Novel Immunosensor Based on Metal Single-Atom Nanozymes with Enhanced Oxidase-Like Activity for Capsaicin Analysis in Spicy Food.

Capsaicin (CAP) is a primary indicator for assessing the level of pungency. Herein, iron-based single-atom nanozymes (SAzymes) (Fe/NC) with exceptional oxidase-like activity were used to construct an immunosensor for CAP analysis. Fe/NC could imitate oxidase actions by transforming O2 to •O2- radicals in the absence of hydrogen peroxide (H2O2), which could avoid complex operations and unstable results. By regulating the Fe atom loads, an optimal Fe0.7/NC atom usage rate could improve the catalytic activity (Michaelis-Menten constant (Km) = 0.09 mM). Fe0.7/NC was integrated with goat antimouse IgG by facile mix incubation to develop a competitive enzyme-linked immunosorbent assay (ELISA). Our Fe0.7/NC immunosensing platform is anticipated to outperform the conventional ELISA in terms of stability and shelf life. The proposed immunosensor provided color responses across 0.01-1000 ng/mL CAP concentrations, with a detection limit of 0.046 ng/mL. Fe/NC may have potential as nanozymes for CAP detection in spicy foods, with promising applications in food biosensing.

Length-controlled hydrophobic CF3-COF as a highly efficient absorbent coating for dual-mode solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons in water samples.

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF3-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF3-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF3-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC-MS/MS), PAHs could be detected in the range of 0.008-0.16 ng mL-1 with a quantitative limit of 0.029-0.47 ng mL-1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF3-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.

Functionalized magnetic metal organic framework nanocomposites for high throughput automation extraction and sensitive detection of antipsychotic drugs in serum samples.

Due to the complexity of biological sample matrix, the automated and high-throughput pretreatment technology is urgently needed for monitoring the antipsychotic drugs for mental patients. In this study, functionalized magnetic zirconium-based organic framework nanocomposites (Fe3O4@SiO2@Zr-MOFs) were successfully designed and synthesized by the layer-by-layer growth. Among them, Fe3O4@SiO2@UiO-67-COOH showed the best adsorption performance, and at the same time it exhibited excellent water dispersibility, high thermal stability, chemical stability and high hydrophobicity. Results of adsorption kinetics, isotherm and FT-IR showed that the adsorption process was dominated by chemical adsorption (hydrogen bond, electrostatic interaction, π-π interaction) and monolayer adsorption. Moreover, the smaller pore size improved the protein exclusion rate which reached 98.9-99.8%. Based on the above result, the synthesized magnetic nanoparticles were introduced to 96-well automatic extractor, antipsychotic drugs in 96 serum samples were automatically extracted within 9 min, which most greatly saved the time and labor costs and avoided artificial errors. By further integrating with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), antipsychotic drugs can be detected in the range of 0.2-3.0 ng mL-1 with a quantitative limit of 0.06-0.9 ng mL-1. The recoveries of antipsychotic drugs and their metabolites in serum ranged from 95.7% to 112.3% within 1.4-6.5% of RSD. These features indicate that the proposed method is promising for high throughput and sensitively monitoring of drugs and other hazardous substances.

Advanced Glycation End Products: A Comprehensive Review of Their Detection and Occurrence in Food.

The Maillard reaction (MR) is a complicated chemical process that has been extensively studied. Harmful chemicals known as advanced glycation end products (AGEs), with complex structures and stable chemical characteristics, are created during the final stage of the MR. AGEs can be formed both during the thermal processing of food and in the human body. The number of AGEs formed in food is much higher compared to endogenous AGEs. A direct connection exists between human health and the build-up of AGEs in the body, which can result in diseases. Therefore, it is essential to understand the content of AGEs in the food we consume. The detection methods of AGEs in food are expounded upon in this review, and the advantages, disadvantages, and application fields of these detection methods are discussed in depth. Additionally, the production of AGEs in food, their content in typical foods, and the mechanisms influencing their formation are summarized. Since AGEs are closely related to the food industry and human health, it is hoped that this review will further the detection of AGEs in food so that their content can be evaluated more conveniently and accurately.

Alanine Substitution to Determine the Effect of LR5 and YR6 Rice Peptide Structure on Antioxidant and Anti-Inflammatory Activity.

The relationship between the structure of peptides LR5 (LHKFR) and YR6 (YGLYPR) and their antioxidant and anti-inflammatory activity remains unclear. Herein, leucine, tyrosine, proline, and phenylalanine at different positions in the peptides were replaced by Alanine (Ala), and two new pentapeptides (AR5 and LAR5) and four hexapeptides (AGR6, YAR6, YLR6, and YGR6) were obtained. The effect of Ala replacement on the hydrophobicity, cytotoxicity, NO inhibition rate, and active oxygen radical scavenging ability of these peptides and their antioxidant and anti-inflammatory abilities were investigated. The results indicated that the hydrophobicity of the peptides was associated with their amino acid composition and their specific sequence. However, hydrophobicity had no significant effect on cytotoxicity. Ala replacement was shown to enhance hydrophobicity and consequently increased the antioxidant and anti-inflammatory activity of the peptides. The molecular docking studies indicated that the amino acid interactions of the peptide with the Keap1 protein influenced the hydrophobicity and thus affected the antioxidant activity of the peptide.

Formation and Characterization of Self-Assembled Rice Protein Hydrolysate Nanoparticles as Soy Isoflavone Delivery Systems.

In this study, soy isoflavones-loaded nanoparticles were prepared using rice proteins (RPs) hydrolyzed by four types of enzyme (alcalase, neutrase, trypsin, and flavorzyme). After optimizing the preparation conditions, the encapsulation efficiency (EE) of the nanoparticles ranged from 61.16% ± 0.92% to 90.65% ± 0.19%. The RPs that were hydrolyzed by flavorzyme with a molecular weight of <5 KDa showed better characters on the formation of nanoparticles, and the formed nanoparticles had the highest EE and loading capacity (9.06%), the smallest particle size (64.77 nm), the lowest polymer dispersity index (0.19), and the lowest zeta potential (-25.64 mV).The results of Fourier transform ion cyclotron resonance, X-ray diffraction, and fluorescence spectroscopy showed that the nanoparticles were successfully encapsulated. The study of interaction showed that the formation of nanoparticles may depend mainly on hydrogen bonds, but other interactions, such as hydrophobic interactions and electrostatic interactions, cannot be ignored. After encapsulation, the pH stability, temperature stability, ionic stability, and oxidation resistance of the nanoparticles were enhanced. Moreover, the in vitro release experiment showed that the encapsulated nanoparticles had a certain protective effect on soybean isoflavones. In summary, rice protein hydrolysates are promising carriers for soybean isoflavones.

An iron-based metal-organic framework as a novel dispersive solid-phase extraction sorbent for the efficient adsorption of tetrabromobisphenol A from environmental water samples.

For environmental safety, it is important to establish a simple, rapid, and sensitive method for emerging pollutants. Here, a dispersive solid-phase extraction (d-SPE) method based on an iron-based metal-organic framework (Fe-MIL-88-NH2) combined with high-performance liquid chromatography (HPLC) was developed for tetrabromobisphenol A (TBBPA) in water samples. Fe-MIL-88-NH2 was synthesized using a solvothermal method and completely characterized. Fe-MIL-88-NH2 had good water stability and gave a maximum adsorption capacity of 40.97 mg g-1 for TBBPA. The adsorption of TBBPA on Fe-MIL-88-NH2 followed Langmuir adsorption models and a pseudo-second-order kinetic model. The bromine ion and the hydroxyl group of TBBPA could form strong hydrogen bond interactions with the amino protons around the cavity of Fe-MIL-88-NH2, which was in accord with the molecular simulation calculations. Furthermore, several important d-SPE parameters were optimized, such as the amount of materials, extraction time, pH, ionic strength, elution solvent type, and volume. The established method showed good linearity in the concentration range of 0.005-100 µg g-1 (r2 ≥ 0.9996). This method's limits of detection (LOD) and quantification (LOQ) were 0.001 µg g-1 and 0.005 µg g-1, respectively. The recoveries in spiked water samples ranged from 87.5% to 104.9%. The proposed method was applied successfully to detect TBBPA in environmental water samples.

Exploration of double Z-type ternary composite long-afterglow/graphitic carbon nitride@metal-organic framework for photocatalytic degradation of methylene blue.

Methylene blue (MB) is a very widely used cationic dye for color cotton and silk products. The harmful MB has a complex aromatic structure that is difficult to be degraded in natural aqueous. In this study for the first time, a novel double Z-type ternary composite long-afterglow/graphitic carbon nitride@metal-organic framework (SrAl2O4:Eu2+,Dy3+/g-C3N4@NH2-UiO-66, SGN) has been synthesized by solvothermal method, and was used as a new photocatalyst for removal of MB. The photocatalytic performance of the composited photocatalyst SGN was largely improved compared to that of the non-composite. After 30 min of photocatalysis, the degradation ratio of SGN was 5.86, 4.04 and 10 times more efficient than that of long-afterglow (SAO), g-C3N4 and NH2-UiO-66, respectively. The high photocatalytic activity of the SGN could be ascribed to the double Z-type electron transfer mechanism. More importantly, due to the luminescence of SAO, the degradation ratio of ternary SGN can reach about 50 % after 5 h in the dark. Superoxide anion (·O2-) was verified to be the main active substance in the photocatalytic process by quenching experiments and electron spin resonance (ESR) spectra analysis. The total organic matter contents (TOC) and partial degradation products were measured, which confirmed that some MB was mineralized into H2O and CO2, and some was degraded into smaller molecules. Moreover, the excellent stability and recyclability of this catalyst were also investigated. Here, a new promising material with high degradation performance for water pollution treatment is presented.

Exploration of long afterglow luminescent materials composited with graphitized carbon nitride for photocatalytic degradation of basic fuchsin.

The frequent exposure of the widely used dye, basic fuchsin (BF), is seriously threatening the health of human central nervous system. Thus, removing the environmental pollution caused by BF is crucial, and photocatalytic technology recently has been used to degrade the pollutions dye. In this study, the binary composite SrAl2O4:Eu2+, Dy3+/g-C3N4 was prepared by high-temperature calcination and then applied in BF photodegradation. The results confirmed that the composite material had lower band gap value (Eg) and stronger visible light absorption ability. The photocatalytic capacity of the new composite materials was enhanced compared to that of the non-composite materials. By using the new binary-composited materials, 80% of BF could be degraded in 10 min, and the degradation ratio reached 100% in 30 min. More importantly, even the light source was removed, the photocatalytic reaction could continue due to the luminescence of SrAl2O4:Eu2+, Dy3+, and the degradation efficiency of BF could finally reach more than 90% within 3 h. By quenching experiments and electron spin resonance (ESR) spectra analysis, superoxide anion (·O2-) was verified to be the main active substance in this reaction process. Moreover, the excellent stability and recyclability of this catalyst was also proved. Furthermore, the new composite materials were utilized to degrade the BF aqueous solution and actual lake water, and the total organic matter contents (TOC) were measured. TOC values in these two systems decreased after photocatalytic reaction, which indicated that this catalyst has a great development prospect in the removal of organic matter in water. Our study confirmed a new kind of material of high performance with great significance for emergency treatment of water pollution in practical applications.

Preparation of high-solubility rice protein using an ultrasound-assisted glycation reaction.

To date, the poor solubility of rice protein (RP) has limited its industrial application in food products. This study aimed to prepare high-solubility RP conjugates using ultrasound-assisted glycation between RP and dextran. The conditions of glycation, treatment at 82 °C for 22 min under 600 W ultrasonic power, were optimized using single-factor experiments and response surface analysis. The solubility of the conjugates reached 90.6 %. Compared with traditional wet-heating glycation, ultrasound-assisted treatment brought more high-molecular-weight components, higher degree of graft, and less contents of arginine and lysine, indicating that ultrasound accelerated the glycation reaction. Ultrasound also resulted in a looser and more flexible structure of RP, manifesting in a 10 % reduction in ß-sheets and 10.6 % increase in random coils of conjugates. The analysis of fluorescence and surface hydrophobicity indicated that ultrasound increased the exposure of hydrophobic residues towards aqueous environment. Besides solubility, the foaming and emulsifying properties of RP were improved through conformational changes. In summary, ultrasound-assisted glycation was found to be an efficient and green method for preparing high-solubility RP conjugates.

Separation of soy isoflavones from soy sauce residue by MIL-100(Fe).

Soy sauce residue (SSR) is a valuable biological resource, which contains soy isoflavones (SIs) with antioxidant activity and can be used to scavenge radicals. Herein, MIL-100(Fe) was synthesized for the extraction of SIs from SSR. Under the optimal adsorption conditions, the adsorption capacity of MIL-100(Fe) for SIs was 51.81 mg/g, which could achieve a purity of 56.17% and a recovery of 93.8%. These results demonstrated MIL-100(Fe) possessed effective properties of adsorption and purification for SIs. The content of SIs in the purified product was 167 times than that of SSR. The purified total SIs had a good antioxidant activity. The established method had a good scavenging ability toward 2, 2-diphenyl-1-picrylhydrazyl, superoxide and hydroxyl radicals, with IC50 values of 0.177, 0.116 and 0.082 mg/mL, respectively. Besides, the ferrous ion chelating potency was better than others, with IC50 values of 0.63 ± 0.0044 mg/mL. The established method was suitable for large-scale separation of purified total SIs and provided a reference for purification of bioactive factors from complex substrates.

Preparation and photocatalytic performance of UIO-66/La-MOF composite.

To improve the photocatalytic degradation efficiency of photocatalytic materials UIO-66 and La-MOFs under visible-light irradiation, a series of photocatalytic materials with La and Zr as metal centers and terephthalic acid (H2BDC) and 2-amino terephthalic acid (H2ATA) as organic ligands were prepared by solvothermal method. The photocatalytic materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and Mott-Schottky test. The photocatalytic degradation performance to Rhodamine B of the catalysts was fully investigated. Results show that the H2ATA series had stronger visible-light absorption capacity and better photocatalytic performance. The 0.35 La/Zr-H2ATA composite showed the best photocatalytic degradation. The quenching experiments confirmed that the active species in the photocatalytic degradation were the holes and superoxide radicals. The possible mechanisms of the carrier migration paths in the energy level matching for La/Zr-H2BDC and La/Zr-H2ATA were also discussed in detail.

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.

In Vitro Anti-Inflammatory Activity of Three Peptides Derived from the Byproduct of Rice Processing.

Inflammation is a contributing factor to the initiation and progression of many diseases, and some food-derived biofunctional peptides show high anti-inflammatory activity. In our previous study, we demonstrated that peptides derived from trypsin hydrolysis of rice protein show good immunological activity. In the present study, proteins of broken rice were extracted and identified by macroporous resin fractionation and liquid chromatography/tandem mass spectrometry (LC-MS/MS). Subsequently, a bioinformatics prediction and in silico simulation approach was used to screen for peptides showing anti-inflammatory activity, including inhibition of the production of nitric oxide and proinflammatory cytokines (interleukin-1ß, interleukin-6, and tumor necrosis factor-α) by lipopolysaccharide-stimulated RAW264.7 mice macrophages. Three peptides (DNIQGITKPAIR, IAFKTNPNSMVSHIAGK, and IGVAMDYSASSKR) that demonstrated the highest binding affinity were synthesized, and their in vitro anti-inflammatory activity was investigated. This is the first study that integrates LC-MS/MS identification and bioinformatics prediction for reporting the anti-inflammatory activity of anti-inflammatory peptides derived from broken rice protein. The study findings revealed that the peptides derived from the byproduct of rice milling could be potentially used as natural anti-inflammatory alternativities.

Photocatalytic degradation of imidacloprid by optimized Bi2WO6/NH2-MIL-88B(Fe) composite under visible light.

Imidacloprid as a widely used neonicotinoid insecticide can cause harmful pesticide residue inevitably. Metal-organic frameworks (MOFs) were innovatively composited to improve the light absorption and degradation performance of Bi2WO6 semiconductor, which expanded the photodegradation application in solving environmental problems. Based on the synergistic effect of Bi2WO6 and NH2-MIL-88B(Fe), a Bi2WO6/NH2-MIL-88B(Fe) (BNM) heterojunction photocatalyst with high-performance of photocatalytic degradation activities was successfully synthesized. The optimized BNM catalyst had a good degradation rate under visible light, which was mainly caused by generation of the active ·OH. Transient photocurrent response and electrochemical impedance tests verified that 1:2 BNM exhibits a highest charge separation and a lowest carrier recombination rate which were favorable to the photocatalytic activity. Cycle experiments show that the composite photocatalyst had good reusability and stability which were very important for potential industry applications.

Peroxidase-mimetic activity of a nanozyme with uniformly dispersed Fe3O4 NPs supported by mesoporous graphitized carbon for determination of glucose.

A Fe3O4/mesoporous graphitized carbon (Fe3O4/m-GC) composite was prepared through a facile calcination method with iron-based metal-organic frameworks (Fe-MOFs) as a sacrificial template. After carbonization, the Fe3O4 nanoparticles were uniformly dispersed in the mesoporous carbon support, resulting in spatial structural stability. The mesoporous carbon support obtained was highly graphitized and exhibited eminent electrical conductivity, which accelerated the electron transfer between the Fe3O4 nanoparticles by Fe(II)/Fe(III) redox cycles and m-GC by C = Csp2/C-Csp3 redox cycles, leading to the excellent peroxidase-mimetic activity of Fe3O4/m-GC. Km values for tetramethylbenzidine (TMB) and H2O2 were 26.8 and 15.8 times lower than that of natural horseradish peroxidase, respectively. Taking advantage of the peroxidase-mimetic activity of Fe3O4/m-GC, a colorimetric assay was fabricated for detecting glucose in the range 0.5 ~ 200 µM, with a limit of detection of 0.24 µM. Fig 1 A Schematic illustration of the preparation process of Fe3O4/m-GC, B schematic illustration of a proposed synergistic catalytic mechanism of TMB oxidation by Fe3O4/m-GC.

New peptides with immunomodulatory activity identified from rice proteins through peptidomic and in silico analysis.

The new food-derived bio-functional peptides are urgently needed globally, but the separation and purification process for obtaining the immunopeptides from food is low efficiency and highly time-consuming. In the present study, rice proteins were extracted and identified by using liquid chromatography/tandem mass spectrometry (LC-MS/MS). Furthermore, a strategy combining immuno-prediction and in silico simulation was used to screen for peptides showing immunomodulatory activity, including inhibition of the release of nitric oxide, tumor necrosis factor-α, and the interleukins IL-6 and IL-1ß in lipopolysaccharide-induced RAW264.7 mouse macrophages. This LC-MS/MS identification and immuno-prediction method may provide insights for the potential identification of more food-derived immunopeptides.

Three-dimensional assembly and disassembly of Fe3O4-decorated porous carbon nanocomposite with enhanced transversal relaxation for magnetic resonance sensing of bisphenol A.

The design and construction of a novel magnetic resonance sensor (MRS) is presented for bisphenol A (BPA) detection. The MRS has been built based on the core component of magnetic Fe3O4 nanoparticles (~ 40 nm), which were uniformly distributed in nanoporous carbon (abbreviated as Fe3O4@NPC). The synthesis was derived from the calcination of the metal organic framework (MOF) precursor of Fe-MIL-101 at high temperature. Fe3O4@NPC was confirmed with enhanced transversal relaxation with r2 value of 118.2 mM-1 s-1, which was around 1.7 times higher than that of the naked Fe3O4 nanoparticle. This enhancement is attributed to the excellent proton transverse relaxation rate of Fe3O4@NPC caused by the reduced self-diffusion coefficient of water molecules in the vicinity of Fe3O4 nanoparticles in the nanoporous carbon. BPA antibody (Ab) and antigen (Ag)-ovalbumin (OVA) were immobilized onto the Fe3O4@NPC to form Ab-Fe3O4@NPC and Ag-Fe3O4@NPC, respectively. These two composites can cause the three-dimensional assembly of Fe3O4@NPC via immunological recognition. The presence of BPA can compete with antigen-OVA to combine with Ab-Fe3O4@NPC, thereby breaking the assembly process (disassembly). The difference in the change of the T2 value before and after adding BPA can thus be used to monitor BPA. The proposed MRS not only revealed a wide linear range of BPA concentration from 0.05 to 50 ng mL-1 with an extremely low detection limit of 0.012 ng mL-1 (S/N = 3), but also displayed high selectivity towards matrix interferences. The recoveries of BPA ranged from 95.6 to 108.4% for spiked tea π, and 93.4 to 104.7% for spiked canned oranges samples, respectively, and the RSD (n = 3) was less than 4.4% for 3 successive assays. The versatility of Fe3O4@NPC with customized relaxation responses provides the possibility for the adaptation of magnetic resonance platforms for food safety development. The magnetic Fe3O4 nanoparticles are uniformly dispersed in the nanoporous carbon (Fe3O4@NPC), which derived from the calcinating of the metal organic framework (MOF) precursor of Fe-MIL-101. And the magnetic Fe3O4@NPCs are adopted for the construction of magnetic resonance sensor (MRS) for bisphenol A (BPA) detection.

A nanozyme-linked immunosorbent assay based on metal-organic frameworks (MOFs) for sensitive detection of aflatoxin B1.

In order to avoid the occurrence of false positives and false negatives caused by conventional enzyme-linked immunosorbent assay (ELISA), we established a novel indirect competitive MOF-linked immunosorbent assay (MOFLISA) method for the high throughput and high sensitive detection of aflatoxin B1. This method replaces the natural enzyme with functional MOFs to catalyze a chromogenic system. As a result, the limit of detection (LOD) of the MOFLISA method was 0.009 ng·mL-1 with a linear working range from 0.01 to 20 ng·mL-1. The developed MOFLISA method for AFB1 has a 20-fold improved LOD value compared with the conventional ELISA. The recoveries and relative standard deviations (RSD) ranged from 86.41 to 99.74% and 2.38-9.04%, respectively. The results demonstrate that the recovery rate and accuracy of this detection method is better than that of conventional ELISA, reducing risks offalsepositive andfalsenegativeresults.