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Metal-organic frameworks (MOFs) are a large class of crystalline porous materials that composed of organic ligands and metal ions, of which zeolitic imidazolate frameworks (ZIFs) are a broad classification. The most well-known ZIF-like material is ZIF-8 crystals, which have been the subject of extensive research for decades. ZIF-8 crystals have been synthesized under various conditions for application in the fields of sensing, drug delivery, and catalysis. This paper provides a brief introduction to the preparation methods, formation processes, and formation mechanisms of ZIF-8 crystals in different media, and then explains the effects of different precursor conditions (type of Zn2+, ratio of raw materials, and type of solvent) on ZIF-8 crystals in terms of formation mechanisms. Subsequently, current reports on the application of ZIF-8-based chemiresistive gas sensors, electrochemical, fluorescent and colorimetric sensors are also summarized. Hopefully, ZIF-8 crystals with good catalytic properties will be obtained based on rational design for promoting the application in different fields of the sensors. [ABSTRACT FROM AUTHOR]

AbstractImmunoassay based on the antibodies specific for targets has advantages of high sensitivity, simplicity and low cost, therefore it has received more attention in recent years, especially for the rapid detection of small molecule chemicals present in foods, diagnostics and environments. However, limited by low molecular weight and only one antigenic determinant existed, immunoassays for these small molecule chemicals, namely hapten substances, were commonly performed in a competitive immunoassay format, whose sensitivities were obviously lower than the sandwich enzyme-linked immunosorbent assay generally adaptable for the protein targets. In order to break through the bottleneck of detection format, researchers have designed and established several novel noncompetitive immunoassays for the haptens in the past few years. In this review, we focused on the four representative types of noncompetitive immunoassay formats and described their characteristics and applications in rapid detection of small molecules. Meanwhile, a systematic discussion on the current technologies challenges and the possible solutions were also summarized. This review aims to provide an updated overview of the current state-of-the-art in noncompetitive immunoassay for small molecules, and inspire the development of novel designs for small molecule detection. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the differences, including organic acid, free amino acid, and volatile compound contents, in soy sauces obtained at different fermentation stages (stage A, Touyou ; stage B, Eryou ; stage C, Sanyou). The result showed that the content of total organic acids in Eryou (400.41 mg/kg) and Sanyou (393.95 mg/kg) was significantly higher than that in Touyou (376.52 mk/kg), even though lactic acid content showed no significant differences, which was the dominant organic acid among the three soy sauces. However, the total free amino acid content of Touyou (7.73 g/kg) was significantly higher than that of Eryou (5.82 g/kg) and Sanyou (6.44 g/kg). Moreover, the umami and bitter free amino acid contents in Touyou were significantly higher than those in Eryou (p < 0.50). Besides, Touyou and Sanyou showed the highest peak intensities of alcohols (130157.08) and acids (77943.05), respectively. PLS-DA showed that the soy sauces from different fermentation stages were well separated from each other based on the volatile compounds, and 19 volatile components were selected characteristic volatile compounds with VIP > 1. Thus, these differences in organic acid, free amino acid and volatile compound contents resulted in the variability in flavor and quality of Cantonese soy sauces at different fermentation stages. [Display omitted] • Eryou and Sanyou exhibit similar color, and pH. • The content of organic acids in Eryou and Sanyou was higher than that in Touyou. • The content of total free amino acid in Touyou was higher than that in Eryou and Sanyou. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PSTs) are biotoxins derived from harmful algal blooms and cause paralytic shellfish poisoning (PSP). PSTs are widely found in natural waters, indicating that they can cause human death through food chain and economic losses of aquatic species worldwide. Therefore, accurate, sensitive, and efficient methods are needed for the detection of PSTs in the environment and food. Biosensor is one of the fastest-growing detection methods since they are simple, sensitive, portable, and efficient for real-time or near real-time analyses. This article provides a comprehensive review of PSTs biosensors by highlighting different signaling mechanisms (electrochemical, optical, etc.). Typically, the effects of the generation of bio-recognition elements on PSTs sensing performance to expand new biosensors applications which were highlighted. Although mouse bioassay and HPLC are the current methods used for PSTs detection, biosensor could become an alternative method for PSTs detection in the future. Although antibodies are the most popular affinity-based recognition elements, aptamers have been rapidly developed in recent years to mimic antibodies. As a result, biosensor detection of PSTs mainly focuses on electrochemical and optical signal transduction. Nonetheless, robust, accurate, and portable biosensors are needed for real application and commercialization. [Display omitted] • MerIts and demerits of bio-recognition elements for detceting PSTs were summarized. • Recent advanced biosensors methods for paralytic shellfish toxins was reviewed. • Electrochemical and optical signal transduction based biosensors had been strengthen. • AntiBodies and adaptors showed potential for development of practical biosensors. [ABSTRACT FROM AUTHOR]

Rising living standards have heightened the demand for fresh, safe, and nutritious food, necessitating advanced food quality and safety monitoring technologies. Electrospun nanofibers (ENFs) are gaining increasing attention as key materials in the development of high-performance sensing platforms for food safety and quality monitoring owing to their high surface area, porosity, and customizable structures. This review provides a comprehensive overview of recent advances in the application of ENFs for food analysis. It highlights their roles and mechanisms in detecting environmental toxins, identifying foodborne pathogens, analyzing food components, and monitoring freshness. Furthermore, the benefits, limitations, and future development directions of ENFs in food analysis are discussed. ENFs can serve as effective materials for sample pretreatment, enhancing detection sensitivity, streamlining procedures, and reducing detection times through target analyte adsorption and enrichment. They also hold considerable potential as scaffolds for sensors that enable rapid and accurate detection of various food analytes. However, challenges related to standardization and environmental impact must be addressed to transition ENFs from laboratory research to practical applications. [Display omitted] • Applications of ENFs in food analysis are comprehensively reviewed. • Roles and merits of ENFs in food analysis are summarized. • The latest developments in detecting toxins, pathogens, and food freshness using ENFs are reviewed. • Remaining limitations and potential of ENFs for food analysis are discussed. [ABSTRACT FROM AUTHOR]

The absence of high-affinity antibodies has hindered the development of satisfactory immunoassays for dichlorvos (DDVP) and trichlorfon (TCP), two highly toxic organophosphorus pesticides. Herein, the de novo synthesis of a novel anti-DDVP hapten was introduced. Subsequently, a specific anti-DDVP monoclonal antibody (Mab) was produced with satisfying affinity to DDVP (IC 50 : 12.4 ng mL−1). This Mab was highly specific to DDVP, and TCP could readily convert into DDVP under mild alkaline conditions. Leveraging this insight, an indirect competitive ELISA was successfully developed for simultaneous detection of DDVP and TCP. The limit of detection in rice, cabbage and apple for DDVP /TCP was found to be 12.1/14.6 μg kg−1, 7.3/8.8 μg kg−1 and 6.9/8.3 μg kg−1, respectively. This study not only provides an effective strategy for producing a high-quality anti-DDVP Mab but also affords a reliable and cost-effective tool suitable for high-throughput detection of DDVP and TCP in food samples. [Display omitted] • The de novo synthesis of a novel anti-DDVP hapten was introduced. • A specific anti-DDVP monoclonal antibody with a satisfying affinity was produced. • TCP was found readily convert into DDVP in a borate buffer at pH 8.0. • An ic-ELISA for the detection of DDVP and TCP was firstly developed. [ABSTRACT FROM AUTHOR]

Nitrite is a well-known food additive and water pollutant that has garnered extensive attention due to both of its adverse and beneficial effects on human health, calling for rapid and reliable analytical methods. However, the simple and diminutive structure of nitrite has impeded the development of screening immunoassay for this substance. In this work, based on the rapid and selective derivatization of nitrite into benzotriazole (BTA) by o-phenylenediamine, two haptens targeting the structure of BTA were designed and synthesized, and a specific monoclonal antibody against BTA was generated. Using this antibody, an indirect competitive enzyme-linked immunosorbent assay (ELISA), involving a rapid pre-analysis derivatization, was developed for the detection of nitrite in foods. The limits of detection in drinking water, pickle, and ham sausage were 2.0 μg/L, 0.05 mg/kg, and 0.05 mg/kg, respectively. The recoveries ranged from 82.7% to 114.6%, and the results of this ELISA correlated well with those from the standard spectrophotometry method. This pioneering immunoassay for nitrite holds great promise for routine monitoring, ensuring food safety and consumer health. • Haptens against benzotriazole (BTA) was firstly synthesized. • A highly specific anti-BTA monoclonal antibody was generated. • A rapid nitrite derivatization strategy suitable for ELISA was designed. • An ic-ELISA for high-throughput detection of nitrite was firstly developed. [ABSTRACT FROM AUTHOR]

Thua-Nao , a traditional fermented soybean product in Thailand, is susceptible to contamination with biogenic amines (BAs), thus increasing the risk to human health. The present study evaluated the contamination, formation, and risk assessments of BAs in two types of Thua-Nao. The elution conditions were optimized and used to analyze thua nao BAs with good correlation coefficients and high recovery. The average total BA content in dried Thua-Nao (D-TN; 342 mg/kg) was greater than that in fresh Thua-Nao (F-TN; 239 mg/kg), but the difference was not significant. Tyramine (TYM) was the dominant BA in thua nao , accounting for more than half of the total BAs in the majority of the samples, and it also exhibited a significant positive correlation with soluble protein and total BAs. The calculated highest estimated daily intake (EDI) and index of food safety (IFS) of TYM were 1.51 μg/kg/day and 0.008, respectively, among the age groups who consumed thua nao , indicating a low risk to human health. However, the acute risk index of TYM in F-TN and D-TN among patients taking monoamine oxidase inhibitors (MAOIs) was greater than 80 %. Thus, these results suggested that an adverse health effect is unlikely for the general population after excessive consumption of TYM-contaminated Thua-Nao , but it may have serious health implications for patients taking MAOIs. • The contamination of biogenic amines in thua nao were analyzed through the optimized HPLC. • Tyramine was the dominant BAs in thua nao correlating with soluble protein and total BAs. • BAs wouldn't formed during thua nao drying and storage period. • BAs exposure from thua nao would be of low potential health concern for the health population. • A relatively high health risk of TYM dietary was observed in MAOI patients. [ABSTRACT FROM AUTHOR]

Gizzerosine is a biogenic amine produced in fish meal drying process and posted higher mortality due to gizzard erosion in poultry than histamine. However, it is difficult to obtain gizzerosine and achieve sensitive practical detection due to its simple structure. Herein, a monoclonal antibody (mAb) specific to gizzerosine was generated based on the new structural design and a fluorescence immunosensor for sensitive and on-site detection of gizzerosine in feed was first established. Molecular modeling of the three-dimensional (3D) structure and surface electrostatic potential of gizzerosine indicated that the carbonyl group of gizzerosine hapten might affect the important sites of antigen-antibody interactions. The proposed structure was used to obtain the sensitive and specific mAb with IC 50 of 3.88 ng/mL in indirect competitive ELISA which was approximately 100-fold lower than that of direct competitive ELISA. Considering the practical application scenarios, a fluorescence immunosensor based on microporous dry method integrated with independent quality control line was established to improve detection stability. Under the optimum conditions, the proposed immunosensor showed a good linear relationship from 1.10 to 19.78 ng/mL and provided a low detection limit of 50 ng/g which was approximately 80-fold lower than the maximum recommended amount (0.4 mg/kg) of gizzerosine in feed. The recoveries of 6 kinds of feed ranged from 83.1 % to 114.3 %, which was in good consistence with that of UHPLC–MS/MS. Overall, this work provides a fast, cost-effective and reliable on-site tool for rapid screening of gizzerosine residues in feed samples. [Display omitted] • A novel hapten different from the original gizzerosine was designed for the first time. • A highly sensitive and specific anti-gizzerosine monoclonal antibody based on the novel hapten was prepared. • Relationship between antibody and hapten was studied by molecular modeling. • A fluorescence immunosensor was firstly developed for the on-site detection of gizzerosine. • The microporous dry method integrated with independent quality control line can be used for on-site detection. [ABSTRACT FROM AUTHOR]

The accumulation of quinalphos pesticide in agricultural products have detrimental effects to human body and environment, hence, an efficient and sensitive detection approach is desirable. In this study, a label-free electrochemical immunosensor based on the directly immobilizing nanobody onto functionalized polyvinyl alcohol/gelatin-gold nanoparticles nanofiber membrane (PVA/G-AuNPs NFM) was fabricated. First, a homogeneous PVA/G-AuNPs NFM with multiple-porosity structure and appropriate hydrophilicity was prepared. Then, the electrochemical immunosensor was assembled and under the optimized conditions, the prepared biosensor exhibited good detection performance towards quinalphos with the linear range and limit of detection being 0.06–1000 ng/mL and 50.74 pg/mL (S/N = 3), respectively. Moreover, the sensor presented good specificity, regenerability and stability, maintaining more than 90% activity after 5 times of regeneration and about 90% activity after 6 weeks of storage. Finally, the average recoveries of quinalphos from food samples were 89.68%–110.88% with the coefficient of variation being 1.65%–7.81%, showing good correlation with UPLC-MS/MS (R2 = 0.9859), indicating the accuracy of the proposed electrochemical immunosensor assay. Overall, the label-free electrochemical immunosensor presents a novel approach for the rapid and sensitive detection of quinalphos and other pesticide residues. • A label-free biosensor platform based on nanofiber-coupled nanobody was developed. • Nanobody was immobilized onto the nanofiber's surface based on the Schiff reaction. • Nanofiber's microstructure and functionalization facilitated detection sensitivity. • The biosensor exhibited good specificity, reproducibility and long-term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A UHPLC–MS/MS method for simultaneous sensitive detection of gizzerosine and histamine in feeds and raw materials was established first. • The matrix effects were reduced by MCX-SPE. • A short time normal temperature hydrolysis pretreatment method was developed to facilitate real-time monitoring. Gizzerosine is a biogenic amine in feeds with a physiological toxicity 1,000 times that of its precursor, histamine, causing high mortality in poultry. Because feeds containing gizzerosine usually contain high concentrations of histamine, it is of great significance to establish a method for the simultaneous detection of gizzerosine and histamine for feed safety. Herein, we first developed a detection method using 50 % (v/v) acetonitrile(ACN) containing 1 % (v/v) ammonium hydroxide (AH) extraction to synchronously monitor gizzerosine and histamine in feeds and raw materials via UHPLC–MS/MS. Due to the serious positive matrix effect (ME) in existing LC–MS/MS, this study reduced the ME of samples by purifying the extract solution using a mixed-mode cation exchange based solid phase extraction column (MCX-SPE), and simultaneously obtained accurate quantities of 5–500 ng mL−1 gizzerosine and 25–2,500 ng mL−1 histamine. The limit of detection (LOD) values for gizzerosine and histamine were 1.02 ng mL−1 and 3.00 ng mL−1, respectively, which were approximately 390 and 8,000 times more sensitive than the maximum recommended dosage of gizzerosine (0.4 mg kg−1) and limitation standards of histamine (25 mg kg−1) in fish meal, respectively. The samples could only be evaluated in 2 h. The average recoveries of the 6 types of feeds and raw materials ranged from 79.73 % to 110.31 % with a relative standard deviation (RSD) ranging from 1.29 % to 13.35 %. The average recoveries of feeds were generally lower than those of raw materials. Our method was efficient, simple, rapid, accurate, sensitive, and suitable for the simultaneous quantitative analysis of gizzerosine and histamine contents in various feeds, which provided technical support for the quality evaluation of feeds. [ABSTRACT FROM AUTHOR]

Eugenol compounds (EUGs), which share chemical similarities with eugenol, belong to a group of phenolic compounds primarily found in clove oil. They are highly valued by fish dealers due to their exceptional anesthetic properties, playing a crucial role in reducing disease incidence and mortality during the transportation of live fish. Despite their widespread use, the safety of EUGs remains a contentious topic, raising concerns about the safety of aquatic products. This underscores the need for efficient and sensitive analytical methods for detecting EUGs. Nanomaterial-based ratiometric fluorescence immunoassay has gained increasing attention due to its integration of the immunoassay's excellent specificity and compatibility for high-throughput analysis, coupled with the exceptional sensitivity and anti-interference capabilities of ratiometric fluorescence assays. In this study, we developed a sensitive ratiometric fluorescence immunoassay for screening five EUGs. This method employs a broad-specificity monoclonal antibody (mAb) as a recognition reagent, selective for five EUGs. It leverages the horseradish peroxidase (HRP)-triggered formation of fluorescent 2,3-diaminophenazine (DAP) and the quenching of fluorescent gold clusters (Au NCs) for detection. The assay's detection limits for eugenol, isoeugenol, eugenol methyl eugenol, methyl isoeugenol, and acetyl isoeugenol in tilapia fish and shrimp were found to be 9.8/19.5 μg/kg, 0.11/0.22 μg/kg, 19/36 Tilapia ng/kg, 8/16 ng/kg, and 3.0/6.1 μg/kg, respectively. Furthermore, when testing spiked Tilapia fish and shrimp samples, recoveries ranging from 84.1 to 111.9 %, with the coefficients of variation staying below 7.1 % was achieved. This work introduces an easy-to-use, broad-specificity, and highly sensitive method for the screening of five EUGs at a pg/mL level, which not only provides a high-throughput strategy for screening eugenol-type fish anesthetics in aquatic products, but also can serve as a benchmark for developing immunoassays for other small molecular pollutants, rendering potent technological support for guarding food safety and human health. [Display omitted] • BSA-Au NCs was introduced into the substrate system for ratiometric fluorescence immunoassay. • High-throughput screening five EUGs residue was attained. • Ultrasensitive detection of EUGs at pg/mL level was achieved. [ABSTRACT FROM AUTHOR]

Multicolor-based visual immunosensor is a promising tool for rapid analysis without the use of bulky instruments. Herein, an anti-fenitrothion nanobody-alkaline phosphatase fusion protein (VHHjd8-ALP) was employed to develop a multicolor visual immunosensor (MVIS) and a ratiometric fluorescence MVIS (RFMVIS, respectively). After one-step competitive immunoassay, the VHHjd8-ALP bound to microplate catalyzed phenyl phosphate disodium salt (ArP) into phenol. Under high alkaline condition (pH 12), the phenol reduced KMnO 4 to intermediate (K 2 MnO 4) and further to MnO 2 in alkaline condition (pH 12), accompanied by a visible color transition of purple-green-yellow, which can be used for semiquantitative visual analysis or qualitative detection by measuring RGB value. RFMVIS was proposed on the basis of MVIS to further improve sensitivity. The CdTe quantum dot and fluorescein were used as signal probes to develop the fluorescent immunosensor. The CdTe dots with red emission (644 nm) was quenched by oxidation of KMnO 4 , whereas the fluorescein with green emission (520 nm) remained constant, accompanied by a fluorescent color transition of green-yellow-red. By measuring the ratio of the fluorescence intensity (I 644 /I 520), the ratiometric fluorescence immunosensor was developed for qualitative analysis. The two visual immunosensors were sensitive and simple, and they showed good accuracy and practicability in the recovery test, thus are ideal tools for rapid screening. [ABSTRACT FROM AUTHOR]

Immunochromatographic assay (ICA) has been used widely for the onsite monitoring of illegal additives due to its simplicity, speed, and low cost. However, a scanner is commonly required for ICA to achieve quantitative results. In this work, we developed a visual semi-quantitative ICA for sibutramine, a banned additive in diet foods, without the need for a scanner for measurement. Monoclonal antibodies specific for sibutramine were raised and conjugated with upconversion nanoparticles (UCNPs) as the luminescent tracer. ICA was developed by employing multiple test lines to achieve the semi-quantitative detection of sibutramine. Based on the optimal conditions, the cutoff levels (limit of quantitation, LOQ) of T1 line, T2 line, T3 line, and T4 line were 0.02 μg/mL, 0.15 μg/mL, 1.0 μg/mL, and 7.5 μg/mL, respectively, in buffer system. The ICA demonstrated a LOQ at 0.2 mg/kg for sibutramine in diet food samples. The assay (including pretreatment) can be finished within 30 min without the aid of other instruments, except a laser pen. No false positive or false negative results were observed. The results indicated that the proposed method was reliable, simple, and rapid for the screening of sibutramine abuse in diet food samples. [ABSTRACT FROM AUTHOR]

• PDA's triple roles of quencher, AA recognizer, and signal reporter were harnessed. • Fluorogenic substate AAP-CDs-DA was used in ultrasensitive ratiometric ALP sensing. • An ultrasensitive RF-ELISA was developed to detect benzocaine (LOD at fg/mL level). • The RF sensing platform exhibits good universality in food safety detection. Sensing alkaline phosphatase (ALP) activity with high sensitivity and accuracy is critical for both ALP-related health and food safety supervision and the development of ALP-triggered immunoassay platforms. Herein, an ultrasensitive ratiometric fluorescence (RF) sensing system based on the controllable formation of luminescent polydopamine and efficient quenching of carbon dots was proposed for the ALP activity assay, achieving quantitative detection in the range of 0.01–100 mU/L. Furthermore, this RF sensing system was integrated with an ALP-based ELISA platform to construct an RF-ELISA for benzocaine, a potentially abused anesthetic in edible fish, and ultrasensitive assay at the level of fg/mL was realized. This ratiometric strategy-based platform effectively shields various interferences through the self-calibration effect, thus providing more accurate and reliable quantification results. This study not only offers an efficient method for ultratrace detection of ALP and benzocaine but also proposes a universal platform for ultrasensitive detection of diverse targets in food analysis by replacing the recognition unit. [ABSTRACT FROM AUTHOR]

Abstract An electrochemical immunosensor for ultrasensitive detection of acrylamide (AA) in water and food samples was developed. SnO 2 -SiC hollow sphere nanochains with high surface area and gold nanoparticles with good electroconductivity were fabricated onto the surface of a glassy carbon electrode pre-coated with chitosan. The coating antigen (AA-4-mercaptophenylacetic acid-ovalbumin conjugate, AA-4-MPA-OVA) was immobilized on the electrode. Polyclonal antibody specific for AA-4-MPA was conjugated to gold nanorod (AuNR) as primary antibody (AuNR-Ab 1). Horseradish peroxidase labelled anti-rabbit antibody produced in goat was conjugated to AuNR as secondary antibody (HRP-AuNR-Ab 2). For detection, the analyte (AA-4-MPA) in sample competed with coating antigen for binding with AuNR-Ab 1. After washing, HRP-AuNR-Ab 2 was added to capture the AuNR-Ab 1 , and the electrical signal was obtained by addition of hydroquinone and H 2 O 2. After investigation of the binding ability on nanomaterials and optimization of competitive immunoassay conditions, the proposed immunosensor exhibited a sensitive response to AA with a detection limit of 45.9 ± 2.7 ng kg−1, and working range of 187 ± 12.3 ng kg−1 to 104 ± 8.2 μg kg−1 for drinking water samples. Recoveries of AA from spiked samples were ranged from 86.0% to 115.0%. The specificity, repeatability and stability of the immunosensor were also proved to be acceptable, indicating its potential application in AA monitoring. Graphical abstract Image 1 Highlights • An electrochemical immunosensor capable of detecting acrylamide sensitively and selectively was developed. • Signal amplification strategy based on chitosan/SnO2-SiC HSNC/gold nanomaterials was used. • The immunosensor was able to detect acrylamide with a LOD of 45.9 ± 2.7 ng kg−1 for drink water samples. [ABSTRACT FROM AUTHOR]

Herein, a ratiometric fluorescence (RF) immunoassay platform coupling with enzyme-nanozyme cascade amplification strategy was fabricated for precise and ultrasensitive quantification of saxitoxin (STX). In this strategy, oxidase-like cobalt oxyhydroxide nanoflakes (CoOOH NFs) catalyzed the oxidation of non-fluorescent o-phenylenediamine (OPD) into fluorescent 2,3-diaminophenazine with the maximum emission at 568 nm. This nanozyme-triggered fluorogenic reaction was cascaded with the alkaline phosphatase (ALP)-catalyzed hydrolysis of ascorbic acid 2-phosphate into ascorbic acid (AA) through the redox reaction between AA and CoOOH NFs. During the redox reaction, CoOOH NFs were reduced into Co2+ without oxidase-like activity, whereas AA was converted into dehydroascorbic acid (DHAA). Consequently, an ALP activity-dependent RF response was achieved by coupling with the condensation reaction between OPD and the DHAA, which yields fluorescent 3-(1,2-dihydroxy ethyl) furo[3,4- b ] quinoxalin-1(3 H)-on with the maximum emission at 430 nm. Using the anti-STX polyclonal antibody and the commercial ALP-labelled secondary antibody as the recognition unit and signal transducing module, an ultrasensitive and accurate RF-ELISA for STX was developed with a detection limit of 3.2 pg/mL, which was 12-fold more sensitive than that of classic colorimetric ELISA. This work opened up new ways for ultrasensitive and accurate detection of STX and other analytes in food safety supervision. [Display omitted] • An ultrasensitive RF-ELISA was developed to detect saxitoxin. • CoOOH nanoflakes (nanozyme) was cascaded with ALP for amplifying the RF signal. • An H 2 O 2 -free RF sensing strategy was exploited. • The RF sensing platform exhibits good universality in food safety detection. [ABSTRACT FROM AUTHOR]

Antibody-based immunoassay is an important tool for detecting tetrodotoxin (TTX), a strong neurotoxic with high mortality rate. However, the traditional immunoassays always suffer from low sensitivity, high batch errors of the TTX conjugate and potential harmful to operators. In this work, we fabricated a monoclonal antibody (mAb) with good affinity and high selectivity against TTX, and selected a phage-displayed mimotope with specific binding to the anti-TTX mAb. Based on the mAb and mimotope, a non-toxic and dual-mode (electrochemical and colorimetric signal) immunosensor was developed for the highly efficient and sensitive detection of TTX. A biomimetic mineralized material encapsulated with anti-TTX mAb and HRP (e.g. HRP/anti-TTX mAb@ZIF-8) was used as the recognition element and signal probe. The developed electrochemical/colorimetric dual-mode sensing platform realized the simultaneous sensing of TTX: a wide detection range from 1.0 × 10-4 to 1.0 × 103 μg/mL, with a detection limit as low as 1.0 × 10-5 μg/mL by electrochemical analysis; a linear range from 1.05 × 10-3 - 3.8 × 10-1 μg/mL, accompanied by a detection limit of 1.83 × 10-4 μg/mL by colorimetric analysis based on a smart phone. To the best of our knowledge, we report for the first time on the development of electrochemical/colorimetric dual-mode sensing platform with non-toxic recognizing strategy for detecting TTX, which is highly desirable for detecting and monitoring toxins residue in food samples. [Display omitted] • A phage mimic epitope peptide was created for the non-toxic and environmentally friendly immunoassay technology. • The HRP/anti-TTX mAb@ZIF-8 nanocomposites were prepared as the nanoprobes of dual mode analysis. • We designed a novel dual-mode biosensing strategy for tetrodotoxin assay, which can be used in different scenarios. • The electrochemical signal is dependent on the electrochemical workstation and has high sensitivity. • The colorimetric signal is dependent on the designed mini program based on smart phone which is faster and more convenient. [ABSTRACT FROM AUTHOR]

Bongkrekic acid (BA) is a mitochondrial toxin that causes high mortality but is often mistakenly categorized as other food poisonings. The immunoassay of BA is still challenging since the specific antibody is unavailable. In this work, a monoclonal antibody specific to BA was first generated and a dual-modular immunosensor for on-site and laboratory detection was established. The antibody showed good affinity (Kd=0.33 μM) and sensitivity (IC 50 =17.9 ng/mL in ELISA) with negligible cross-reactivity with common mycotoxins. In dual-modular conditions, fluorescence assay (FA) was conducted based on the inner filter effect of carbon dots (CDs) and oxidized 3,3′,5,5′-tetramethylbenzidine (TMB), while the colorimetric assay (CA) was conducted using TMB2+-mediated rapid surface etching of gold nanostars (Au NSs). The proposed immunosensor showed good sensitivity and reproducibility to BA in food samples, with a limit of detection lower than 10 ng/mL and recovery ranging from 80.0% to 103.6%, which was in good consistence with that of standard LC-MS/MS. Overall, the proposed immunosensor is an ideal tool for screening BA contaminants in food with good sensitivity and high effectivity. [Display omitted] • We have first produced anti-bongkrekic acid (BA) monoclonal antibody. • A dual-modular immunosensor was established for the sensitive and specific detection of BA. • The proposed immunosensor can be used for on-site and laboratory detection of BA-contaminated food. [ABSTRACT FROM AUTHOR]

Herein, a ratiometric fluorescence (RF) enzyme-linked immunosorbent assay (RF-ELISA) for sensitive detection of ethyl carbamate (EC) was developed by introducing fluorescent silicon nanoparticles (Si NPs) into the chromogenic substrate system (o-phenylenediamine (OPD)/H 2 O 2 ) of a conventional horseradish peroxidase (HRP)-based ELISA platform to assemble a RF-based signal output system. For this system, the fluorescence of Si NPs at 440 nm (I 440 ) was acted as the reference signal which could be efficiently quenched by 2,3-diaminophenazine (DAP), the HRP-catalyzed oxidation product of OPD; Meanwhile, the fluorescence of DAP at 570 nm (I 570 ) was served as response signal. Therefore, variation in the amount of HRP labeled secondary antibody bound on the microplate which is associated with antibody-antigen recognition events in conventional HRP-based ELISA could be transferred into a more sensitive RF signal (I 570 /I 440 ). On the basis of monoclonal antibody (mAb) which could specifically recognize EC derivative, xanthyl ethyl carbamate (XEC), a Si NPs-based RF-ELISA for EC via a simple pre-analysis derivatization was developed. When detecting the EC content in red wine, this method exhibits a working range from 3.9 to 105.0 μg/L and a limit of detection (LOD) of 2.6 μg/L with excellent specificity, accuracy and reproducibility. The sensitivity is approximately 33-fold higher than that of traditional colorimetric ELISA. The proposed Si NPs-based RF-ELISA is not only highly suitable for screening EC in a large number of samples, but also provides a potential platform for high-throughput and sensitive determination of other analytes for food safety monitoring. [ABSTRACT FROM AUTHOR]

Progesterone (P4) is a kind of hormone that can cause neuropathic disturbances in humans when the concentration overpasses a certain degree. In this work, an electrochemical immunosensor capable of detecting P4 sensitively and selectively was developed. Thionine-graphene oxide (Thi-GO) composites with excellent biocompatibility were synthesized and coated to a clear glassy carbon electrode. P4 coating antigen (P4-OVA) was immobilized to the electrode, then sample as well as biotinylated antibody (biotin-P4 Ab) were added. The free P4 can compete with P4-OVA for binding to biotin-P4 Ab. After the further addition of streptavidin-HRP, H 2 O 2 was introduced to develop electrical signal for quantitative determination of P4. After careful optimization of assay conditions, the proposed immunosensor showed a linear range from 0.02 to 20ngmL −1 for P4 in milk samples. The averaged recoveries from spiked samples ranged from 84.0% to 102.0%, which correlated well with standard HPLC-MS/MS. The biosensor also showed good specificity, reproducibility and stability, indicating its potential application in monitoring of P4 in a simple and low cost manner. [ABSTRACT FROM AUTHOR]

The widespread occurrence of ethyl carbamate (EC, 89.09 Da), a group 2A carcinogen, in fermented foods and alcoholic beverages has raised worldwide public health concern. Immunoassay for EC is unavailable due to the simple and small structure of EC. In this work, an initial attempt to produce antibody specific for EC, by using 4-((ethoxycarbonyl)amino)butanoic acid as hapten, was made but failed. However, since EC can easily react with 9-xanthydrol to form xanthyl ethyl carbamate (XEC), two haptens based on XEC structure were designed and synthesized. Polyclonal antibody against XEC, instead of EC was obtained and then used to develop a competitive indirect ELISA for EC via a pre-analysis derivatization. After optimization, the ciELISA was applied in analyzing Chinese rice wine with detection limit of 166 μg/L, and negligible cross-reactivity with EC analogs. Recoveries of EC in fortified samples were from 84.4% to 100.9%, with coefficients of variation below 10%. Results for analysis of real samples by the ci-ELISA correlated well with that by reference method GC-MS, suggesting the good accuracy and reproducibility of the proposed method. This is the first report of an immunoassay capable of detecting EC, which is suitable for monitoring EC in a large amount of samples. [ABSTRACT FROM AUTHOR]

The aim of the investigation was to isolate lactic acid bacteria (LAB) from Chinese pickle, which could improve the quality of pickle by inoculation fermentation. In this study, three LAB were selected from pickle, based on 16S rDNA sequencing, which were named L. fermentum FM 8, L. sp FM 10, and L. plantarum FM 17, respectively. These strains were independently introduced in pickles during fermentation to investigate their effects on fermentation. Compared with naturally fermented pickle samples, pickle samples inoculated with L. fermentum FM 8 or L. plantarum FM 17 required less time for fermentation and had lower nitrite levels. After four kinds of pickle (without inoculation, inoculated with L. fermentum FM 8, inoculated with L. sp FM 10, inoculated with L. plantarum FM 17) were fermented at 25 °C for 15 days, these flavor-related components (organic acids, free amino acids, and volatile substances) were investigated. As results, partial least squares-discriminant analysis (PLS-DA) showed that samples of four groups could be divided into independent based on the flavor-related components, and 13 representative flavor-related compounds were selected characteristic with VIP (variable importance in projection) > 1. In addition, sensory evaluation showed that pickles inoculated with L. plantarum FM 17 had the highest overall acceptability scores. This study may help to develop strategies for reducing nitrite levels and improving the quality of pickles using L. plantarum FM 17 as a starter. • Three LAB strains were selected and identified from pickle. • The effects of different LABs on the physicochemical and flavor characteristics of pickle were investigated. • 13 representative flavor-related compounds were identified in the pickles of inoculating different LAB. [ABSTRACT FROM AUTHOR]

• An electrochemical immunosensor for parathion based on nanomaterial was prepared. • Nanofiber was favorable for electrochemical response compared to casting film. • The established sensor showed low limit detection of 2.26 pg/mL. • The sensor had good specificity and long-term stability. • The sensor was accurate to use in spiked food samples. For monitoring of the residual of parathion pesticide in food, herein, a sensitive and reliable electrochemical immunosensor based on cross-linked polyvinyl alcohol/citric acid nanofiber membrane (PVA/CA NFM) and horseradish peroxidase labeled anti-parathion nanobody was constructed. Firstly, the cross-linked PVA/CA NFM with extra-high surface area and uniform morphology was prepared and characterized. Then, the immunosensor was assembled and its analytical performances were evaluated. It exhibited high specificity and sensitivity to parathion with the liner range and limit of detection being 0.01–100 ng/mL and 2.26 pg/mL, respectively. Moreover, the biosensor kept almost 75% of its initial activity after regenerating 4 times, and remained 85% after 9 weeks of storage. Finally, the average recoveries from food samples were 96.20%–114.61% with the coefficient of variation being 1.06%–5.28%, which was correlate well with UPLC (R2 = 0.9964). Therefore, the sensor was demonstrated to be a feasible alternative for sensitive assay of parathion. [ABSTRACT FROM AUTHOR]

Fenpropathrin (FPT) is a typical pyrethroid pesticide that can cause chronic toxicity to humans. Herein, an anti-FPT monoclonal antibody (mAb) was elicited via a novel hapten synthesized by introducing a carboxyl-containing spacer arm in the cyclopropane moiety of FPT. Characterized by enzyme-linked immunosorbent assay (ELISA), the mAb exhibited high affinity and selectivity to FPT with a half-maximal inhibitory concentration of 31.05 μg/L and negligible cross-reactivities with analogs of pyrethroids. Based on the mAb, a fluorescence immunochromatographic assay (FICA) for FPT detection was firstly developed. The detection limit of the FICA is 0.012 mg/kg which is much lower than the maximum residue limit of FPT for food samples. The average recoveries of FPT from spiked food samples by the FICA were 85.0–105.0%, and the obtained results were in good agreement with those of gas chromatography-tandem mass spectrometry. Overall, this work provided a reliable tool suitable for the detection of FPT residue for large-scale samples in a rapid and cost-effective manner. [Display omitted] • A novel immunizing hapten against fenpropathrin (FPT) was synthesized. • A highly specific anti-FPT monoclonal antibody was produced. • A fluorescence immunochromatographic assay for FPT detection was firstly developed. [ABSTRACT FROM AUTHOR]

Biogenic amines (BAs) are of great concern as endogenous contaminants. In this study, the BA level and its formation in soy sauce were analyzed, and an efficient BAs reduction strategy was also explored via simple phytochemical addition. The results indicated that phenylethylamine (PHM), histamine (HM), tyramine (TYM) and putrescine (PUT) were the dominant BAs in soy sauce products, and the total BA levels were within the range 6.46 mg/L to 317.49 mg/L. In general, the total BA contents were low in soy sauces that had high amino nitrogen levels. Moreover, we found a good linear relationship between the HM and TYM contents in soy sauce products and fermented moromi. The content of BAs in the fermented moromi first increased, reaching a maximum content of 628.51 mg/L after 90 d of fermentation, then decreased. The inhibition effects of seven phytochemicals on BAs formation were tested. Quercetin showed a good result in BAs inhibition, and the contents of PUT and HM decreased were by 37.72% and 34.34%, respectively. Notably, quercetin had a negligible effect on BA degradation in the fermentation anaphase and on the quality of the soy sauce, indicating it is a promising additive for controlling BA levels in soy sauce. • The BAs level of 53 soy sauce were analyzed, and its formation was predicted otherwise analyzed. • Significant correlations between HM and TYM levels were found for both soy sauce products and fermented moromi. • Quercetin was found to be effective in reducing BAs during moromi fermentation. • Quercetin had a relatively limited effect on soy sauce quality after a long period of fermentation. [ABSTRACT FROM AUTHOR]

Multicolor immunosensor is a promising tool for on-site rapid analysis by naked eye without bulky instruments. Herein, a multicolor immunosensor employed a specific nanobody-alkaline phosphatase fusion protein (VHHjd8-ALP) for biosensing of fenitrothion was developed. After one-step indirect competitive immunoassay, the binding VHHjd8-ALP in microplate catalyzed ascorbyl-2-phosphate (AAP) into ascorbic acid, which propose dual readout including multicolor ratiometric visible immunoassay (MRVIA) and multicolor ratiometric fluoroimmunoassay (MRFIA). For MRVIA, K 3 [Fe(CN) 6 ] and Fe3+ was employed for multicolor generation. The substrate AAP can chelate with Fe3+ to form orange AAP-Fe3+ complex. When ALP catalyzed AAP into ascorbic acid, the latter can reduced K 3 [Fe(CN) 6 ] into K 4 [Fe(CN) 6 ], which reacted with Fe3+ to produced Prussian blue via self-assembly. A visible color transition from orange to blue against fenitrothion was obtained. For MRFIA, the generated ascorbic acid etched MnO 2 nanosheet to control the concentration of Na 2 SO 3 , which can convert 9-anthraldehyde into sulfuretted anthracene accompanied by a fluorescent color transition from green to blue. These two methods showed visible multicolor transition against fenitrothion for naked-eye analysis. The recovery and blind samples test verified good accuracy and practicability, which can be used for rapid screening of fenitrothion by a naked-eye semiquantitative analysis mode. [Display omitted] • Multicolor immunoassays were achieved without precious-metal materials. • Color regulation relies on ratiometric changing of dual signals. • The VHHjd8-ALP-based strategy can develop a dual multicolor immunosensor. • They can be used for semiquantitative detection without complex apparatus. [ABSTRACT FROM AUTHOR]

• Monoclonal antibody specific for tyramine was prepared based on a new hapten design. • Alkaline phosphatase enabled the growth of gold nanostars for multicolor generation. • A multicolor colorimetric immunoassay for tyramine was developed. • Smartphone was used for quantitative detection of tyramine. In this work, a specific monoclonal antibody against tyramine was produced based on a new hapten design. Then, we developed a high-resolution multicolor colorimetric immunoassay for tyramine based on this antibody by integrating enzyme-induced multicolor generation with smartphone-assistant signal readout. The multicolor generation is due to the shift of the local surface plasmon resonance band of gold nanostructure controlled by alkaline phosphatase-induced the growth of gold nanostars. Quantitative detection of tyramine was achieved via analyzing the red/blue channel values of assay solution's image taken by a smartphone with the support of a color recognizer application. The limit of detection of this immunoassay for tyramine detection in beef, pork and yoghurt was 19.7 mg/kg or L. The average recoveries were between 83 % and 103 %., and the results were validated by high performance liquid chromatography to be reliable. Overall, this developed immunoassay provides a promising platform for on-site detection of tyramine. [ABSTRACT FROM AUTHOR]

19-nortestosterone (19-NT), being regarded as the residual marker of banned synthetic steroid hormone nandrolone phenylpropionate, could cause adverse effects when consumed by human. To ensure food safety and minimize 19-NT toxicity, herein, an innovative electrochemical immunosensor for detection of 19-NT was constructed based on the modified polyvinyl alcohol/polyacrylic acid (PVA/PAA) nanofiber mat (NFM). The detection was achieved via a direct competition for binding to horse radish peroxidase-tagged anti-19-NT nanobody between free 19-NT and the 19-NT-ovalbumin covalently immobilized onto the NFM, and the amperometric response of immunosensor was analyzed using cyclic voltammetry. Under the optimal preparation conditions, the PVA/PAA NFM with appropriate hydrophilicity and ultra-high surface was obtained and characterized, and its electrochemical performance exhibited a 20-times increased response compared to the PVA/PAA casting membrane. The established immunosensor possessed high sensitivity towards 19-NT with a detection limit of 2.14 pg/mL, a 46-fold times lower compared to the traditional ic-ELISA of pure anti-19-NT nanobody. Recovery rates from the spiked animal urine samples ranged from 97.09 % to 117.32 %. Moreover, the sensor showed good reproducibility and stability over 6 weeks, suggesting that the nanofiber-based biosensor is a promising alternative for the fast and sensitive determination of 19-NT. [Display omitted] • A nanobody and PVA/PAA nanofibers based immunosensor for 19-NT was prepared. • The established biosensor possessed a detection limit of 2.14 pg/mL. • The special structure of nanofibers was favorable for the enhanced response. • The biosensor showed good reproducibility and stability over 6 weeks. [ABSTRACT FROM AUTHOR]

A VHH antibody (or nanobody) is the antigen binding fragment of heavy chain only antibodies. Discovered nearly 25 years ago, they have been investigated for their use in clinical therapeutics and immunodiagnostics, and more recently for environmental monitoring applications. A new and valuable immunoreagent for the analysis of small molecular weight environmental chemicals, VHH will overcome many pitfalls encountered with conventional reagents. In the work so far, VHH antibodies often perform comparably to conventional antibodies for small molecule analysis, are amenable to numerous genetic engineering techniques, and show ease of adaption to other immunodiagnostic platforms for use in environmental monitoring. Recent reviews cover the structure and production of VHH antibodies as well as their use in clinical settings. However, no report focuses on the use of these VHH antibodies to detect small environmental chemicals (MW < 1500 Da). This review article summarizes the efforts made to produce VHHs to various environmental targets, compares the VHH-based assays with conventional antibody assays, and discusses the advantages and limitations in developing these new antibody reagents particularly to small molecule targets. [ABSTRACT FROM AUTHOR]

Development of accurate and reliable FRET-based assays is of great significance to establish efficient warning-early mechanisms for reporting heavy metal pollution and safeguarding food safety. This review concentrates on the advances of various FRET-based assays toward heavy metals in food and agriculture-related matrices, and profiles the current and future trends, including future commercial point-of-care testing. [Display omitted] • FRET-based assay is a promising technique for monitoring heavy metals to safeguard food safety. • Summarizing the FRET principle in developing efficient assays toward heavy metals for food safety. • Analyzing the progress of FRET-based assays for heavy metals in food and agriculture-related matrices. • Pointing out the challenges and perspectives in FRET-based assays toward heavy metals for food safety. As one of the serious threats to food safety and public health, heavy metal contamination in food and agriculture-related matrices has aroused serious concern for the public and needs to be solved urgently. In this regard, it is important to focus on developing ingenious assays for facile, reliable, efficient, and accurate reporting the residual levels of heavy metals in food and agriculture-related matrices. Recently, with the prosperous progress of fluorescence assays, fluorescence resonance energy transfer (FRET)-based assays have been emerging as one of the most promising analytical tools to recognize and quantify the fouling of heavy metals in food and agriculture-related matrices, which exhibits a simple, rapid, cost-effective, reliable, stable, sensitive, selective, and real-time way. Regarding the vast endeavors that have been contributed in this field up to now, we here summarize the recent advances of FRET-based innovative assays for reporting the contamination of heavy metals (e.g. , Hg, Cu, Pb, Fe, Ag, Cd, Cr, As, U, and their mixture) in complicated food and agriculture-related matrices, point out the unavoidable challenges, and propose the future perspectives. This review might give important insights for developing effective warning-early mechanisms, management strategies, and commercial FRET-based point-of-care assays toward heavy metal contamination in food and agriculture-related matrices, safeguarding food safety and public health. [ABSTRACT FROM AUTHOR]

Fenitrothion (FN) residue in food is a serious threat to public health. Consequently, a sensitive, cost-effective, and convenient immunoassay for FN urgently needs to be fabricated to safeguard human health. Herein, a nanobody-alkaline phosphatase fusion protein (Nb-ALP)-based fluorescent ELISA using red emissive carbon dots (r-CDs) anchored cobalt oxyhydroxide nanosheet (CoOOH NS) composite was developed for detecting FN. Briefly, a Nb-ALP was obtained by autoinduction expression and employed as a recognition, signal transduction, and amplification element. As the fluorescence signal source, r-CDs were assembled with CoOOH NS to yield the r-CDs@CoOOH NS composite, leading to the fluorescence quenching of r-CDs via Förster resonance energy transfer (FRET). After competitive immunoreaction, the Nb-ALP bounded to the immobilized antigen can mediate the production of ascorbic acid, which can reduce the CoOOH NS to Co2+, breaking the FRET between r-CDs and CoOOH NS, accompanied by the fluorescence recovery of r-CDs. This fluorescent ELISA is highly sensitive to FN with a detection limit of 0.14 ng mL−1, which is 25-fold lower than that of conventional colorimetric ELISAs. The recovery test of food samples and the validation by GC−MS/MS further demonstrated the proposed assay was an ideal tool for detecting FN. [Display omitted] • Nanobody-alkaline phosphatase (Nb-ALP) against fenitrothion was prepared. • The red-emissive carbon dots@cobalt oxyhydroxide nanocomposite was prepared. • The nanocomposites as a signaling element have been used for fabricating immunoassay. • A highly sensitive fluorescent ELISA for fenitrothion was developed. [ABSTRACT FROM AUTHOR]

As an opportunistic pathogen, Bacillus cereus (B. cereus) has caused increasing emetic and diarrheal food poisoning, even fulminant hepatic failure and death case. Herein, a mimetic oxidase-mediated ratiometric fluorescence enzyme-linked immunosorbent assay (ELISA) was developed to detect B. cereus. In this system, 3D MnO 2 -Au nanoflowers with layered crystalline structure can oxidize o -phenylenediamine (OPD) to generate a fluorescence peak at 570 nm (I 570 , response signal), while blue carbon quantum dots (bCDs) display a fluorescence peak at 455 nm (I 455 , reference signal). Under the effect of fluorescence resonance energy transfer (FRET), the response signal increased while the reference signal was weakened. By using MnO 2 -Au as the mimetic oxidase to replace the horseradish peroxidase and associate with antibody in traditional ELISA, a linear relationship was established between the ratiometric fluorescence signal (I 570 /I 455) and the logarithm of B. cereus concentrations in the range from 1.7 × 102 to 3.3 × 106 CFU/mL. Comparing with conventional sandwich ELISA, the detection time was shortened by 43 min and the sensitivity was improved by 5-folds, indicating that the proposed ratiometric immunoassay holds great potential as a rapid and convenient tool for sensitive screening of B. cereus. [Display omitted] • A ratiometric fluorescent immunoassay based on FRET was developed to detect B. cereus. • MnO 2 -Au nanoflowers was used as mimic oxidase to anchor antibody. • A linear range from 1.7 × 102 to 3.3 × 106 CFU/mL B. cereus was realized. • Bacillus cereus in milk was successfully detected with satisfactory recoveries. [ABSTRACT FROM AUTHOR]

Histamine (HA) is one of the key causative agents associated with allergies and food poisoning. The accurate and convenient detection of HA is highly required to avert HA toxicity and ensure food safety. Herein, a multicolorimetric and fluorometric dual-readout immunosensor for HA detection was developed based on an alkaline phosphatase (ALP) enabled multicolor change reaction and fluorescence quenching of carbon dots (CDs) resulting from the metallization of gold nanorods (Au NRs). In this immunosensor, ALP is employed as labeling enzyme which can efficiently catalyze the hydrolysis of ascorbic acid 2-phosphate into ascorbic acid (AA). Then, the resultant AA can reduce Ag+ into silver monomer, and a silver shell is deposited on the surface of Au NRs to form Au/Ag core-shell nanorods (Au NRs@Ag). This leads to the blue-shift of the longitudinal local surface plasmon resonance peak of Au NRs and a vivid multicolor variation. Meanwhile, the fluorescence of CDs can be gradually quenched via inner-filter effect by the resultant Au NRs@Ag. Multicolorimetric assay allows a semiquantitative detection with a visible detection limit of 0.25 mg/L, and fluorometric assay provides a sensitive and accurate quantitative detection with a detection limit of 0.08 mg/L. The immunosensor not only fulfills the reliable and accurate detection requirements but also fits different testing needs for both laboratory and on-site detection. • We developed a dual-mode sensor for rapid and accurate histamine detection in foods. • Tunable metallization of gold nanorods was used for multicolorimetric sensing. • Samples with excess histamine can be easily discriminated with the naked eye. • A carbon dots was employed as fluorescent signal source for fluorescent sensing. • The carbon dots quenching mechanism was confirmed to be inner filter effect. [ABSTRACT FROM AUTHOR]

Rapid and quantitative detection of paraquat is crucial because of its high toxicity. Here, we developed an ultrasensitive time-resolved fluorescence immunochromatographic assay (TRFICA) strip based on our synthesized variable domain of heavy chain antibody (VHH, also called Nanobody) for paraquat detection. Briefly, the specific immunogen selected from six designed antigens was employed to immunize alpaca, and a high-efficiency capacity of 1.6 × 1013 pfu mL−1 phage display nanobody library was established for biopanning against paraquat. The selected nanobody exhibited high sensitivity (limit of detection (LOD) was 0.0090 ng mL−1 and IC 50 was 0.0588 ng mL−1 in buffer) and stability to high temperatures and denaturants. The molecular docking results indicated that the π-π, cation-π, and hydrogen bond interactions between paraquat and the pocket-like structures of complementarity-determining regions (CDRs) in VHH played a critical role in the antibody-paraquat recognition, competition, and affinity processes. The constructed TRFICA recognized paraquat through a quantitative analysis using the strip reader, and showed no cross-reactivity with other herbicides, and a semi-quantitative analysis using the naked eye. Notably, the potential practical applications of the TRFICA evaluated by performing a quantitative analysis of paraquat in food samples (vegetables, fruits, and grain products) and biological samples (blood and urine) showed a recovery rate range between 76.7% and 133.3% with inter-assay coefficient variation lower than 18.5%. The nanobody from phage display libraries was effective for small molecule recognition and detection, and it is a vital tool for immunoassay. • The binding mode between the nanobody and paraquat was analysed through molecular simulation. •The ultrasensitive ICA strip was developed by nanobody-based time-resolved fluorescent microspheres as signal probe. •The test results of the developed TRFICA in real samples showed a good consistence with those of UPLC-MS/MS. [ABSTRACT FROM AUTHOR]

• PBNPs was proved to have high catalytic activity for H 2 O 2 -inudced oxidation of OPD. • A novel PBNPs-based ratiometric fluorescence immunoassay for histamine was developed. • The quenching mechanism of CDs was confirmed to be the inner filter effect via oxOPD. Herein, a nanozyme-mediated ratiometric fluorescence immunoassay for histamine (HA) has been developed. Prussian blue nanoparticles (PBNPs) with outstanding peroxidase-like activity were labelled with goat anti-mouse IgG via a facile electrostatic adsorption to yield the nanozyme-antibody conjugate which acted as a bridge to link the ratiometric fluorescence readout with HA concentration. As substrate, o-phenylenediamine (OPD) was oxidized into 2,3-diaminophenazine (oxOPD) by H 2 O 2 under the catalysis of PBNPs, producing a novel emission at 570 nm and quenching the fluorescence of carbon dots (CDs) at 450 nm simultaneously. Under optimal conditions, the ratio of fluorescence intensity at 570 nm and 450 nm (I 570 /I 450) linearly correlated with HA concentration ranging from 1.6 ng/mL to 125 μg/mL, with a detection limit (LOD) of 1.2 ng/mL. In addition, analytical performances including specificity, accuracy and applicability were evaluated, which revealed that this ratiometric fluorescence immunoassay affords an effective platform for sensitive and accurate detection of HA. [ABSTRACT FROM AUTHOR]

The excessive use of carbaryl has resulted in the risk of its exposure. In this study, we isolated six nanobodies (Nbs) from a camelid phage display library against the biomarker of carbaryl, 1-naphthol (1-NAP). Owing to its characteristics of easy genetic modifications, we produced a nanobody-alkaline phosphatase (Nb-CC4-ALP) fusion protein with good stability. A dual-emission system based ratiometric fluoroimmunoassay (RFIA) for quick and highly sensitive determination of 1-NAP was developed. Silicon nanoparticles (SiNPs) was used as an internal reference and for aggregation-induced emission enhancement (AIEE) of gold nanoclusters (AuNCs), while AuNCs could be quenched by MnO 2 via oxidation. In the presence of ALP, ascorbic acid phosphate (AAP) can be transformed into ascorbic acid (AA), the later can etch MnO 2 to recover the fluorescence of the AuNCs. Based on optimal conditions, the proposed assay showed 220-fold sensitivity improvement in comparison with conventional monoclonal antibody-based ELISA. The recovery test of urine samples and the validation by standard HPLC-FLD demonstrated the proposed assay was an ideal tool for screening 1-NAP and provided technical support for the monitoring of carbaryl exposure. [Display omitted] • Nanobody-alkaline phosphatase (Nb-CC4-ALP) against 1-NAP was prepared. • A dual-emission fluorescent system were constructed for Nb-CC4-ALP response. • The developed RFIA showed superior anti-interference ability. • The RFIA showed excellent sensitivity to 1-NAP. [ABSTRACT FROM AUTHOR]

A Pichia pastoris (P. pastoris) cell surface display system of Bombyx mori acetylcholinesterase (BmAChE) was constructed and its bioactivity was studied. The modified Bombyx mori acetylcholinesterase gene (bmace) was fused with the anchor protein (AGα1) from Saccharomyces cerevisiae and transformed into P. pastoris strain GS115. The recombinant strain harboring the fusion gene bmace-AGα1 was induced to display BmAChE on the P. pastoris cell surface. Fluorescence microscopy and flow cytometry assays revealed that the BmAChE was successfully displayed on the cell surface of P. pastoris GS115. The enzyme activity of the displayed BmAChE was detected by the Ellman method at 787.7 U/g (wet cell weight). In addition, bioactivity of the displayed BmAChE was verified by inhibition tests conducted with eserine, and with carbamate and organophosphorus pesticides. The displayed BmAChE had an IC50 of 4.17×10−8 M and was highly sensitive to eserine and five carbamate pesticides, as well as seven organophosphorus pesticides. Results suggest that the displayed BmAChE had good bioactivity. [ABSTRACT FROM AUTHOR]

Carbamate pesticides (CPs) are the most used pesticides in agricultural production and pest control. In this study, carbofuran, isoprocarb and carbaryl were employed as models, and a general hapten strategy based on carbamate moiety recognition was proposed. Molecular modeling of the three-dimensional (3D) structure and surface electrostatic potential of the CPs indicated that the amide group formed by conjugation significantly influenced recognition by antibodies. The proposed strategy was used to obtain three sensitive and specific monoclonal antibodies (mAbs) with IC 50 values of 1.4 ng/mL, 8.4 ng/mL and 13.8 ng/mL for carbofuran, isoprocarb and carbaryl, respectively. Negligible cross-reactivity (%) with analogs was observed, except for fenobucarb (84.6%) for isoprocarb. The obtained antibodies were used to develop an immunochromatographic assay (ICA) to simultaneously and quantitatively detect the three CPs. A strip reader was used to determine the limits of quantitation (LOQs) as 0.05 ng/mL (carbofuran), 31.3 ng/mL (isoprocarb) and 31.3 ng/mL (carbaryl). The recoveries of cucumber and Chinese cabbage samples ranged from 76% to 111%, with CVs from 1.3% to 10.6%, indicating good potential for the rapid simultaneous detection of multiple pesticide residues in a large batch of samples. [Display omitted] • General hapten design strategy for carbamate pesticides was provided. • Good monoclonal antibodies for carbofuran, isoprocarb and carbaryl were raised. • Relationship between antibody and haptens were studied by molecular modeling. • Immunochromatographic assay for simultaneous determination was developed. [ABSTRACT FROM AUTHOR]

• Ethyl carbamate formation during thermal process of soy sauce were studied. • Ornithine and quercetin were found to be effective for reducing ethyl carbamate. • The possible mechanisms were explained. • No remarkable difference in volatile compounds profile and color of soy sauce were found. Ethyl carbamate (EC), a genotoxic and carcinogenic compound in soy sauce accumulated during thermal processes, has raised public health concern for its multipoint potential carcinogenic risk to human. In this work, based on the analysis of EC accumulation during thermal processes of soy sauce, ornithine and quercetin were added before thermal processes to reduce EC accumulation. A reduction rate of 23.7–63.8% in simulated solution was founded. Kinetic studies indicated that ornithine was a byproduct of alcoholysis reaction when EC formed, while quercetin could compete with the precursor ethanol and react with carbamyl compounds, which therefore prevented EC accumulation. A maximum of 47.2% decrease of EC in soy sauce was achieved, and no remarkable changes in volatile compounds profile and color of soy sauce were found. In conclusion, the addition of quercetin and ornithine before thermal processes may be preferable for the controlling of EC content in soy sauce. [ABSTRACT FROM AUTHOR]

• Two haptens against xanthyl acrylamide (XAA) were designed and synthesized for the first time. • A specific and high-affinity polyclonal antibody against XAA was raised and characterized. • A green-emission carbon dots was employed as the fluorescent signal probe to improve the assay sensitivity. • A highly sensitive fluorescence immunoassay was developed for the fast detection of acrylamide in foods. The far-ranging occurrence of acrylamide (AA), a Group 2A carcinogen, in extensively consumed processed foodstuffs has aroused worldwide public health concern, and heightened the need for rapid and reliable detection technologies. Current immunoassays for AA are mainly based on antibodies against mercaptobenzoic acid (MBA) derivatized AA, and thus require a relatively complicated pre-analysis sample derivatization using MBA (heating > 50 °C, time>1 h), which limits the analysis efficiency. In this work, two haptens against xanthyl acrylamide (XAA) were synthesized, and a specific and high-affinity polyclonal antibody against XAA (anti-XAA pAb) was obtained. By virtue of this antibody, a fluorescence immunoassay for quantification of acrylamide with a simple sample derivatization by 9-xanthydrol (ambient temperature, 30 min) was developed via introducing the fluorescent signal of carbon dots (CDs) through the facile inner-filter eff ;ect (IFE) strategy. This fluorescence immunoassay displayed a sensitive and specific response to AA with a detection limit of 0.16 μg/L, which was lower than the legal limit in drinking water (0.5 μg/L) set by WHO. Recovery test and method validation by HPLC-MS/MS demonstrated its good accuracy and reliability, suggesting that this fluorescence immunoassay can be a potentially effective tool for the supervision of AA contamination in foods. [ABSTRACT FROM AUTHOR]

Investigating organic carriers' utilization efficiency and bioactivity within organic-inorganic hybrid nanoflowers is critical to constructing sensitive immunosensors. Nevertheless, the sensitivity of immunosensors is interactively regulated by different classes of biomolecules such as antibodies and enzymes. In this work, we introduced a new alkaline phosphatase-antibody-CaHPO 4 hybrid nanoflowers (AAHNFs) microreactor based colorimetric immunoprobe. This system integrates a biometric unit (antibody) with a signal amplification element (enzyme) through the biomineralization process. Specifically, the critical factors affecting antibody recognition activity in the formation mechanism of AAHNFs are investigated. The designed AAHNFs retain antibody recognition ability with enhanced protection for encapsulated proteins against high temperature, organic solvents, and long-term storage, facilitating the selective construction of lock structures against antigens. Additionally, a colorimetric immunosensor based on AAHNFs was developed. After ascorbic acid 2-phosphate hydrolysis by alkaline phosphatase (ALP), the generated ascorbic acid decomposes I 2 to I - , inducing the localized surface plasmon resonance in the silver nanoplate, which is effectively tuned through shape conversion to develop the sensor. Further, a 3D-printed portable device is fabricated, integrated with a smartphone sensing platform, and applied to the data of collection and analysis. Notably, the immunosensor exhibits improved analytical performance with a 0.1-6.25 ng·mL -1 detection range and a 0.06 ng·mL -1 detection limit for quantitative saxitoxin (STX) analysis. The average recoveries of STX in real samples ranged from 85.9% to 105.9%. This study presents a more in-depth investigation of the recognition element performance, providing insights for improved antibody performance in practical applications.

Profenofos (PFF) is a commonly used organophosphorus insecticide that requires strict monitoring due to its potential environmental, ecological, and human health risks originating from residues in soil and water systems, as well as accumulation in crops. In this study, a novel monoclonal antibody (mAb) targeting PFF was prepared for the first time and investigated the recognition mechanism through molecular simulation. Subsequently, a mAb-based colloidal gold immunochromatographic assay (GICA) was developed for the rapid screening of PFF in fruit and vegetable samples. The mAb exhibited an IC 50 value of 12.9 ng/mL, and limit of detection (LOD) of 4.6 ng/mL, respectively in indirect competitive immunosorbent enzyme-linked immunosorbent assay (ic-ELISA). After optimization, the developed GICA exhibited a visual limit of detection (vLOD) of 20 ng/mL and a quantitative of detection (qLOD) of 5.2 ng/mL, with a linear range from 10.0 to 83.8 ng/mL. Good correlation was observed between the results of GICA and standard Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) in matrix and recovery test. The developed GICA can be used for rapid sample detection within 15 minutes, which is an excellent tool for screening PFF in foods and environmental samples., Competing Interests: Declaration of Competing Interest ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2024. Published by Elsevier Ltd.)

Bacillus cereus ( B. cereus ) is a foodborne pathogen that can produce tripartite enterotoxins, which can cause a variety of diseases after infection. It is critical to rapidly and accurately detect strains with enteropathogenic potential to safeguard human health. In this study, a dual-signal visualized detection platform with fluorescence assay and paper-based lateral flow assay (LFA) based on recombinase polymerase amplification (RPA), CRISPR/Cas12a system, and self-developed CRISPR nucleic acid test strips was constructed for enterotoxigenic B. cereus . The genes that encode two tripartite enterotoxins─ nheA , nheB , and nheC for nonhemolytic enterotoxin and hblA , hblC , and hblD for hemolysin BL─were utilized as detection targets. The platform was capable of detecting six enterotoxin genes at the same genomic DNA level. The limits of detection for each gene were 10 -3 ng/μL in fluorescence assay and 10 -4 ng/μL in LFA. Furthermore, 10 1 -10 2 CFU/mL of B. cereus in pure culture was detected. Additionally, a smartphone miniprogram could assist in evaluating the results in LFA. The platform demonstrated good utility by detecting B. cereus in food samples, including milk and rice. The results indicate that our RPA-CRISPR/Cas12a dual-signal visualized detection platform can quickly and easily detect B. cereus with three-component enterotoxin-producing potentials. The whole analytic process took less than 60 min without complex operation or expensive equipment.

Food-borne biotoxins from microbes, plants, or animals contaminate unclean, spoiled, and rotten foods, posing significant health risks. Neutralizing such toxins is vital for human health, especially after food poisoning. Nanobodies (Nbs), a type of single-domain antibodies derived from the genetic cloning of a variable domain of heavy chain antibodies (VHHs) in camels, offer unique advantages in toxin neutralization. Their small size, high stability, and precise binding enable effective neutralization. The use of Nbs in neutralizing food-borne biotoxins offers numerous benefits, and their genetic malleability allows tailored optimization for diverse toxins. As nanotechnology continues to evolve and improve, Nbs are poised to become increasingly efficient and safer tools for toxin neutralization, playing a pivotal role in safeguarding human health and environmental safety. This review not only highlights the efficacy of these agents in neutralizing toxins but also proposes innovative solutions to address their current challenges. It lays a solid foundation for their further development in this crucial field and propels their commercial application, thereby contributing significantly to advancements in this domain.

Emetic Bacillus cereus ( B. cereus ), which can cause emetic food poisoning and in some cases even fulminant liver failure and death, has aroused widespread concern. Herein, a universal and naked-eye diagnostic platform for emetic B. cereus based on recombinase polymerase amplification (RPA)-assisted CRISPR/Cas12a was developed by targeting the cereulide synthetase biosynthetic gene ( ces B). The diagnostic platform enabled one-pot detection by adding components at the bottom and cap of the tube separately. The visual limit of detection of RPA-CRISPR/Cas12a for gDNA and cells of emetic B. cereus was 10 -2 ng μL -1 and 10 2 CFU mL -1 , respectively. Meanwhile, it maintained the same sensitivity in the rice, milk, and cooked meat samples even if the gDNA was extracted by simple boiling. The whole detection process can be finished within 40 min, and the single cell of emetic B. cereus was able to be recognized through enrichment for 2-5 h. The good specificity, high sensitivity, rapidity, and simplicity of the RPA-assisted CRISPR/Cas12a diagnostic platform made it serve as a potential tool for the on-site detection of emetic B. cereus in food matrices. In addition, the RPA-assisted CRISPR/Cas12a assay is the first application in emetic B. cereus detection.

Trimethoprim (TMP), functioning as a synergistic antibacterial agent, is utilized in diagnosing and treating diseases affecting livestock and poultry. Human consumption of the medication indirectly may lead to its drug accumulation in the body and increase drug resistance due to its prolonged metabolic duration in livestock and poultry, presenting significant health hazards. Most reported immunoassay techniques, such as ELISA and immunochromatographic assay (ICA), find it challenging to achieve the dual advantages of high sensitivity, simplicity of operation, and a wide detection range. Consequently, an open droplet microchannel-based magnetosensor for immunofluorometric assay (OMM-IFA) of trimethoprim was created, featuring a gel imager to provide a signal output derived from the highly specific antibody (Ab) targeting trimethoprim. The method exhibited high sensitivity in chicken and pork samples, with LODs of 0.300 and 0.017 ng/mL, respectively, and a wide linear range, covering trimethoprim's total maximum residue limits (MRLs). Additionally, the spiked recoveries in chicken and pork specimens varied between 81.6% and 107.9%, maintaining an acceptable variation coefficient below 15%, aligning well with the findings from the ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technique. The developed method achieved a much wider linear range of about 5 orders of magnitude of 10 -2 -10 3 levels with grayscale signals as the output signal, which exhibited high sensitivity, excellent applicability and simple operability based on magnetic automation.

In this study, three eugenol fragment-containing haptens were synthesized, and a monoclonal antibody (mAb) selective for five commonly-found eugenol compounds (EUGs, i.e., eugenol, isoeugenol, methyl eugenol, methyl isoeugenol, and acetyl isoeugenol) was obtained. Based on this mAb, a broad-spectrum indirect competitive ELISA for high-throughput detection of five EUGs was developed. The detection limits for eugenol, isoeugenol, methyl eugenol, methyl isoeugenol and acetyl isoeugenol in both tilapia and shrimp samples were 25.3/ 50.6 μg/kg, 0.075/0.15 μg/kg, 0.48/0.96 μg/kg, 0.16/0.32 μg/kg, and 18.16/36.32 μg/kg, respectively. The recoveries for five EUGs ranged from 80.4 to 114.0 % with a coefficient of variation less than 11.5 %. Moreover, homology modelling and molecular docking were conducted to elucidate the interactions mechanism of mAb-EUGs. The work provides a promising tool for high-throughput screening of EUGs in aquatic products, which can serve as a benchmark for designing haptens and developing immunoassays for other small molecules., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Gizzerosine is responsible for gizzard erosion and black vomit, owing to excessive gastric acid secretion in poultry. It is a biogenic amine that forms during feed processing. Gizzerosine, a derivative of histamine, is a serious threat to animal feed safety and poultry production because it is more potent after ingestion and more harmful to poultry than histamine. The difficulty of obtaining gizzerosine and the lack of simple, rapid, and sensitive in vitro detection techniques have hindered studies on the effects of gizzerosine on gizzard health and poultry production. In this review, we evaluated the natural formation and the chemical synthesis methods of gizzerosine and introduced seven detection methods and their principles for analyzing gizzerosine. This review summarizes the issues of gizzerosine research and suggests methods for the future development of gizzerosine detection methods.

The simultaneous determination of carbaryl and its metabolite 1-naphthol is essential for risk assessment of pesticide exposure in agricultural and environmental samples. Herein, several bispecific nanobodies (BsNbs) with different lengths of hydrophilic linkers and junction sites were prepared and characterized for the simultaneous recognition of carbaryl and its metabolite 1-naphthol. It was found that the affinity of BsNbs to the analytes could be regulated by controlling linker length and linking terminal. Additionally, molecular simulation revealed that linker lengths affected the conformation of BsNbs, leading to alteration in sensitivity. The BsNb with G 4 S linker, named G 4 S-C-N-VHH, showing good thermal stability and sensitivity was used to develop a bispecific indirect competitive enzyme-linked immunosorbent assay (Bic-ELISA). The assay demonstrated a limit of detection of 0.8 ng/mL for carbaryl and 0.4 ng/mL for 1-naphthol in buffer system. Good recoveries from soil and rice samples were obtained, ranging from 80.0% to 112.7% (carbaryl) and 76.5%-110.8% (1-naphthol), respectively. Taken together, this study firstly provided a BsNb with high sensitivity and efficiency against environmental pesticide and its metabolite, and firstly used molecular dynamics simulation to explore the influence of linker on recognition. The results are valuable for the application of immunoassay with high efficiency in the fields of environment and agriculture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)