Complex insoluble dietary fiber alleviates obesity and liver steatosis, and modulates the gut microbiota in C57BL/6J mice fed a high-fat diet.

BACKGROUND: Obesity has been demonstrated as a risk factor that seriously affects health. Insoluble dietary fiber (IDF), as a major component of dietary fiber, has positive effects on obesity, inflammation and diabetes. RESULTS: In this study, complex IDF was prepared using 50% enoki mushroom IDF, 40% carrot IDF, and 10% oat IDF. The effects and potential mechanism of complex IDF on obesity were investigated in C57BL/6 mice fed a high-fat diet. The results showed that feeding diets containing 5% complex IDF for 8 weeks significantly reduced mouse body weight, epididymal lipid index, and ectopic fat deposition, and improved mouse liver lipotoxicity (reduced serum levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase), fatty liver, and short-chain fatty acid composition. High-throughput sequencing of 16S rRNA and analysis of fecal metabolomics showed that the intervention with complex IDF reversed the high-fat-diet-induced dysbiosis of gut microbiota, which is associated with obesity and intestinal inflammation, and affected metabolic pathways, such as primary bile acid biosynthesis, related to fat digestion and absorption. CONCLUSION: Composite IDF intervention can effectively inhibit high-fat-diet-induced obesity and related symptoms and affect the gut microbiota and related metabolic pathways in obesity. Complex IDF has potential value in the prevention of obesity and metabolic syndrome. © 2024 Society of Chemical Industry.

Phase Transition Behaviors of Poly(N-isopropylacrylamide) Nanogels with Different Compositions Induced by (-)-Epigallocatechin-3-gallate and Ethyl Gallate.

Phase transition behaviors of poly(N-isopropylacrylamide) nanogels with different compositions induced by (-)-epigallocatechin-3-gallate (EGCG) and ethyl gallate (EG) has been investigated systematically. Monodisperse poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) (P(NIPAM-co-NMAM)) and poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)) nanogels with different feeding monomer ratios were prepared by emulsion polymerization. P(NIPAM-co-NMAM) nanogels exhibit rapid isothermal phase transition behavior in EGCG solutions with low concentration (10-3 mol/L) in less than 10 minutes. The thermosensitive phase transition behaviors of nanogels are affected not only by the copolymerized monomers but also by the concentrations of EGCG and EG in aqueous solutions. Nanogels remain in a shrunken state and do not exhibit thermosensitive phase transition behaviors in EGCG solutions (≥5 mmol/L), whereas they display thermo-responsive phase transition behaviors in EG solutions. The volume phase transition temperature (VPTT) shifts to lower temperatures with increasing EG concentration. The diameters of P(NIPAM-co-NMAM) nanogels decrease with increasing EG concentration at temperatures between 29 and 33 °C. In contrast, the diameters of P(NIPAM-co-HEMA) nanogels increase with increasing EGCG concentration at temperatures between 37 and 45 °C. The results demonstrate the potential of nanogels for simple detection of EG and EGCG concentrations in aqueous solutions over a wide temperature range, and EGCG can serve as a signal for the burst-release of drugs from the P(NIPAM-co-NMAM)-based carriers at physiological temperature.

What role does the seed coat play during symbiotic seed germination in orchids: an experimental approach with Dendrobium officinale.

BACKGROUND: Orchids require specific mycorrhizal associations for seed germination. During symbiotic germination, the seed coat is the first point of fungal attachment, and whether the seed coat plays a role in the identification of compatible and incompatible fungi is unclear. Here, we compared the effects of compatible and incompatible fungi on seed germination, protocorm formation, seedling development, and colonization patterns in Dendrobium officinale; additionally, two experimental approaches, seeds pretreated with NaClO to change the permeability of the seed coat and fungi incubated with in vitro-produced protocorms, were used to assess the role of seed coat played during symbiotic seed germination. RESULTS: The two compatible fungi, Tulasnella sp. TPYD-2 and Serendipita indica PI could quickly promote D. officinale seed germination to the seedling stage. Sixty-two days after incubation, 67.8 ± 5.23% of seeds developed into seedlings with two leaves in the PI treatment, which was significantly higher than that in the TPYD-2 treatment (37.1 ± 3.55%), and massive pelotons formed inside the basal cells of the protocorm or seedlings in both compatible fungi treatments. In contrast, the incompatible fungus Tulasnella sp. FDd1 did not promote seed germination up to seedlings at 62 days after incubation, and only a few pelotons were occasionally observed inside the protocorms. NaClO seed pretreatment improved seed germination under all three fungal treatments but did not improve seed colonization or promote seedling formation by incompatible fungi. Without the seed coat barrier, the colonization of in vitro-produced protocorms by TPYD-2 and PI was slowed, postponing protocorm development and seedling formation compared to those in intact seeds incubated with the same fungi. Moreover, the incompatible fungus FDd1 was still unable to colonize in vitro-produced protocorms and promote seedling formation. CONCLUSIONS: Compatible fungi could quickly promote seed germination up to the seedling stage accompanied by hyphal colonization of seeds and formation of many pelotons inside cells, while incompatible fungi could not continuously colonize seeds and form enough protocorms to support D. officinale seedling development. The improvement of seed germination by seed pretreatment may result from improving the seed coat hydrophilicity and permeability, but seed pretreatment cannot change the compatibility of a fungus with an orchid. Without a seed coat, the incompatible fungus FDd1 still cannot colonize in vitro-produced protocorms or support seedling development. These results suggest that seed coats are not involved in symbiotic germination in D. officinale.

A novel colorimetric aptasensor for sensitive tetracycline detection based on the peroxidase-like activity of Fe3O4@Cu nanoparticles and "sandwich" oligonucleotide hybridization.

A novel colorimetric aptasensor has been developed for highly sensitive tetracycline (TC) detection based on the peroxidase-like activity of Fe3O4@Cu nanoparticles and "sandwich" oligonucleotide hybridization. The Fe3O4@Cu nanoparticles with high peroxidase-like activity were successfully synthesized under mild conditions. Then, a "sandwich" oligonucleotide hybridization probe (a short amino-modified complementary sequence of a portion of the TC aptamer (cDNA1), TC aptamers, and a long complementary to 5' terminal TC aptamer sequence (cDNA2)) was created in 96-wells plates via DNA hybridization in the absence of TC from the detection system. The unique "sandwich" oligonucleotide hybridization probe adsorbed large numbers of Fe3O4@Cu nanozymes while further enhancing its peroxidase-like activity. Based on the 3,3',5,5'-tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) reporting system, the blue color of the solution decreased linearly with the increase of TC concentration, ranging from 10-3 to 103 µg/L with an ultralow limit of detection (LOD) of 0.91 ng/L (2 pM). The proposed method was successfully applied to detect TC in spiked milk samples, with recoveries of 81.8 to 112%, demonstrating the excellent potential for highly sensitive TC detection in milk.

A Dual-Mode Method Based on Aptamer Recognition and Time-Resolved Fluorescence Resonance Energy Transfer for Histamine Detection in Fish.

Histamine produced via the secretion of histidine decarboxylase by the bacteria in fish muscles is a toxic biogenic amine and of significant concern in food hygiene, since a high intake can cause poisoning in humans. This study proposed a fluorometric and colorimetric dual-mode specific method for the detection of histamine in fish, based on the fluorescence labeling of a histamine specific aptamer via the quenching and optical properties of gold nanoparticles (AuNPs). Due to the fluorescence resonance energy transfer phenomenon caused by the proximity of AuNPs and NaYF4:Ce/Tb, resulting in the quenching of the fluorescence signal in the detection system, the presence of histamine will compete with AuNPs to capture the aptamer and release it from the AuNP surface, inducing fluorescence recovery. Meanwhile, the combined detection of the two modes showed good linearity with histamine concentration, the linear detection range of the dual-mode synthesis was 0.2-1.0 µmol/L, with a detection limit of 4.57 nmol/L. Thus, this method has good selectivity and was successfully applied to the detection of histamine in fish foodstuffs with the recoveries of 83.39~102.027% and 82.19~105.94% for Trichiurus haumela and Thamnaconus septentrionalis, respectively. In addition, this method was shown to be simple, rapid, and easy to conduct. Through the mutual verification and combined use of the two modes, a highly sensitive, rapid, and accurate dual-mode detection method for the analysis of histamine content in food was established, thereby providing a reference for the monitoring of food freshness.

Improving the detection limit of Salmonella colorimetry using long ssDNA of asymmetric-PCR and non-functionalized AuNPs.

A colorimetric sensor based on gold nanoparticles (AuNPs) and single-stranded DNA (ssDNA) is a simple and rapid method for detecting foodborne pathogens. However, the colorimetric method employed in previous studies involved short ssDNA (<100 nucleotides), including the aptamer and PCR products, resulting in the high detection limit of this technique. In this study, a colorimetric sensor was developed based on long ssDNA of asymmetric PCR (aPCR) and non-functionalized AuNPs for detecting Salmonella Typhimurium (S. Typhimurium). In the presence of S. Typhimurium, the long ssDNA (547 nt) amplified by aPCR-protected AuNPs from NaCl-induced aggregation, while the solution retained a red color. After optimizing parameters, the limit of detection (LOD) of the colorimetric sensor was 2.56 CFU/mL with high specificity. Recovery studies showed its feasibility for detecting S. Typhimurium (102 CFU/mL, 104 CFU/mL, and 106 CFU/mL) in spiked lettuce samples. This colorimetric sensor provides new opportunities for the highly sensitive detection of bacteria in real food samples.

Colorimetric method for Salmonella spp. detection based on peroxidase-like activity of Cu(II)-rGO nanoparticles and PCR.

Development of a rapid and sensitive method for Salmonella spp. detection is of great importance for ensuring food product safety due to its low infective dose. In this study, a colorimetric method based on the peroxidase-like activity of Cu(II)-modified reduced graphene oxide nanoparticles (Cu2+-rGO NPs) and PCR was successfully developed to detect Salmonella spp. in milk. Under optimal conditions, the developed colorimetric method exhibited high sensitivity and strong specificity for Salmonella spp. detection. The limit of detection was 0.51 CFU/mL with a linear range from 1.93 × 101 to 1.93 × 105 CFU/mL. A specificity study demonstrated that this method can specifically distinguish Salmonella typhimurium and Salmonella enteritidis from other foodborne pathogens. The application of the proposed method for milk sample detection was also validated, and the recovery rates of S. typhimurium in spiked milk sample ranged from 102.84% to 112.25%. This colorimetric sensor exhibits enormous potential for highly sensitive detection of bacteria in milk sample.

A time-resolved luminescence aptasensor of ofloxacin based on rolling circle amplification and magnetic separation.

A novel sensitive, competitive, and time-resolved luminescence sensor for the detection of ofloxacin (OFL) was developed in this study. The sensor used OFL-specific aptamer as a recognition molecule and rolling circle amplification (RCA) as a signal amplification tool. In this way, the time-resolved luminescence can not only avoid background noise from sample, but also provide robust luminescence for detection. Besides, the separation and enrichment of target veterinary drug can be conducted assisted by magnetic treatment. Under optimal conditions, the logarithmic correlation between the concentration of OFL and the luminescence intensity was found to be linear in the range of 5 × 10-11-5 × 10-8 mol L-1 (R2 = 0.9988), with a detection limit (LOD) of 32.1 pmol L-1. Furthermore, this method was applied to the determination of OFL in chicken and pork samples, exhibiting good recovery (72.5-100%) and repeatability (RSD < 10.0%). These results confirm that this novel established method has good application potential for the detection of OFL in food samples.

Changes in the properties of Radix Aconiti Lateralis Preparata (Fuzi, processed aconite roots) starch during processing.

Radix Aconiti Lateralis Preparata (Fuzi) is an important, toxic traditional Chinese medicine that has been widely used in clinical practice. Due to the toxicity of its raw materials, it needs to be processed before application. The changes in the physicochemical properties of Fuzi starch during processing were evaluated by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The results showed the following: morphological properties changed from spherical to irregular and polygonal particles, while the particle size increased significantly; amylose content and solubility decreased significantly; swelling power and water-binding capacity increased significantly; the X-ray diffraction peak disappeared, and the crystallinity decreased; and the gelatinization temperature and enthalpy decreased significantly. The properties of Fuzi starch were similar to those of pregelatinized starch. These results indicated that Fuzi starch undergone repeated processes of gelatinization and aging, which destroyed the original crystal structure of the starch.

Selection and characterization, application of a DNA aptamer targeted to Streptococcus pyogenes in cooked chicken.

An aptamer against Streptococcus pyogenes was selected and identified, and a fluorescent method based on the reported aptamer was established to detect S. pyogenes in the cooked chicken. Through a twelve rounds of whole-bacterium SELEX (systematic evolution of ligands by exponential enrichment) selection in vitro, a set of aptamers binding to the whole cell of S. pyogenes were generated, harvesting a low-level dissociation constant (Kd) value of 44 ±â€¯5 nmol L-1 of aptamer S-12. Aptamer-based quantification of S. pyogenes in the cooked chicken sample was implemented in a fluorescence resonance energy transfer-based assay by using graphene oxide, resulting in a limit of detection of 70 cfu mL-1. The selected aptamer showed affinity and selectivity recognizing S. pyogenes; besides, more biosensors based on the selected aptamer as a molecular recognition element could be developed in the innovative determinations of S. pyogenes.

Identification and characterization of a novel carboxylesterase from Phaseolus vulgaris for detection of organophosphate and carbamates pesticides.

BACKGROUND: Organophosphate and carbamate pesticide residues in food and the environment pose a great threat to human health and have made the easy and rapid detection of these pesticide residues an important task. Discovering new enzyme sources from plants can help reduce the cost of large-scale applications of rapid pesticide detection via enzyme inhibition. RESULTS: Plant esterase from kidney beans was purified. Kidney bean esterase is identified as a carboxylesterase by substrate and inhibitor specificity tests and mass spectrometry identification. The kidney bean esterase demonstrates optimal catalytic activity at 40 °C, pH 6.5 and an enzyme concentration of 0.30 µg mL-1 . The kidney bean esterase can be inhibited by organophosphate and carbamate pesticides, which can be substituted for acetylcholinesterase. The limit of detection of the purified kidney bean esterase was two- to 20-fold higher than that of the crude one. The method detection limit meets the detection requirement for the maximum residue limits (MRL) in actual samples. CONCLUSION: The findings of the present study provide a new source of enzymes for pesticides detection by enzyme inhibition. © 2018 Society of Chemical Industry.

Oxidation pretreatment by calcium hypochlorite to improve the sensitivity of enzyme inhibition-based detection of organophosphorus pesticides.

BACKGROUND: Enzyme inhibition-based detection is the most widely used method for rapid detection of organophosphorus pesticides (OPs) in food and agricultural products. However, the accuracy of the method is negatively affected by low inhibitory activities of OPs with PS moiety on acetylcholinesterase. RESULTS: We demonstrated that oxidation pretreatments with bromine, hydrogen peroxide, or calcium hypochlorite significantly enhanced the enzyme inhibitory activities of these OPs. Especially, calcium hypochlorite (0.05%) pretreatment converted the PS moiety in OPs to PO and produced the most potent and steady inhibitory effect on the enzyme. This, in turn, resulted in a dramatic increase in the sensitivity of enzyme inhibition-based detection of these OPs by as much as 2 to 7 orders of magnitude. Importantly, this enhanced detection of OPs was validated in various vegetable samples. CONCLUSION: Our findings provide a solid basis to use calcium hypochlorite pretreatment for the improved detection of OPs by the enzyme inhibition-based method. © 2017 Society of Chemical Industry.

Successful expression of the Bordetella petrii nitrile hydratase activator P14K and the unnecessary role of Ser115.

BACKGROUND: The activator P14K is necessary for the activation of nitrile hydratase (NHase). However, it is hard to be expressed heterogeneously. Although an N-terminal strep tagged P14K could be successfully expressed from Pseudomonas putida, various strategies for the over-expression of P14K are needed to facilitate further application of NHase. RESULTS: P14K was successfully expressed through fusing a his tag (his-P14K), and was over-expressed through fusing a gst tag (gst-P14K) at its N-terminus in the NHase of Bordetella petrii DSM 12804. The stability of gst-P14K was demonstrated to be higher than that of the his-P14K. In addition, the Ser115 in the characteristic motif CXLC-Ser115-C of the active center of NHase was found to be unnecessary for NHase maturation. CONCLUSIONS: Our results are not only useful for the NHase activator expression and the understanding of the role of Ser115 during NHase activation, but also helpful for other proteins with difficulty in heterologous expression.

Oxidation of Chlorpromazine by Lipoxygenase Immobilized on Magnetic Fe3O4 Nanoparticles.

In this work, soybean lipoxygenase enzyme was immobilized on the magnetic Fe3O4 nanoparticles to oxidate chlorpromazine (CPZ). The physicochemical properties of the nanoparticles were characterized with transmission electronic microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA), and the magnetic properties were detected by a vibrating sample magnetometer (VSM). The TEM images indicated the surface and the size of the immobilized enzyme were much rougher and thicker than those of the naked particles. The analyses of XRD patterns showed that the structure of the magnetic nanoparticles had no significant change while the nanoparticles also exhibited higher superparamagnetism at room temperature. Compared to free enzyme or the enzyme immobilized with other methods, the optimal pH, temperature and H2O2 concentration for the activity of immobilized enzyme did not have great changes, but the immobilized enzyme was more stable and less sensitive to the change of the influence factors than free counterpart. The immobilized enzyme could be recovered easily by magnetic separation and could be reused for many times in the process of CPZ oxidation. The results obtained by simulating the model of Michaelis-Menten indicated that the reaction of CPZ oxidation followed Michaelis-Menten kinetics and the enzyme still retained its affinity for CPZ while the enzyme was immobilized.

An integrated molecular docking and rescoring method for predicting the sensitivity spectrum of various serine hydrolases to organophosphorus pesticides.

BACKGROUND: The enzymatic chemistry method is currently the most widely used method for the rapid detection of organophosphorus (OP) pesticides, but the enzymes used, such as cholinesterases, lack sufficient sensitivity to detect low concentrations of OP pesticides present in given samples. Serine hydrolase is considered an ideal enzyme source in seeking high-sensitivity enzymes used for OP pesticide detection. However, it is difficult to systematically evaluate sensitivities of various serine hydrolases to OP pesticides by in vitro experiments. This study aimed to establish an in silico method to predict the sensitivity spectrum of various serine hydrolases to OP pesticides. RESULTS: A serine hydrolase database containing 219 representative serine hydrolases was constructed. Based on this database, an integrated molecular docking and rescoring method was established, in which the AutoDock Vina program was used to produce the binding poses of OP pesticides to various serine hydrolases and the ID-Score method developed recently by us was adopted as a rescoring method to predict their binding affinities. In retrospective case studies, this method showed good performance in predicting the sensitivities of known serine hydrolases to two OP pesticides: paraoxon and diisopropyl fluorophosphate. The sensitivity spectrum of the 219 collected serine hydrolases to 37 commonly used OP pesticides was finally obtained using this method. CONCLUSION: Overall, this study presented a promising in silico tool to predict the sensitivity spectrum of various serine hydrolases to OP pesticides, which will help in finding high-sensitivity serine hydrolases for OP pesticide detection.

[Preliminary processing, processing and usage of Dendrobii Caulis in history].

On account of the dense cuticles of the fresh stem and the light, hard and pliable texture of the dried stem, Dendrobii Caulis is difficult to dry or pulverize. So, it is very important to the ancient doctors that Dendrobii Caulis should be properly treated and applied to keep or evoke its medicinal effects. The current textual research results about the preliminary processing, processing and usage methods of Dendrobii Caulis showed that: (1) In history the clinical use of fresh or processed Dendrobii Caulis as teas and tinctures were very common. (2) Its roots and rhizomes would be removed before using. (3) Some ancillary approaches were applied to shorten drying times, such as rinsing with boiling mulberry-ash soup, washing or soaking with liquor, mixing with rice pulp and then basking, etc. (4) According to the ancients knowledge, the sufficient pulverization, by means of slicing, rasping, hitting or pestling techniques, was necessary for Dendrobii Caulis to take its effects. (5) The heat processing methods for Dendrobii Caulis included stir-baking, stir-frying, steaming, decocting and stewing techniques, usually with liquor as an auxiliary material. Among above mentioned, steaming by pretreating with liquor was most commonly used, and this scheme was colorfully drawn in Bu Yi Lei Gong Pao Zhi Bian Lan (Ming Dynasty, 1591 CE) ; moreover, decocting in advance or long-time simmering so as to prepare paste products were recommended in the Qing Dynasty. (6) Some different processing programs involving stir-baking with grit, air-tightly baking with ondol (Kangs), fumigating with sulfur, which appeared in modern times and brought attractive outward appearance of the drug, went against ancients original intentions of ensuring drug efficacy.

Universal organophosphate pesticides detection by peptide based fluorescent probes.

In practical applications, the rapid and efficient detection of universal organophosphorus pesticides (OPs) can assist inspectors in quickly identifying the presence of OPs in samples. However, this presents a challenge for most well-established methods, typically designed to detect only a specific type of organophosphorus molecule at a time. In this proof-of-concept study, we draw inspiration from the structural similarities among OPs to develop innovative peptide-based fluorescence probes for the first time, which could efficiently detect a broad range of OPs within a mere 3 min. Analysis of fluorescence curve fitting reveals a clear linear correlation between the fluorescent intensity of the peptide probes and the concentration of OPs. Additionally, the selectivity analysis indicates that these peptide fluorescent probes exhibit an excellent response to various OPs while maintaining sufficient selectivity for detecting other pesticide types. Accurate sample analysis has also highlighted the potential of these peptide probes as practical tools for the rapid detection of OPs in actual vegetable samples. In summary, this proof-of-concept study presents an innovative approach to designing and developing ultrafast, universally peptide-based OP probes. These custom-designed peptide probes may facilitate rapid sample screening and offer initial quantification for OPs, potentially saving valuable time and effort in practical OP detection.

Exploring organophosphate ester contamination and distribution in food: A meta-analysis.

This study examines the food safety risk of organophosphate esters (OPEs) by analyzing data from 23 studies with 14,915 data points. We found EDP contamination highest in cereals, dairy, and meats, and TEHP most prevalent in vegetables and fruits, with contamination levels reaching 4.54 ng/g and 1.46 ng/g, respectively. Food processing influences OPE contamination through complex and multifaceted, akin to a "double-edged sword.", as meta-analysis and Principal Component Analysis (PCA) revealed. Estimated Dietary Intakes (EDI) identified vegetables and cereals as primary OPE sources, contributing 33.3% and 23.8% of total intake, with EDI values of 44.74 ng/kg bw/day and 32.25 ng/kg bw/day, respectively. Current exposure levels are within U.S. EPA safety thresholds (HQ < < 1), but the heightened risk to infants and children necessitates revising safety standards and ongoing monitoring.

Facile fabrication of a novel, photodetachable salecan-based hydrogel dressing with self-healing, injectable, and antibacterial properties based on metal coordination.

Achieving the controllable detachment of polysaccharide-based wound dressings is challenging. In this study, a novel, photodetachable salecan-based hydrogel dressing with injectable, self-healing, antibacterial, and wound healing properties was developed using a green and facile approach. A salecan hydrogel with a uniform porous structure and water content of 90.4 % was prepared by simply mixing salecan and an Fe3+-citric acid complexing solution in an acidic D-(+)-glucono-1,5-lactone environment. Metal coordinate interactions were formed between the released Fe3+ ions and carboxyl groups on the salecan polysaccharide, inducing homogeneous gelation. Benefiting from this dynamic and reversible crosslinking, the salecan hydrogel exhibited self-healing and injectable behavior, facilitating the formation of the desired shapes in situ. The exposure of Fe3+-citric acid to UV light (365 nm) resulted in the reduction of Fe3+ to Fe2+ through photochemical reactions, enabling phototriggered detachment. Moreover, the hydrogel exhibited excellent biocompatibility and satisfactory antibacterial efficacy against Escherichia coli and Staphylococcus aureus of 72.5 % and 85.3 %, respectively. The adhesive strength of the salecan hydrogel to porcine skin was 1.06 ± 0.12 kPa. In vivo wound healing experiments further highlighted the advantages of the prepared hydrogel in alleviating the degree of wound inflammation and promoting tissue regeneration within 12 days.

Mechanistic investigation and dual-mode colorimetric-chemiluminescent detection of glyphosate based on the specific inhibition of Fe3O4@Cu nanozyme peroxidase-like activity.

In this study, a dual-mode colorimetric/CL nanosensor was developed for glyphosate detection based on the specific inhibition of Fe3O4@Cu peroxidase-like activity. Synthesized Fe3O4@Cu exhibited high levels of peroxidase-like activity that triggered the oxidation of luminol/3,3',5,5'-tetramethyl benzidine dihydrochloride (TMB) to excited-state 3-aminophthalic acid/blue oxTMB, thereby delivering a CL signal/visible colorimetric signal, however, the presence of glyphosate inhibited this activity, resulting in a decrease in signal strength. In-depth investigation revealed that this inhibitory mechanism occurs via two pathways: one in which glyphosate chelates with Fe(III)/Cu(II) and occupy the catalytical active sites of Fe3O4@Cu, thereby decreasing the generation of OH, and another in which glyphosate competes with TMB to consume generated OH, thus reducing the oxidation of TMB. This mechanism formed the basis of our novel dual-mode colorimetric/CL glyphosate nanosensor, which achieved limits of detection (LODs) of 0.086 µg/mL and 0.019 µg/mL in tests, thus demonstrating its significant potential for on-site glyphosate monitoring.