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Rapid and sensitive detection of pesticide is of significance to the field of food safety and human health, but it is still challenging due to interferents from complex food matrices. Herein, a superb golf-shaped Bi 2 Se 3 microparticles-based immunochromatographic strip (BS MPs-ICS) was constructed for ultrasensitive detection of acetamiprid (ATM). The novel immune signal tag demonstrated outstanding luminance, excellent biocompatibility, and high affinity with ATM (affinity constant was 3.874 ×107 M−1), which not only possessed a preeminent labeling efficiency but also significantly improved detection sensitivity. After optimization, the limit of detection (LOD) of the BS MPs-ICS was 8.780 pg/mL with an excellent linear relationship at the range of 0.010–6.000 ng/mL, which was approximately 62-fold lower than that of conventional gold nanoparticles-ICS (0.545 ng/mL), The BS MPs-ICS biosensor was well applied in apple and tomato samples with satisfactory recoveries of 83.823–99.223% (relative standard deviation < 1.739%). Therefore, the BS MPs-ICS could serve as a promising candidate for ATM detection in complicated samples and develop a new method in real-time monitoring. [Display omitted] • The BS MPs-based test strip is firstly fabricated for the sensitive ATM detection. • The sensor exhibits a low detection limit and specificity for ATM detection. • Advantages of BS MPs for monitoring pesticide residues are mentioned. • The future prospect of BS MPs-mAb probes in the immunochromatographic fields. [ABSTRACT FROM AUTHOR]

Ultrasensitive and facile detection of Acetamiprid (ACE) is of exceptional significance to assess the environmental and biological pollution. In this study, an advanced Bi semimetal/Zeolitic imidazolate frameworks hybrid material-based immunochromatographic strip (Bi/ZIF HM-ICS) sensor was developed for the sensitive detection of ACE. The novel Bi/ZIF HM was prepared through one-pot hydrothermal reduction of Bi nanoparticles on ZIF, which was selected as a signal tag taking advantages of its excellent color intensity, strong affinity with monoclonal antibodies (mAbs), and favorable biocompatibility. Bi/ZIF HM could not only improve the utilization efficiency of mAbs but also boost the sensing performance. Under optimal conditions, the limit of detection (LOD) of the Bi/ZIF HM-ICS was 4.68 pg/mL with the linear range from 0.01 ng/mL to 6 ng/mL, which was 98-fold lower than that of traditional gold nanoparticles-based ICS (0.457 ng/mL), and the recoveries of the Bi/ZIF HM-ICS ranged from 80.27% to 118.52% with the relative standard deviation (RSD) below 3.67% in pear, apple, tomato, and cucumber. Overall, the practical application of the Bi/ZIF HM-ICS in complicated samples was realized for detecting pesticide residue, and expanding its application scope in monitoring environment. [Display omitted] • The Bi semimetal-ZIF hybrid material based immunochromatographic strip was firstly developed for detection of acetamiprid. • The synthesized Bi/ZIF HM possessed excellent color intensity, remarkable monoclonal antibodies coupling efficiency. • The sensor showed a low limit of detection (4.68 pg/mL, 98-fold improvement) and specificity for ACE detection. • The Bi/ZIF HM-ICS in monitoring pesticide residue proves the satisfactory applicability and stability. [ABSTRACT FROM AUTHOR]

• A sensitive sensor that utilized oriented probe was developed to detect aflatoxin B 1. • The Fe 2 O 3 -antigen probe directionally connected antibodies and improved bioactivity. • The proposed strategy possessed a low detection limit and wide detection range. • Satisfactory analytical results in real foodstuffs showed the sensor's feasibility. One of the major concerns in the application of nanocarriers in biosensing is the impair of the recognition molecules bioactivity loaded on their surfaces due to harsh and laborious cross-linking and random orientation, resulting in unsatisfactory sensitivity. Herein, we proposed a novel immunochromatographic test strip (FNS-ag-DICTS) by taking advantage of the antigen (ag) modified Fe 2 O 3 nanostructures (FNSs) as new signal tags and goat anti-mouse IgG labeling on the detection line instead of ag, which was used for sensitive detection of aflatoxin B 1 (AFB 1). The fabricated FNS-ag can orientate the Fab region of monoclonal antibodies (mAbs), waiving the intrinsic limitations of traditional nanomaterials labeled mAbs. Under optimal conditions, FNS-ag-DICTS possessed excellent specificity and a wide detection range, with a visual limit of detection (vLOD) of 0.0125 ng mL−1. In addition, the biosensor successfully detected AFB 1 in peanut, green bean and corn, with an average recovery rate of 82.8–124.9%. [ABSTRACT FROM AUTHOR]

• A prussian blue nanocubes decomposition-assisted competitive sensor was developed. • With the dissolution of the nanocubes, a decreased T -line intensity was obtained. • The proposed sensor was highly sensitive and selective with a low detection limit. • Satisfactory analytical results in real samples suggests the sensor's applicability. A prussian blue nanocubes decomposition-assisted signal amplification strategy for competitive lateral flow immunoassay (PBNCD-SALFIA) was innovatively proposed to analyze aflatoxin B 1 (AFB 1) in foodstuffs. The signal was amplified on account of the PBNCs can degrade and fade under alkaline condition, which could weak the color of the test- and control-lines, thereby improving the sensitivity of the sensor. The strategy was technically-simple, just using NaOH as an amplifier can realize signal amplification in the competition assay. Under optimized conditions, the enhanced strip exhibited excellent specificity and sensitivity in AFB 1 monitoring with a detection limit of 23 pg/mL, which was approximately 4- and 8-folds lower than those of PBNCs-LFIA (90 pg/mL) and conventional gold nanoparticles-LFIA (175 pg/mL), respectively. Taking the advantage of the color-fading, this platform revealing the lowest detectable concentration of 0.184, 0.368 and 0.184 μg/kg for AFB 1 in corn, peanut and pumpkin seed within 58 min, separately, showing reliable results. [ABSTRACT FROM AUTHOR]

• Metal-polydopamine framework (MPF) based lateral flow assay (LFA) was developed. • MPF displayed excellent affinity with antibodies to detect tetracycline. • Assay performance of this LFA was 66-fold higher than that of traditional AuNP-LFA. • This work expands the application of MOFs as a novel label in immunoassays. Gold nanoparticles (AuNPs)-based lateral flow assay (LFA) enables a rapid detection of tetracycline (TET) in food samples but suffers from low sensitivity. Herein, metal-polydopamine framework (MPF), as a label, was employed to load monoclonal antibodies (mAbs) directly as the probe in LFA for highly sensitive sensing of TET. Combining zeolitic imidazolate framework (ZIF-67) and polydopamine (PDA), a stable MPF with large size, well water-dispersible, excellent affinity and optical properties was prepared through a versatile layer-by-layer assembly (LLA) strategy. Under optimized conditions, the biosensor (MPF-LFA) exhibited a great linear relationship in the range of 0.09–6 ng/mL and a detection limit of 0.045 ng/mL for TET detection, which was over 66-fold more sensitive than traditional AuNPs based LFA. Furthermore, the MPF-LFA was successfully applied to the screening of TET in fish, chicken, milk and shrimp samples with satisfied recoveries from 91% to 114%. [ABSTRACT FROM AUTHOR]

• The rhombic-like Al nanosupporter (RAlNS) based fluorescence immunochromatographic assay was constructed. • The synthesized RAlNS can label antibodies in one-step stirring, avoiding the use of the complex cross-linkers. • The sensor possessed high sensitivity and specificity for tetracycline (TET). • Significant recovery rates of TET detection in real samples demonstrates the sensor's applicability. Fluorescence-based lateral flow immunoassay (FLFIA) is a prospective technology in detecting tetracycline (TET). However, the existing fluorescent materials (FMs) often require cross-linkers to bind with antibodies (Abs) to form FLFIA FM-Ab probe, which complicates the modification process and may affect the fluorescence intensity of FMs. Herein, the rhombic-like Al nanosupporter (RAlNS) was prepared via a one-step hydrothermal method and used for designing fluorescence nanosupporter for FLFIA to detect TET in real samples. The RAlNS not only possessed excellent water stability, strong fluorescence intensity and favorable thermal stability, but also could adsorb Abs to obtain FMs-Ab probe by simple centrifugation. Under optimal conditions, the limit of detection (LOD) of RAlNS-FLFIA was 0.0516 ng/mL (n = 3), which was 18 times lower than traditional colloidal gold-based LFIA. Meanwhile, the proposed sensor also exhibited high specificity for TET against other antibiotics. Furthermore, the RAlNS-FLFIA was successfully applied to the detection of TET in beef, chicken, milk and honey samples, separately, which demonstrated a significant recovery of 80.40–112.05%. The novel RAlNS-FLFIA provided great potential for the detection of various analytes in food analysis. [ABSTRACT FROM AUTHOR]

• A sensitive biosensor that introduced MoS 2 as extraordinary probes was constructed to detect tetracycline. • Exfoliated nanosheets with large, middle, and small sizes and all exhibited excellent water-dispersibility and stability. • The versatile MoS 2 can label antibodies without the need for surfactant modification. • A very low limit of detection of 0.023 ng/mL was obtained for tetracycline detection. In this study, we report a simple approach for synthesizing three kinds of molybdenum disulfide (MoS 2) nanosheets with different sizes of large, middle, and small (which are defined as L -MoS 2 , M -MoS 2 and S -MoS 2) by an aqueous-phase exfoliation and differential-zone centrifugation (AE-DC) strategy, and for the first time explored the MoS 2 labeled antibodies (Abs) as probes for sensitive detection of tetracycline (TET) on lateral flow assays (LFAs). The hierarchical MoS 2 had uniform sizes (Average size: 366 ± 65.70 nm, 131 ± 24.39 nm and 55 ± 8.56 nm for L -MoS 2 , M -MoS 2 , and S -MoS 2 , respectively; thickness: 3 nm, 1 nm for and 0.5 nm for L -MoS 2 , M -MoS 2 and S -MoS 2 , respectively), and all exhibited excellent water-dispersibility and stability. Compared with M -MoS 2 and S -MoS 2 based LFAs, L -MoS 2 based LFA particularly displayed highly sensitive detection of TET due to the larger surface area and stronger color intensity. Under optimized experimental conditions, the developed L -MoS 2 -based immunosensor showed a great linear relationship over the range of 0.012–0.75 ng/mL in 15 min and a signal sensitivity up to 0.023 ng/mL for TET detection, which was at least 17-fold lower than traditional gold nanoparticles based LFA. The assay resulted in excellent specificity and reproducibility, and can be well-applied in milk, honey, and beef samples for monitoring TET. [ABSTRACT FROM AUTHOR]

• A microorganism@AuNPs based immunosensor was constructed for ochratoxin A detection. • The probe was fabricated by reacting microorganism with HAuCl 4 via biosorption and bioreduction. • Assay performance of this novel biosensor was 8-fold improved for OTA detection. • The approach exhibited high selectivity and real food sample testing. A simple and novel immunochromatographic assay (ICA) was developed for specific and sensitive determination of ochratoxin A (OTA) employing microorganism (MO) as reducers and carriers. In this work, microorganism loaded gold nanoparticles (MO@AuNPs) composites were synthesized by reacting Yeast/Lactobacillus (LAB) with HAuCl 4 via biosorption and subsequent bioreduction. The synthesis conditions (pH and reaction time) and main parameters (morphology, diameter and functional groups) of MO@AuNPs were investigated. Owing to the large sizes (about 2 μm) and high adsorption abilities of MO@AuNPs, the few antibodies were labeled, resulting a lower detection limit for ICA. After optimization, the linear detection of OTA using MO@AuNPs-based immunoassay ranged from 0.1 to 1.6 ng/mL, and the visual limit of detection (vLOD) was 0.1 ng/mL, which was nearly 8-fold lower than traditional AuNPs-ICA. Meanwhile, the proposed strategy also possessed high specificity for OTA against other mycotoxins. The applicability of the platform was successfully assessed through the detection of OTA in rice, corn, ginger and green bean samples. The results indicated that these creative sensing elements are promising alternatives and bring an innovative inspiration for biological detections. [ABSTRACT FROM AUTHOR]

• A novel, sensitive, and stable fluorescent sensor was developed for TET detection. • The synthesized MoS 2 NPs possessed superior solubility and strong blue fluorescence. • A low detection limit of 0.032 μM with good linear relationship was achieved. • This prominent technique could be applied in milk and bovine muscle samples. The wide use of tetracyclines (TCs) for prevention and therapy of animal diseases may result in excessive residues in animal products, which could pose serious risks to human health. A novel molybdenum disulfide nanoplates (MoS 2 NPs)-based fluorescent sensor for tetracycline (TET) is reported. The MoS 2 NPs, synthesized via a facile bottom-up hydrothermal route, showed blue fluorescence at 430 nm in aqueous solution. Interestingly, its fluorescence was quenched significantly upon addition of TET, which is mainly due to a combination of the inner filter effect and electron transfer. Thus, the MoS 2 NPs based fluorescence sensor was delineated for the detection of TET. The methodology here presented showed a low detection limit of 0.032 μM and satisfied recoveries from 88.46% to 108.62% in spiked milk, milk powder and bovine muscle samples. [ABSTRACT FROM AUTHOR]

Silicon-doped carbon quantum dots (Si-CQDs) were employed to fabricate a ratiometric fluorometric probe that shows high selectivity for hydroquinone (HQ). The Si-CQDs were prepared through hydrothermal treatment of N-[3-(trimethoxysilyl)propyl]-ethylenediamine. If HQ is oxidized in a solution of the Si-CQDs, 1,4-benzoquinone will be formed which quenches the blue fluorescence (with excitation/emission peaks at 360/435 nm) of the Si-CQDs. Simultaneously, intense green fluorescence (with a emission peak at 513 nm) appears, probably due to the formation of n-π clathrates or of a quinone imine between 1,4-benzoquinone and amino groups on the surface of the Si-CQDs. The ratio of the green and blue fluorescence can be applied to the determination of HQ with a 0.077 μM detection limit. The analytical range extends from 1 to 40 μM. [ABSTRACT FROM AUTHOR]

• The Sc nanocubes based immunoassay was developed for detection of imidacloprid. • The Sc nanocubes had large surface area, remarkable intensity and biocompatibility. • The sensor had a low limit of detection and specificity for imidacloprid detection. • Satisfactory analytical results in real samples suggested the sensor's applicability. In this work, a highly sensitive immunochromatographic test strip (ITS) based on Scandium-Tetrakis (4-carboxyphenyl) porphyrin (TCPP) metal–organic framework nanocubes (ScTMNs) was developed for ultrasensitive and facile visual determination of imidacloprid (IDP). TCPP as the porphyrin-based planar ligand and Sc3+ as the metal center were applied to form the ScTMNs via coordination chelation. Giving the credit to its excellent optical characteristics, strong affinity with monoclonal antibodies, and favorable biocompatibility, the ScTMNs was selected as a signal tag. Under optimized conditions, the ITS exhibited a great liner relationship in the range of 0.04–3 ng/mL and the detection limit was 0.04 ng/mL for the IDP detection. Additionally, IDP was successfully detected in tomatoes, millet, corn and carrot samples with satisfied recoveries. To the best of our knowledge, this is the first time that ScTMNs have been used in immunochromatography which are expected to have potential applications in detection of other substances. [ABSTRACT FROM AUTHOR]

• The MoO 3 /Co 3 O 4 heterostructure was formed via a hybrid electrochemical deposition strategy. • The synergistic effect of Co 3 O 4 and MoO 3 plays a predominant role in nitrite electrooxidation. • The MoO 3 /Co 3 O 4 /CC has been successfully used in food samples for nitrite detection. Considering excess nitrites are detrimental to the human body and environment, designing a rapid, sensitive, and real-time quantitative determination for nitrite is of great significance for environmental preservation and public health. In this paper, Co 3 O 4 nanoflowers coupled with ultrafine MoO 3 nanoparticles (MoO 3 /Co 3 O 4) are obtained via a hybrid electrochemical deposition strategy (HED). The as-designed MoO 3 /Co 3 O 4 /CC integrating electrode exhibits superior electrocatalytic properties towards nitrite oxidation, owing to the synergistic effect between MoO 3 and Co 3 O 4 caused by the heterostructure of MoO 3 /Co 3 O 4. The electrode achieved a low response time of 2 s, an excellent sensitivity of 1704.1 μA mM−1 cm−2, and a low limit of detection of 0.075 μM (S/N = 3). Furthermore, the electrode displays promise for nitrite detection in complex food such as water and sausages samples. Our study will provide a significant strategy for the application of bimetallic heterostructure to explore the design of sensing interfaces. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have attracted tremendous interest due to their promising applications, including electrocatalysis originating from their unique structural features. However, it remains a challenge to prepare COFs for p-nitrophenol (PNP) and o-nitrophenol (ONP) electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology with abundant active sites. Here, a facile ambient temperature synthesis of unique Fe 3 O 4 -based magnetic COFs nanosphere (Fe 3 O 4 @AT-COFs) with different surface morphologic structure is reported, which exhibits higher surface area, good water dispersity, long-term stability, excellent electrical conductivity and pre-concentration effect. The prepared Fe 3 O 4 @AT-COF-based electrochemical sensor is then directly employed for the simultaneous detection of PNP and ONP with a wide linear detection range of 10–3000 μM and low detection limits (LOD) of 0.2361 μM and 0.6568 μM, respectively. Meanwhile, the Fe 3 O 4 @AT-COF can be also well-applied in lake and tap water for monitoring PNP and ONP with outstanding sensitivity and reliability, which is expect to be a high-efficient electrocatalyst with great promise for signal amplification of electrochemical sensing. Image 1 • Facile synthesis of Fe 3 O 4 -based magnetic COFs with different surface morphologic structure. • COFs as the enrichment carriers of Fe 3 O 4 were employed for amplifying electrochemical sensing signals. • Fe 3 O 4 plays a dual role in magnetic attraction with the electrode and synergistic catalysis effect with COFs. • A sensitive and reliable simultaneously detection of PNP and ONP were achieved with a low limit of detection. [ABSTRACT FROM AUTHOR]

Novel 3D porous Ni/Cu(OH) 2 nanospheres (Ni/Cu(OH) 2 NS) were directly grown on a Ni foam (NF) via a facile one-step potentiostatic deposition synthesis route. The resultant Ni/Cu(OH) 2 NS possessed an abundance of catalytic which gave them excellent catalytic properties for the electrochemical detection of glucose in alkaline conditions. Using these NS in a promising and integrated non-enzymatic glucose sensor, a high sensitivity of 8722 μA mM−1 cm−2, a low detection limit of 1.27 μM, and a linear detection range from 10 to 1490 μM were obtained at the Ni/Cu(OH) 2 NS/NF anode. Additionally, the proposed sensor exhibited excellent anti-interference capability, good reproducibility, and long duration stability. It was successfully applied to glucose detection in human blood serum, showing excellent effectiveness. • Porous Ni/Cu(OH) 2 nanospheres supported on the Ni foam was fabricated by a facile one-step potentiostatic deposition strategy. • As-prepared Ni/Cu(OH) 2 /NF anode shows excellent catalytic activity to glucose. • The porous Ni/Cu(OH) 2 nanospheres could offer more abundant active sites and easier access to electrolyte. [ABSTRACT FROM AUTHOR]