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The ratiometric fluorescent probe UiO-OH@Tb, a zirconium-based MOF functionalized with Tb3+, was synthesized using a hydrothermal method. This probe employs the fluorescence resonance energy transfer (FRET) mechanism between Tb3+ and malachite green (MG) for the double-inverse signal ratiometric fluorescence detection of MG. The probe's color shifts from lime green to blue with an increasing concentration of MG. In contrast, the monometallic MOFs' (UiO-OH) probe shows only blue fluorescence quenching due to the inner filter effect (IFE) after interacting with MG. Additionally, the composite fluorescent probe (UiO-OH@Tb) exhibits superior sensitivity, with a detection limit (LOD) of 0.19 µM, which is significantly lower than that of the monometallic MOFs (25 µM). Moreover, the content of MG can be detected on-site (LOD = 0.94 µM) using the RGB function of smartphones. Hence, the UiO-OH@Tb probe is proven to be an ideal material for MG detection, demonstrating significant practical value in real-world applications.

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BACKGROUND: Aptamers are screened via the systematic evolution of ligands by exponential enrichment (SELEX) and are widely used in molecular diagnostics and targeted therapies. The development of efficient and convenient SELEX technology has facilitated rapid access to high-performance aptamers, thereby advancing the aptamer industry. Graphene oxide (GO) serves as an immobilization matrix for libraries in GO-SELEX, making it suitable for screening aptamers against diverse targets. RESULTS: This review summarizes the detailed steps involved in GO-SELEX, including monitoring methods, various sublibrary acquisition methods, and practical applications from its inception to the present day. In addition, the potential of GO-SELEX in the development of broad-spectrum aptamers is explored, and its current limitations for future development are emphasized. This review effectively promotes the application of the GO-SELEX technique by providing valuable insights and assisting researchers interested in conducting related studies. SIGNIFICANCE AND NOVELTY: To date, no review on the topic of GO-SELEX has been published, making it challenging for researchers to initiate studies in this area. We believe that this review will broaden the SELEX options available to researchers, ensuring that they can meet the growing demand for molecular probes in the scientific domain.

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This study aimed to develop a novel fluorescent aptasensor for the quantitative detection of zearalenone (ZEN), addressing the limitations of conventional detection techniques in terms of speed, sensitivity, and ease of use. Nitrogen-doped carbon dots (N-CDs) were synthesized via the hydrothermal method, resulting in spherical particles with a diameter of 3.25 nm. These N-CDs demonstrated high water solubility and emitted a bright blue light at 440 nm when excited at 355 nm. The fluorescence of N-CDs was quenched by dispersed gold nanoparticles (AuNPs) through the inner filter effect, while aggregated AuNPs induced by NaCl did not affect the fluorescence of N-CDs. The aptamer could protect AuNPs from NaCl-induced aggregation, but the presence of ZEN weakened this protective effect. Based on this principle, optimal conditions for ZEN detection included 57 mM NaCl, 12.5 nM aptamer concentration, incubation of AuNPs with NaCl for 15 min in Tris-EDTA(TE) buffer, and incubation of aptamer with ZEN and NaCl for 30 min. Under these optimized conditions, the "signal-on" fluorescent aptasensor for ZEN detection showed a linear range of 0.25 to 200 ng/mL with a low detection limit of 0.0875 ng/mL. Furthermore, the developed aptasensor exhibited excellent specificity and could rapidly detect ZEN in corn flour samples or corn oil, achieving satisfactory recovery rates ranging from 84.7% to 108.6%. Therefore, this study presents an economical, convenient, sensitive, and rapid method for accurately quantifying ZEN in cereal products.

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Similar to other RNA viruses, grass carp reovirus, the causative agent of the hemorrhagic disease, replicates in cytoplasmic viral inclusion bodies (VIBs), orchestrated by host proteins and lipids. The host pathways that facilitate the formation and function of GCRV VIBs are poorly understood. This work demonstrates that GCRV manipulates grass carp oxysterol binding protein 1 (named as gcOSBP1) and vesicle-associated membrane protein-associated protein A/B (named as gcVAP-A/B), 3 components of cholesterol transport pathway, to generate VIBs. By siRNA-mediated knockdown, we demonstrate that gcOSBP1 is an essential host factor for GCRV replication. We reveal that the nonstructural proteins NS80 and NS38 of GCRV interact with gcOSBP1, and that the gcOSBP1 is recruited by NS38 and NS80 for promoting the generation of VIBs. gcOSBP1 increases the expression of gcVAP-A/B and promotes the accumulation of intracellular cholesterol. gcOSBP1 also interacts with gcVAP-A/B for forming gcOSBP1-gcVAP-A/B complexes, which contribute to enhance the accumulation of intracellular cholesterol and gcOSBP1-mediated generation of VIBs. Inhibiting cholesterol accumulation by lovastatin can completely abolish the effects of gcOSBP1 and/or gcVAP-A/B in promoting GCRV infection, suggesting that cholesterol accumulation is vital for gcOSBP1- and/or gcVAP-A/B-mediated GCRV replication. Thus, our results, which highlight that gcOSBP1 functions in the replication of GCRV via its interaction with essential viral proteins for forming VIBs and with host gcVAP-A/B, provide key molecular targets for obtaining anti-hemorrhagic disease grass carp via gene editing technology.

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The ecological environment of the middle Yellow River is highly vulnerable. Conducting a scientific assessment of landscape pattern vulnerability holds great significance, as it serves as the basis for the rational construction of the ecological environment in this area. Based on five periods of land use data from the middle Yellow River from 1990 to 2018, the landscape pattern vulnerability index was employed to analyze the spatio-temporal evolution of the landscape pattern vulnerability. Furthermore, the influencing factors for landscape pattern vulnerability in different natural geomorphological divisions were explored using an optimal parameters-based geographical detector model. The results showed that:① From 1990 to 2018, cultivated land (which accounted for 36.96 % to 39.97 % of the area) remained the predominant landscape in the middle Yellow River. Among all landscape types, cultivated land and construction land exhibited the most significant changes. The area of cultivated land decreased by 10 185.00 km2, whereas the area of construction land increased by 7 678.46 km2. ② From 1990 to 2018, the landscape pattern was dominated by low and medium vulnerability and accounted for 70 %-80 % of the total area. The high and higher vulnerability areas were concentrated in the loess hilly and gully region, whereas the lower vulnerability area was concentrated in the valley plain and the earth-rock mountain regions. During this period, landscape pattern vulnerability underwent an incipient decrease, followed by a subsequent increase. From 1990 to 2000 and from 2000 to 2005, the changes in the level of landscape pattern vulnerability were dominated by a "reduction in the degree of vulnerability". However, from 2005 to 2010 and from 2010 to 2018, it was mainly an "increase in the degree of vulnerability". ③ Annual precipitation and NDVI were the main factors influencing the vulnerability of landscape patterns, whereas the influencing factors varied across different natural geomorphological divisions:the loess hilly and gully region and the earth-rock mountain region were dominated by natural factors, with annual precipitation and DEM being the dominant factors, respectively; the loess plateau tableland-gully region, valley plain region, and sandy land and desert region were dominated by human factors, with population density, degree of land use, and distance from roads being the dominant factors, respectively. The interaction results of any two influencing factors were manifested as two-factor enhancement or nonlinear enhancement. Risk detection revealed that high vulnerability areas of landscape patterns in different natural geomorphological divisions were distributed over distinct ranges of their corresponding dominant factors. Therefore, in the practices of ecological management in the middle Yellow River, appropriate management strategies should be implemented based on the vulnerability characteristics of different natural landforms, to further improve the ecological management level of the watershed.

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The detection of biomarkers is of great significance for medical diagnosis, food safety, environmental monitoring, and agriculture. However, bio-detection technology at present often necessitates complex instruments, expensive reagents, specialized expertise, and prolonged procedures, making it challenging to fulfill the demand for rapid, sensitive, user-friendly, and economical testing. In contrast, lateral flow strip (LFS) technology offers simple, fast, and visually accessible detection modality, allowing real-time analysis of clinical specimens, thus finding widespread utility across various domains. Within the realm of LFS, the application of aptamers as molecular recognition probes presents distinct advantages over antibodies, including cost-effectiveness, smaller size, ease of synthesis, and chemical stability. In recent years, aptamer-based LFS has found extensive application in qualitative, semi-quantitative, and quantitative detection across food safety, environmental surveillance, clinical diagnostics, and other domains. This review provided a concise overview of different aptamer screening methodologies, selection strategies, underlying principles, and procedural, elucidating their respective advantages, limitations, and applications. Additionally, we summarized recent strategies and mechanisms for aptamer-based LFS, such as the sandwich and competitive methods. Furthermore, we classified LFSs constructed based on aptamers, considering the rapid advancements in this area, and discussed their applications in biological and chemical detection. Finally, we delved into the current challenges and future directions in the development of aptamer and aptamer-based LFS. Although this review was not thoroughly, it would serve as a valuable reference for understanding the research progress of aptamer-based LFS and aid in the development of new types of aptasensors.

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Animal diseases often have significant consequences due to the unclear and time-consuming diagnosis process. Furthermore, the emergence of new viral infections and drug-resistant pathogens has further complicated the diagnosis and treatment of viral diseases. Aptamers, which are obtained through systematic evolution of ligands by exponential enrichment (SELEX) technology, provide a promising solution as they enable specific identification and binding to targets, facilitating pathogen detection and the development of novel therapeutics. This review presented an overview of aptasensors for animal virus detection, discussed the antiviral activity and mechanisms of aptamers, and highlighted advancements in aptamer-based antiviral research following the COVID-19 pandemic. Additionally, the challenges and prospects of aptamer-based virus diagnosis and treatment research were explored. Although this review was not exhaustive, it offered valuable insights into the progress of aptamer-based antiviral drug research, target mechanisms, as well as the development of novel antiviral drugs and biosensors.

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ObjectiveTo investigate the role and mechanism of podoplanin （PDPN） in hepatic stellate cell （HSC） activation and liver fibrosis. MethodsLiver biopsy samples were collected from 75 patients with chronic hepatitis B who attended Department of Infectious Diseases， Putuo Hospital Affiliated to Shanghai University of Traditional Chinese Medicine， for the first time from September 2019 to June 2022， and RT-PCR and immunohistochemistry were used to measure the expression of PDPN in liver tissue of patients in different stages of liver fibrosis. A total of 12 male C57/BL6 mice were randomly divided into control group and model group. The mice in the model group were given intraperitoneal injection of 10% CCl4， and those in the control group were injected with an equal volume of olive oil， for 6 weeks. HE staining and Sirius Red staining were used to observe liver histopathological changes； primary mouse liver cells were separated to measure the mRNA expression of PDPN in various types of cells； primary mouse HSCs were treated with PDPN protein， followed by treatment with the NF-‍κB inhibitor BAY11-708， to measure the expression of inflammatory factors in HSCs induced by PDPN. The independent-samples t test was used for comparison of normally distributed continuous data between two groups； a one-way analysis of variance was used for comparison between multiple groups， and the least significant difference t-test was used for further comparison between two groups. The Spearman correlation analysis was used to investigate data correlation. ResultsAs for the liver biopsy samples， there was a relatively low mRNA expression level of PDPN in normal liver， and there was a significant increase in the mRNA expression level of PDPN in liver tissue of stage S3 or S4 fibrosis （all P<0.001）. Immunohistochemical staining showed that PDPN was mainly expressed in the fibrous septum and the hepatic sinusoid， and the PDPN-positive area in S4 liver tissue was significantly higher than that in S0 liver tissue （t=8.892， P=0.001）. In normal mice， PDPN was mainly expressed in the hepatic sinusoid， and there was a significant increase in the expression of PDPN in CCl4 model mice （t=0.95， P<0.001）， mainly in the fibrous septum. RT-PCR showed a significant increase in the mRNA expression of PDPN in the CCl4 model mice （t=11.25， P=0.002）. Compared with hepatocytes， HSCs， Kupffer cells， and bile duct endothelial cells， hepatic sinusoidal endothelial cells showed a significantly high expression level of PDPN （F=20.56， P<0.001）. Compared with the control group， the primary mouse HSCs treated by PDPN protein for 15 minutes showed significant increases in the mRNA expression levels of the inflammation-related factors TNFα， CCL3， CXCL1， and CXCR1 （all P<0.05）， and there were significant reductions in the levels of these indicators after treatment with BAY11-7082 （all P<0.05）. ConclusionThere is an increase in the expression of PDPN mainly in hepatic sinusoidal endothelial cells during liver fibrosis， and PDPN regulates HSC activation and promotes the progression of liver fibrosis via the NF-κB signaling pathway.

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ObjectiveTo investigate the mechanism of action of Xiayuxue decoction in inhibiting nonalcoholic fatty liver disease （NAFLD） induced by high-fat diet in mice by regulating nucleotide binding oligomerization domain like receptor containing pyrin domain protein 6 （NLRP6）. MethodsA total of 15 male C57BL/6 mice were randomly divided into low-fat diet （LFD） group， high-fat diet （HFD） group， and Xiayuxue decoction-HFD group （XYXD group）， with 5 mice in each group. Liver function parameters （alanine aminotransferase ［ALT］ and aspartate aminotransferase ［AST］） and blood lipid metabolic indicators （triglycerides ［TG］ and total cholesterol ［TC］） were measured； HE staining and oil red O staining were performed for liver tissue to observe histomorpholoty and lipid droplet deposition； quantitative real-time PCR was used to measure the expression levels of inflammatory factors （tumor necrosis factor-α ［TNF-α］， interleukin-1β ［IL-1β］， interleukin-18 ［IL-18］， and NLRP6） in liver tissue； Western blot was used to measure the protein expression levels of NLRP6， nuclear factor-kappa B （NF-κB）， and NF-κB p65； immunohistochemistry was used to measure the expression of NLRP6 and CD68. Mouse Raw264.7 cells were treated with palmitic acid （PA）， lipopolysaccharide， and serum containing Xiayuxue decoction to observe inflammation. A one-way analysis of variance was used for comparison of continuous data between multiple groups， and the least significant difference t-test was used for further comparison between two groups. ResultsCompared with the LFD group， the HFD group had significant increases in the serum levels of ALT， AST， TC， and TG （all P<0.05）. Liver histopathological examination showed that the HFD group had marked hepatic steatosis and a signficant increase in NAS score （P<0.05）， and quantitative real-time PCR showed significant increases in the inflammatory factors such as IL1β and IL-18 and a significant reduction in the expression of NLRP6 （all P<0.05）. Immunohistochemistry showed that the expression of NLRP6 showed a similar trend as that of the macrophage marker CD68. Western blot showed that after the downregulation of NLRP6 expression， there was a significant increase in phosphorylated NF-κB p65 （P<0.05）. Compared with the HFD group， Xiayuxue decoction effectively improved liver inflammation， upregulated the expression of NLRP6， and downregulated phosphorylated NF-κB p65 in HFD mice （all P<0.05）. After Raw264.7 cells were treated with PA， NLRP6 was downregulated to promote the progression of inflammation （P<0.05）， and treatment with Xiayuxue decoction could upregulate NLRP6 and inhibit inflammation NF-κB （P<0.05）. ConclusionXiayuxue decoction can effectively improve hepatic steatosis and liver inflammation in a mouse model of NAFLD， possibly by regulating NLRP6/NF-κB to alleviate macrophage activation.

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BACKGROUND: Atherosclerotic renal artery stenosis (ARAS) is a common disease in the elderly population. OBJECTIVE: The aim was to develop a contrast-enhanced ultrasound (CEUS)-based model for predicting post-angioplasty improvement in hypertension in patients with severe ARAS. METHODS: Thirty-five patients with severe ARAS (⩾ 70%) were included in this study, and 42 renal arteries received percutaneous transluminal renal arterial stenting. An optimal integral formula was developed from pre-interventional color-coded duplex sonography (CCDS) and CEUS parameters using least absolute shrinkage and selection operator (LASSO) regression and receiver operating characteristic (ROC) curve analysis. A model for predicting short-term hypertension improvement was established using the integral formula and clinical risk factors. Bootstrapping was used for internal validation. RESULTS: Two integral formulas, LASSO.CCDS and LASSO.CEUS, were established. ROC curves of the two integral formulas showed that LASSO.CEUS was the better formula for predicting hypertension improvement (AUC 0.816, specificity 78.6%). Univariate and multivariate regression analyses showed that duration of hypertension (OR 0.841, P= 0.027), diabetes (OR = 0.019, P= 0.010), and LASSO.CEUS (OR 7.641, P= 0.052) were predictors of short-term hypertension improvement after interventional therapy. Using LASSO.CEUS combined with clinical risk factors, the following prediction model was established: logit (short-term improvement in hypertension) = 1.879-0.173 × hypertension duration - 3.961 × diabetes + 2.034 × LASSO.CEUS (AUC 0.939). CONCLUSIONS: The model established using CEUS parameters and clinical risk factors could predict hypertension improvement after interventional therapy, but further research and verification are needed.

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Contamination in food and the environment with fluoroquinolones (FQs) has become a serious threat to the global ecological balance and public health safety. Ofloxacin (OFL) is one of the most widely utilized sterilization agents in FQs. In the process of monitoring OFL, broad-spectrum monoclonal antibodies (mAb) cannot meet the demand for monospecific detection. Here, a computational chemistry-assisted hapten screening strategy was proposed in this study. Differences in the properties of antigenic epitopes were precisely extracted through a comprehensive comparative study of 16 common FQs molecules and a monospecific and ultrasensitive mAb-3B4 for OFL was successfully prepared. The screened fleroxacin (FLE) hapten was applied in a heterologous competition strategy resulting in a 20-fold improvement in the half inhibitory concentration (IC50) of mAb-3B4 to 0.0375 µg L-1 and cross-reacted only with marbofloxacin (MAR) in regulated FQs. In addition, a single-chain variable fragment (scFv) for OFL was constructed for the first time with an IC50 of 0.378 µg L-1. Molecular recognition mechanism studies validated the reliability of this strategy and revealed the key amino acid sites responsible for OFL specificity and sensitivity. Finally, ic-ELISA and GICA were established for OFL in real samples. This work provides new ideas for the preparation of monospecific mAb and improves the monitoring system of FQs.

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There is an urgent need to develop an economical and convenient method for the ultrasensitive detection of patulin (PAT), a mycotoxin that can potentially harm human health when it is found in fruits and their derivatives. In this study, we have developed a novel fluorescent aptasensor that utilizes nitrogen-doped carbon dots (N-CDs) as the fluorescent donor and hexagonal ß-Co(OH)2 nanoplates as the fluorescent acceptor. N-CDs were synthesized through the hydrothermal method, resulting in spherical particles with a diameter of 7.6 nm. These nanoparticles exhibited excellent water solubility and displayed a vibrant blue emission at 448 nm when excited at 360 nm. Cobalt hydroxide nanoplates with a beta crystal structure [ß-Co(OH)2] were synthesized using a simple co-precipitation method, exhibiting hexagonal plate-like shapes with uniform lateral sizes of 4-5 µm. The fluorescence of N-CDs can be efficiently quenched by hexagonal ß-Co(OH)2 nanoplates through Förster resonance energy transfer mechanism. The maximum quenching-recovery capability can be achieved when the concentrations of N-CDs-Apt and ß-Co(OH)2 nanoplates are 150 nmol/L and 100 µg/mL, respectively. The pH of the TE buffer should be 8.0, and the incubation time should be 10 min at 25 °C. The developed fluorescent aptasensor displayed an excellent selectivity for PAT determination with a detection limit of 0.57 pg/mL in the linear range of 1.25 pg/mL-100 ng/mL. The rapid PAT determination in fruit juice samples was realized with good recoveries (96.9-105.8%). The developed fluorescent aptasensor based on the interaction between N-CDs and hexagonal ß-Co(OH)2 nanoplates can be a promising method for the rapid and ultrasensitive detection of PAT in agricultural products.

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BACKGROUND: Sleep problems and cognitive changes are typical in pregnant women with depressive symptoms. However, the relationship between sleep quality and executive dysfunction remains unclear. This study aims to explore the differences in sleep quality and cognitive inhibition between pregnant women with and without depressive symptoms in the third trimester of pregnancy and investigate the correlations between sleep quality, cognitive inhibition and depressive symptoms. METHODS: In the third trimester, 169 women without depressive symptoms and 88 women with depressive symptoms participated in the study. Edinburgh Postpartum Depression Questionnaire (EPDS) was used to assess depressive symptoms, and Pittsburgh Standard Sleep Quality Index Questionnaire (PSQI) was used to investigate sleep quality. The color-word Stroop task is used to evaluate cognitive inhibition. RESULTS: Compared with women without depressive symptoms, pregnant women with depressive symptoms showed worse sleep quality and Stroop task performances (response speed and accuracy). In addition, the speed of cognitive inhibition plays a mediating role in the relationship between sleep quality and prenatal depressive symptoms. CONCLUSION: This research emphasizes the importance of sleep quality screening and cognitive training for depression during pregnancy and childbirth in ensuring women's mental health during pregnancy and childbirth.

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The monitoring of sulfadiazine (SDZ) is of great significance for food safety, environmental protection, and human health. In this study, a fluorescent aptasensor based on MnO2 and FAM-labeled SDZ aptamer (FAM-SDZ30-1) was developed for the sensitive and selective detection of SDZ in food and environmental samples. MnO2 nanosheets adsorbed rapidly to the aptamer through its electrostatic interaction with the base, providing the basis for an ultrasensitive SDZ detection. Molecular dynamics was used to explain the combination of SMZ1S and SMZ. This fluorescent aptasensor exhibited high sensitivity and selectivity with a limit of detection of 3.25 ng/mL and a linear range of 5-40 ng/mL. The recoveries ranged from 87.19% to 109.26% and the coefficients of variation ranged from 3.13% to 13.14%. In addition, the results of the aptasensor showed an excellent correlation with high-performance liquid chromatography (HPLC). Therefore, this aptasensor based on MnO2 is a potentially useful methodology for highly sensitive and selective detection of SDZ in foods and environments.

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The study investigates a bimetallic organic framework (Zn/Eu-MOF) based fluorescent probe for visual detection of ofloxacin (OFL) in pork, beef and fish. The developed sensing probe recognizes OFL through internal filtration and cation-π interaction between OFL and Zn/Eu-MOF, resulting in a distinct color change from orange-red to light green. The content of OFL can be determined through RGB analysis by a mobile-phone. The developed sensing probe offers several advantages such as broad linear range (0.1 âˆ¼ 80 µM), rapid response time (30 s), low detection line (0.44 µM). The effectiveness of the sensing probe can last for five rounds with good recovery. Moreover, the application of the sensing probe on pork, beef and fish samples are reliable, with recoveries ranging from 93.4 to 112.1%, and the relative standard deviations (RSD) within 1.17% to 2.06%. These results suggest that the developed sensing probe could have significant potential for practical on-site test in food.

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Pymetrozine is a neonicotinoid insecticide with high efficacy against aphids and planthoppers, and has been used worldwide. To monitor its residue in food, a highly specific and sensitive monoclonal antibody (McAb) was prepared, and an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed to detect pymetrozine, with a 50% inhibition value (IC50) of 7.70 µg/L. The McAb showed little affinity for acetamiprid, hexazinone, metamitron, nitenpyram, metribuzin, and imidacloprid. The limits of detection (LOD) calculated from the analysis of broccoli, cabbage, wheat, maize, rice, chicken, fish, and crayfish samples were from 1.56 to 2.72 µg/kg and the average recoveries were from 81.25 to 103.19%. icELISA was confirmed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). These results demonstrated that the optimised icELISA is a convenient and effective analytical tool for monitoring pymetrozine residues in food.

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Nitrofurazone (NFZ) is an antibiotic banned in many countries, as its residue seriously harms the human body. Herein, anti-NFZ aptamers were selected and identified based on the magnetic bead SELEX technique using a ssDNA library with a full length of 90 nucleotides (nt). Five full sequence candidate aptamers (NFZ8, NFZ24, NFZ28, NFZ34, and NFZ70) were obtained by secondary structure analysis. We optimized the entire sequence to obtain a truncated aptamer, a 16 nt sequence (NFZ8-1:5'-GTTCTATTGAAAAAAC-3') that showed the highest affinity for NFZ (Kd = 76.11 nM). The binding site of NFZ and aptamer NFZ8-1 was found to be "GAA" by molecular docking. In addition, utilizing the most special truncated aptamer NFZ8-1 as the identification probe, a graphene oxide fluorescent aptasensor is an innovative for the detection of NFZ residue that showed a wide linear reach from 1.25 to 160 ng/mL and a low limit of detection of 1.13 ng/mL. In the actual water environment sample detection, the recovery rate ranged from 95.21 to 113.66%, and the coefficient of variation ranged from 3.53 to 11.24%. These results demonstrate that the NFZ-truncated aptamer applied to the aptasensor provides a novel methodology for recognizing NFZ residues.

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The widespread of patulin (PAT) and its potential hazards to human health call for alternative rapid assays to monitor it in food and the environment. Herein, we prepared chromium hydroxide [Cr(OH)3] nanoparticles via a one-pot chemical precipitation strategy and used them to fabricate a turn-on fluorescent aptasensor employing a morphological effect for sensitive PAT detection. Three Cr(OH)3 nanoparticle structures were synthesized by changing the solvent, and their structures and physicochemical properties were investigated. Then, we evaluated the effects of morphological structures on the fluorescence quenching-recovery capability of Cr(OH)3 nanoparticles before and after incubation with PAT. We found that the Cr(OH)3-3 nanoparticles efficiently absorbed the fluorescence dye 6-carboxyfluorescein labeled aptamer (FAM-Apt) and quenched the fluorophore through photoinduced electron transfer. Under optimal experimental conditions, the turn-on fluorescent aptasensor for PAT determination displayed two linear ranges (0.01-10 ng/mL and 1-200 ng/mL) with a low detection limit of 7.3 pg/mL. Moreover, the proposed aptasensor had no cross-reactivity with interferents that usually coexist with PAT and can be used to detect PAT in apple juices accurately. The results of the as-fabricated method were not significantly different from the high-performance liquid chromatography. Hence, we demonstrated that different Cr(OH)3 nanoparticles can be prepared by changing reaction conditions, and provided a novel strategy to improve the detection performance of fluorescent aptasensor by changing the morphological structure and crystalline properties of nano-quenchers.

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Doxycycline (DOX) and its metabolite residues in food and the environment pose a serious threat to human health and the ecological environment. In this work, a novel method, termed competitive fluoroimmunoassays (cFIA), based on monoclonal antibody (mAb) bio-conjugated CdSe/ZnS core-shell quantum dots (QDs), was developed for sensitive and rapid bioanalyses of DOX in natural water and commercial meats. After the optimization of the experimental conditions, 1 µg mL-1 of coating antigen and 0.5 µg mL-1 of QD-labeled mAb were used for the establishment of the cFIA. With this assay, the 50% inhibition concentration was found to be 0.35 ng mL-1 of DOX in phosphate-buffered saline samples, and the limit of detection was 0.039 ng mL-1 with minor cross-reactivity to other tetracycline members. The recoveries from natural water and commercial meats spiked with DOX concentrations of 10-600 ng mL-1 were 81.3-109.8%, and standard deviation were all below 12%. Levels measured with the QD-cFIA for thirty authentic samples were confirmed by high-performance liquid chromatography with good correlations. These results indicate that QD-cFIA is sultable for the rapid and quantitative detection of DOX residue in environmental and food samples.

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In this study, we developed a fluorescent aptasensor based on Fe3O4/Au/g-C3N4 and a FAM-labeled aptamer (FAM-SMZ1S) against sulfamethazine (SMZ) for the specific and sensitive detection of SMZ in food matrix. The FAM-SMZ1S was adsorbed by the Fe3O4/Au/g-C3N4 via π-π stacking and electrostatic adsorption, serving as a basis for the ultrasensitive detection of SMZ. Molecular dynamics was used to explain the reasons why SMZ1S and SMZ were combined. This aptasensor presented sensitive recognition performance, with a limit of detection of 0.16 ng/mL and a linear range of 1-100 ng/mL. The recovery rate ranged from 91.6% to 106.8%, and the coefficient of variation (CV) ranged from 2.8% to 13.4%. In addition, we tested the aptasensor for the monitoring of SMZ in various matrix samples, and the results were well-correlated (R2 ≥ 0.9153) with those obtained for HPLC detection. According to these results, the aptasensor was sensitive and accurate, representing a potentially useful tool for the detection of SMZ in food matrix.

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