optimized. Under the optimal factors, low limits of detection (0.002-0.010 ng g^-1), good linear ranges (0.05-10 ng g^-1) and satisfactory precisions (intra-day: 1.2%-3.9%; inter-day: 2.1%-6.9%) were achieved. The established approach was successfully employed to extract and determine PGRs in tomatoes, and the spiked recoveries were between 85.2 and 109.0%.

Recent Applications of Magnetic Nanoparticles in Food Analysis

Nanotechnology has become a topic of interest due to the outstanding advantages that the use of nanomaterials offers in many fields. Among them, magnetic nanoparticles (m-NPs) have been one of the most widely applied in recent years. In addition to the unique features of nanomaterials in general, which exclusively appear at nanoscale, these present magnetic or paramagnetic properties that result of great interest in many applications. In particular, in the area of food analysis, the use of these nanomaterials has undergone a considerable increase since they can be easily separated from the matrix in sorbent-based extractions, providing a considerable simplification of the procedures. This allows reducing cost and giving fast responses, which is essential in the food trade to guarantee consumer safety. These materials can also be easily tunable, providing higher selectivity. Moreover, their particular electrical, thermal and optical characteristics allow enhancing sensor signals, increasing the sensitivity of the approaches based on this type of device. The aim of this review article is to summarise the most remarkable applications of m-NPs in food analysis in the last five years (2016–2020) showing a general view of the use of such materials in the field.