Molecularly imprinted covalent organic polymers for the selective extraction of benzoxazole fluorescent whitening agents from food samples

Design, synthesis, and cytotoxicity of ibuprofen-appended benzoxazole analogues against human breast adenocarcinoma

A library of novel ibuprofen-appended benzoxazole analogues (7a-l) was synthesized via a series of nitration, reduction, and condensation-cyclization reactions and screened for their in vitro anticancer activity against human breast cancer MCF-7 and MDA-MB-231 cell lines using doxorubicin as a standard reference. Compounds 7h and 7j displayed outstanding activity against the MCF-7 cell line with an IC50 value of 8.92 ± 0.91 μM and 9.14 ± 8.22 μM, respectively, compared to the doxorubicin IC50 value of 9.29 ± 1.02 μM. Compound 7h also exhibited outstanding activity against the MDA-MB-231 cell line with an IC50 value of 7.54 ± 0.95 μM compared to the doxorubicin IC50 value of 7.68 ± 5.36 μM. Compounds 7h, 7i, 7j, and 7g showed identical morphological changes to those showed by doxorubicin. The molecular docking study against ERα unveiled their best docking scores and binding interactions in agreement to experimental results. Pharmacokinetics prediction envisaged their drug-like properties suitable for therapeutic applications.

Conjugated hypercrosslinked polymers imprinted with 3,5-dinitrosalicylic acid for the fluorescent determination of α-amylase activity

The discovery of a series of coupling reactions between various building blocks has driven the development of porous organic polymers, but the common usage of expensive and air-sensitive organometallic catalysts and complex procedures in harsh syntheses has limited their expansion. A microporous hypercrosslinked polymer (HCP) was synthesized by polymerizing a naphthalene monomer and a 1,4-dimethoxybenzene crosslinker using Friedel-Crafts alkylation over an FeCl₃ catalyst and imprinted with 3,5-dinitrosalicylic acid (DNS). The DNS-molecularly-imprinted HCPs (MIHCPs) were characterized as having IUPAC Type I mesoporosity, a specific surface area of 1134 m² g^-1, a monolayer adsorption capacity of 116 cm² g^-1, pore sizes ranging from 5 to 8.5 Å, amorphous frameworks, and distinctive absorption and emission bands by N₂ adsorption/desorption analyses, scanning and transmission electron microscopies, and FTIR, UV-Vis, and fluorescence spectrometries. The π-conjugated imprinted framework endowed the MIHCPs with 405-nm fluorescent emission at a 330-nm excitation and dynamic quenching, which was confirmed by changes in fluorescence lifetime and followed a linear Stern-Volmer plot against 1.0-200 μM DNS template molecules under optimized conditions of a pH 7.0 buffer, an MIHCP concentration of 125 μg mL^-1, and a 3.0-min equilibration time. The MIHCPs exhibited a high imprinted factor of 8.7 against nonimprinted HCP and a selectivity of 8.63 against reduced DNS, which enabled fluorometric detection of DNS molecules produced by the hydrolysis of starch with microbial, salivary, and pancreatic α-amylases and the subsequent redox incubation with the DNS oxidant. The fluorometric measurement of α-amylase activity was higher in accuracy and precision (RSD: 2.6-2.8% vs. 3.9-4.0%) than conventional UV-Vis spectrometry because the excellent fluorescent sensitivity and imprinting selectivity of the MIHCP probes enabled the use of higher dilution factors with weaker matrix effects.

Fluorescence determination of tannic acid imprinted in conjugated hypercrosslinked polymers by Friedel-Crafts acylation

A molecularly imprinted hypercrosslinked polymer (HCP) was synthesized from the polymerization of mesitylene monomer, terephthaloyl chloride crosslinker, and tannic acid (TA) template through FeCl₃-catalyzed Friedel-Crafts acylation. The TA-imprinted HCP (TAHCP) was capable of IUPAC Type I mesoporosity, with specific surface area of 1258 m² g^-1, monolayer adsorption capacity of 289 cm² g^-1, pore sizes ranging from 4.4 to 12.6 Å, amorphous morphology, and characteristic absorption and emission bands. The extended π-conjugation framework of TAHCP was endowed with 385-nm fluorescent emission at 310-nm excitation. The fluorescence intensity of TAHCP could be dynamically quenched by TA and was linearly correlated with 20-1000 nM TA concentrations on the Stern-Volmer plot in the optimized conditions of pH 5.5 buffer, 100 μg mL^-1 TAHCP, and 3.5 min equilibrium. The relative standard deviation (RSD) for 50 nM TA was 3.4% (n = 5), and the limit of detection was 6.2 nM based on the 3σ of the TA blanks). For 50nM TA, the imprinted factor was calculated to be 7.8, and the selectivity for 250 nM interferents, including ions, organic acids, saccharides, amino acids, and caffeine, which are commonly found in beverages, was 7.5-9.5, except for gallic acid (1.2). The recoveries of TA spiked in tea and juice beverages at three levels (10-150 nM) were 93.6-101.9% (RSD = 3.6-4.3%).

Auto-fluorescence of cellulose paper with spatial solid phrase dispersion-induced fluorescence enhancement behavior for three heavy metal ions detection

Auto-fluorescence of cellulose paper is often considered as an interfering fluorescence, which directly impedes the cellulose paper as a substrate material. This paper creatively explored the composition and properties of auto-fluorescence, and lignosulfonate was primarily speculated as the main source of auto-fluorescence. Surprisingly, its spatial solid phrase dispersion-induced fluorescence enhancement behavior was found. Then, cellulose paper was modified with Mn-doped ZnS quantum dots, and the prepared ratiometric fluorescent paper chip has good performances on morphology, stability, and fluorescence properties. Besides, the paper chip exhibited different fluorescence responses to three heavy metal ions in water sample. The limit of detection for Cd²⁺, Hg²⁺ and Pb²⁺ reached 1.61 nM, 0.01 nM, and 0.02 nM, respectively. In short, the molecular simulation results theoretically proved that heavy metal ions owned substitution affinity with lignosulfonate. Ultimately, this study was the first attempt to utilize paper-based auto-fluorescence, which could better accelerate the development of paper-based chips.

Application of an improved hollow fiber liquid phase microextraction technique coupled to LC-MS/MS to studying migration of fluorescent whitening agents from plastic food contact materials

In this paper, a new hollow fiber liquid-phase microextraction method was developed to improve the extraction of five fluorescent whitening agents that migrated from plastics food contact materials. Influencing factors, such as the types of membrane, the extraction solvent, the stirring speed, the addition of salt ion, and extraction time, were investigated in detail. Under the optimal conditions, high enrichment factors (71-205) can be obtained with 15 μL extraction solvent. The new method is advantageous; the polypropylene hollow fiber membrane modified by sepiolite nanoparticles had excellent solvent binding force and mass transfer effect compared with the conventional extraction technique. The extracts were analyzed by high performance liquid chromatography-tandem mass spectrometry, the limits of detection were 0.3 or 0.9 ng kg^-1 with good correlation coefficients (r² ≥ 0.9940) for the five fluorescent whitening agents. The intra-day and inter-day recoveries ranged between 82.6% and 112%, with a relative standard deviation of less than 12%. The established method was successfully applied to the analysis of fluorescent whitening agent migration from four types of plastic food contact materials immersed in three food simulants.

Amino functionalized magnetic covalent organic framework for magnetic solid-phase extraction of sulfonylurea herbicides in environmental samples from tobacco land

An amino-functionalized magnetic covalent organic framework composite TpBD-(NH2 )2 @Fe3 O4 (Tp=Tp1,3,5-triformylphloroglucinol, BD-(NH2 )2 is 3,3',4,4'-biphenyltetramine) was prepared by post-synthesis modification. Due to its abundant benzene rings and amino groups, large specific surface area and porous structure, the prepared TpBD-(NH2 )2 @Fe3 O4 exhibits high extraction efficiency toward sulfonylurea herbicides. Based on this, a new method of magnetic solid-phase extraction with TpBD-(NH2 )2 @Fe3 O4 as the sorbent combined with high-performance liquid chromatography and ultraviolet detection was developed for trace analysis of sulfonylurea herbicides in environmental water, soil and tobacco leaves samples from tobacco land. Under the optimized conditions, the limits of detection within 0.05-0.14 μg/L were achieved with a high enrichment factor of 217-260-fold, and the relative standard deviations were 4.9-7.5% (n = 7, c = 0.5 μg/L). The linear range was around three orders of magnitude with the square of correlation coefficient higher than 0.9936. The method was applied to analyze five sulfonylurea herbicides in the environmental water, soil, and tobacco leave samples collected from tobacco land. No sulfonylurea herbicides were detected in these samples. The recoveries of target sulfonylurea herbicides in spiked environmental water, soil, and tobacco leaf samples were found in the range of 90.7-104, 70.7-99.0, and 59.3-97.8%, respectively. The results illustrate that the established TpBD-(NH2 )2 @Fe3 O4 -magnetic solid-phase extraction- high-performance liquid chromatography-ultraviolet detection method is efficient for the analysis of trace sulfonylurea herbicides in environmental samples.

[Synthesis and application progress of covalent organic polymers in sample preparation for food safety analysis]

食品安全关系身体健康和生命安全,是全球关注的热点之一。食品基质复杂,痕量有毒有害物质分析之前必须经过有效的前处理。目前发展的前处理技术如固相萃取、磁固相萃取、固相微萃取等,其关键是吸附介质。共价有机聚合物是一类通过共价键连接而成的有机多孔材料,具有质轻、稳定性好、比表面积大、结构可控、易于修饰等特性,是一类优异的新型吸附材料。该文综述了近年来共价有机聚合物(COPs)在食品安全分析前处理中的应用进展。共价有机聚合物及其功能化复合材料通过简单的装填、聚合反应或化学键合固定到小柱或毛细管柱中用作固相萃取的吸附介质;通过一锅法、原位还原法、原位生长法或共沉淀法生成具有磁性的固相萃取吸附介质;或者通过物理涂覆、化学键合、溶胶凝胶法及原位生长法制备固相微萃取纤维。基于以上高吸附容量共价有机聚合物的样品前处理技术,食品中农残兽残、添加剂、环境污染物及生物毒素等得到了有效富集。最后,展望了COPs在食品分析样品前处理应用中的发展方向:简单高效绿色制备方法的开发,功能化COPs的设计合成;萃取机理的研究;高通量、高灵敏度分析方法研究。这些研究将促进COPs在样品前处理领域获得更广泛的应用。

Recent advances and applications of molecularly imprinted polymers in solid-phase extraction for real sample analysis

Sample pretreatment is essential for the analysis of complicated real samples due to their complex matrices and low analyte concentrations. Among all sample pretreatment methods, solid-phase extraction is arguably the most frequently used one. However, the majority of available solid-phase extraction adsorbents suffer from limited selectivity. Molecularly imprinted polymers are a type of tailor-made artificial antibodies and receptors with specific recognition sites for target molecules. Using molecularly imprinted polymers instead of conventional adsorbents can greatly improve the selectivity of solid-phase extraction, and therefore molecularly imprinted polymer-based solid-phase extraction has been widely applied to separation, clean up and/or preconcentration of target analytes in various kinds of real samples. In this article, after a brief introduction, the recent developments and applications of molecularly imprinted polymer-based solid-phase extraction for determination of different analytes in complicated real samples during the 2015-2020 are reviewed systematically, including the solid-phase extraction modes, molecularly imprinted adsorbent types and their preparations, and the practical applications of solid-phase extraction to various real samples (environmental, food, biological, and pharmaceutical samples). Finally, the challenges and opportunities of using molecularly imprinted polymer-based solid-phase extraction for real sample analysis are discussed.

Sulfonate-bonded covalent organic polymer as mixed-mode sorbent for on-line solid-phase extraction of ß2-receptor agonists

A novel sulfonate-bonded covalent organic polymer (COP_TPBA-BPDA@SA) with mixed-mode interactions of hydrophobic and cation-exchange was synthesized and exploited as sorbent for on-line solid-phase extraction (on-line SPE) of ß₂-receptor agonists. The successful synthesis of COP_TPBA-BPDA@SA was confirmed by the characterization of SEM, XPS and FT-IR. Due to the excellent mixed-mode extraction ability towards the positively charged ß₂-receptor agonists and the good anti-interference performance, COP_TPBA-BPDA@SA was introduced into on-line SPE-HPLC system for selective extraction of ß₂-receptor agonists in pork and pork liver. Via the optimization of the extraction condition, including formic acid percentage and ACN percentage in the sampling solution, the mixed-mode extraction mechanism of COP_TPBA-BPDA@SA was investigated. The elution condition, such as the pH value, formic acid percentage and ACN percentage of the eluent was also optimized for the desired SPE performance. Under the optimized condition, COP_TPBA-BPDA@SA revealed better purification performance than COP_TPBA-BPDA without sulfonating. The LODs for ß₂-receptor agonists were in the range of 0.08-0.22 μg/kg, and the recoveries in different samples at three spiked levels (0.4, 4.0, 8.0 μg/kg) were ranged from 83.2% to 98.5% with RSDs less than 5.2%, which indicated the satisfactory mixed-mode extraction ability of COP_TPBA-BPDA@SA as well as the good applicability of the developed method.

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.

Quaternary ammonium salt ion pair reagent sensitizing for determination of fluorescence whitening agent 85 in paper food packaging

Fluorescent whitening agents (FWAs) are added to food packaging during manufacture to improve the whiteness and brightness. It is of great significance to develop a fast and sensitive FWAs detection method because their potential hazards to human health. Herein, we found that the quaternary ammonium salt ion pair reagents could enhance the fluorescence of FWAs, and then developed a fluorescent determination method for FWA 85 in paper food packaging. Under the optimized conditions, the linear range for the determination of FWA 85 was 5-200 ng/mL (R² = 0.9996). The limit of detection was 1.20 ng/mL (S/N = 3) and the limit of quantitation was 3.99 ng/mL. The analytical feasibility was investigated further via determination of FWA 85 in paper food packing, which shows the recoveries were varied from 83.84% to 115.29% with RSDs from 1.64% to 7.22%. The method provides a new quaternary ammonium salt ion pair reagent sensitization for the detection of FWAs in paper food packaging.

Assembly and application advancement of organic-functionalized graphene-based materials: A review

Owing to the remarkable physicochemical properties such as hydrophobicity, conductivity, elasticity, and light weight, graphene-based materials have emerged as one of the most appealing carbon allotropes in materials science and chemical engineering. Unfortunately, pristine graphene materials lack functional groups for further modification, severely hindering their practical applications. To render graphene materials with special characters for different applications, graphene oxide or reduced graphene oxide has been functionalized with different organic agents and assembled together, via covalent binding and various noncovalent forces such as π-π interaction, electrostatic interaction, and hydrogen bonding. In this review, we briefly discuss the state-of-the-art synthetic strategies and properties of organic-functionalized graphene-based materials, and then, present the prospective applications of organic-functionalized graphene-based materials in sample preparation.

Agaricus bisporus and its by-products as a source of valuable extracts and bioactive compounds

Edible mushrooms constitute an appreciated nutritional source for humans due to their low caloric intake and their high content in carbohydrates, proteins, dietary fibre, phenolic compounds, polyunsaturated fatty acids, vitamins and minerals. It has been also demonstrated that mushrooms have health-promoting benefits. Cultivation of mushrooms, especially of the most common species Agaricus bisporus, represents an increasingly important food industry in Europe, but with a direct consequence in the increasing amount of by-products from their industrial production. This review focuses on collecting and critically investigating the current data on the bioactive properties of Agaricus bisporus as well as the recent research for the extraction of valuable functional molecules from this species and its by-products obtained after industrial processing. The state of the art regarding the antimicrobial, antioxidant, anti-allergenic and dietary compounds will be discussed for novel applications such as nutraceuticals, additives for food or cleaning products.

A hybrid triazine-imine core-shell magnetic covalent organic polymer for analysis of pesticides in fruit samples by ultra high performance liquid chromatography with tandem mass spectrometry

A novel hybrid triazine-imine core-shell magnetic covalent organic polymer with high adsorption capacity and excellent stability was fabricated by surface-assisted in situ growth technique. The composite possesses porous and extended π-conjugated system, and was applied as the magnetic sorbent for efficient enrichment and rapid separation of pesticides. A new analytical method for simultaneous determination of eight pesticides in fruit samples was developed by magnetic solid phase extraction combined with ultra high performance liquid chromatography and tandem mass spectrometry. The effect of extraction time, desorption time, and the type of desorption solvent on the extraction efficiency were evaluated. The established method shows good repeatability and high sensitivity. The repeatability of this method was estimated with relative standard deviations in the range of 0.7-7.0% (n = 5) for the same batch, and 1.7-10% (n = 3) for batch to batch. Good linearity for eight pesticides was obtained with coefficient of determination in the range of 0.9942-0.9990. Limit of detections ranged from 0.4 to 1.2 ng/L. Real sample determination showed that four and two pesticides were detected in strawberry and grape, respectively. The results demonstrated that the established method was efficient, sensitive, and convenient for trace determination of pesticides in fruit samples.