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Electrochemical aptasensor based on nanocomposite and RecJf exonuclease-assistant signal amplification strategy for di(2-ethylhexyl)phthalate (DEHP) detection.

The AuNFs and AuSPs were successfully synthesized for labeling antibodies. The AuSP-ICS and AuNF-ICS were successfully fabricated for sensitive ZEN detection. The AuNF-ICS exhibited satisfactory sensitivity and specificity.

In this paper, gold nanoparticles were combined with aflatoxin B1-aptamer as a single probe via the specific binding between aflatoxinB1 with aptamer, designing a colorimetric detection method. Meanwhile, an immunochromatographic strip with gold nanoparticles modified by complementary chains of aflatoxin B1 aptamer as the probe was developed for rapid detection of aflatoxin B1. Under the optimal conditions, the linear detection range of the colorimetric method was 0.5–50 ng/mL, the minimum detection limit was 0.5 ng/mL, the detection range of the immunochromatographic strip was 0.5–500 ng/mL, the minimum detection limit was 0.5 ng/ mL, and the semi-quantitative limit of detection (LOD) was 51 ng/mL. Finally, comparing the two methods, it is concluded that immunochromatographic strip detection is more sensitive, accurate and celerity. The recoveries of test samples were from 97.3–120%. All detections could be accomplished within 10 min, indicating that the strip could be a potentially effective tool for rapid on-site detections.

Developing rapid detection technology for adenosine triphosphate (ATP) is crucial in quality supervision and food safety. Herein, an electrochemical aptasensor based on an aptazyme-catalyzed signal amplification strategy is constructed for ATP detection using polyethyleneimine-functionalized molybdenum disulfide (PEI-MoS

Here, a label-free impedance-based electrochemical sensor was developed for the quantitative detection of Pb

A novel ultrasensitive electrochemical aptasensor was proposed for quantitative detection of Cd

The abuse of chloramphenicol (CAP) in animal-derived products leads to serious food safety problems, so the sensitive and accurate determination of CAP residues has great noteworthiness for public health. Herein, we present a novel electrochemical aptasensor that incorporates a poly(diallyldimethylammonium chloride) functionalized graphene/Ag@Au nanosheets (PDDA-Gr/Ag@Au NSs) composite modified electrode and a DNAzyme signal amplification effect triggered by a triple-helix molecular switch (THMS) for detecting CAP. The PDDA-Gr/Ag@Au NSs composite has the advantages of high surface area, great conductivity, and dispersibility and has successfully improved the electrochemical performance of the electrode. Specific interaction with CAP will cause the signal transduction probe (STP) to be released from the THMS. After that, the DNAzyme will be activated with the help of Pb

Aflatoxin B1 (AFB

Due to improper storage, the presence of patulin in fruits poses a threat to food safety. Herein, a one-step dual amplification strategy-based electrochemical aptasensor was proposed for patulin detection. Silver-palladium nanoparticles (AgPdNPs) with a hollow and branched structure were used as a supporting material for thionine to provide numerous attachment sites. AuNFs/g-C

An electrochemical aptasensor is fabricated for lead ion (Pb2+) detection based on catalytic hairpin assembly as signal amplification. Biomass porous carbon derived from soybean straw (PCs) is used to load platinum nanoparticles (PtNPs), which are introduced as mimetic enzymes to catalyze the hydroquinone–H2O2 system. In the presence of Pb2+, the complementary DNA (cDNA) releases from aptamer-cDNA and hybridizes with hairpin DNA1 (HP1) on the electrode surface. After bio-hairpin DNA2 (bio-HP2) is added, hybridization between HP1 and bio-HP2 further releases cDNA, which participates in the next cycle and triggers amplification, eventually forming a large number of bio-HP2/HP1 on the electrode surface. Then PtNPs@PCs immobilize on the electrode surface by specific binding of streptavidin with biotin, and catalyze the oxidation of hydroquinone in the presence of H2O2. The produced electrochemical signal depends on the concentration of Pb2+. The developed biosensor exhibits a wide linear range from 50 pM to 1000 nM with a detection limit of 18 pM, and high selectivity for Pb2+ over other environmentally relevant metal ions at concentration ratios of 100. The recoveries of Pb2+ in real samples were 93.5–108%. Thus, the proposed biosensor can provide an efficient method for sensitive and selective detection of Pb2+ in real samples.

A sensitive electrochemical sensor for the detection of Pb

Excessive residues of semicarbazide (SEM) can accumulate in animals after the original drug has been abused, posing a risk to human health. Herein, based on multifunctional silica-initiated dual mode signal response, a novel competitive-type immunosensor was constructed for ultrasensitive detection of SEM. As a preliminary signal amplification platform for immunosensors, polyethyleneimine reduced graphene oxide composite gold nanorods (PEI-rGO/AuNRs) modified gold electrodes (AuE) provide a high specific surface area and high electrical conductivity. The thionine-aminated silica nanospheres-AuPt (thi-SiO

Herein, an aptasensor based on target-induced strand displacement (TISD) strategy was developed for sensitive detection of T-2 toxin. Gold nanoparticles@ aminated manganese dioxide (AuNPs@NH

A fluorescent aptasensor was constructed to detect lead ion (Pb

As a common heavy metal ion with strong toxicity and wide distribution, lead ions (Pb

The simultaneous detection of multiple mycotoxins is of great significance for food safety and human health. Herein, a simple, convenient and accurate fluorescent aptasensor was designed based on the dual cross DNA nanostructure for the simultaneous detection of ochratoxin A (OTA) and aflatoxin B

The authors designed a sensitive label-free electrochemical aptasensor for the detection of sulfaquinoxaline (SQX), including the AuPd NPs@UiO-66-NH

A fluorescent aptasensor was constructed to detect lead ion (Pb2+). Complementary DNA with sulfhydryl group (SH-cDNA) were loaded on gold nanoflowers materials (Au NFs) through Au–S bonds. Then, based on complementary base pairing between FAM modified Pb2+ aptamer (FAM-Apt) and Au NFs/SH-cDNA system, a Au NFs/SH-cDNA/FAM-Apt aptasensor was constructed. The fluorescence of FAM was quenched by Au NFs due to the fluorescence resonance energy transfer (FRET). Upon addition of Pb2+ and RecJf exonuclease (RecJf Exo) for 1.5 h, the Apt changed to a G-quadruplex structure due to the high affinity between Pb2+ and its aptamers, which lead to a large recovery in the fluorescence intensity. Under the optimized conditions, the presented aptasensor revealed high selectivity toward Pb2+ in the concentration range of 0.5 nM–1 μM, with a limit of detection (LOD) of 0.285 nM. Besides, the designed aptasensor was successfully used to recognize Pb2+ with excellent selectivity, reproducibility and stability in tap water and tea, providing a potential platform for Pb2+ detection in actual samples.

The feasibility of developing a multispectral imaging method using important wavelengths from hyperspectral images selected by genetic algorithm (GA), successive projection algorithm (SPA) and regression coefficient (RC) methods for modeling and predicting protein content in peanut kernel was investigated for the first time. Partial least squares regression (PLSR) calibration model was established between the spectral data from the selected optimal wavelengths and the reference measured protein content ranged from 23.46% to 28.43%. The RC-PLSR model established using eight key wavelengths (1153, 1567, 1972, 2143, 2288, 2339, 2389 and 2446 nm) showed the best predictive results with the coefficient of determination of prediction (R2P) of 0.901, and root mean square error of prediction (RMSEP) of 0.108 and residual predictive deviation (RPD) of 2.32. Based on the obtained best model and image processing algorithms, the distribution maps of protein content were generated. The overall results of this study indicated that developing a rapid and online multispectral imaging system using the feature wavelengths and PLSR analysis is potential and feasible for determination of the protein content in peanut kernels.

Herein, PtPd nanoparticles compound polyethyleneimine-functionalized reduced graphene oxide (PtPd NPs/PEI-rGO) was used as the substrate material, Exonuclease III (Exo III)-assisted triple-amplified was integrated into electrochemical platform for the detection of deoxynivalenol (DON). PtPd NPs/PEI-rGO as the substrate material increased the surface area of the electrode and improved the conductivity of the electrode. The specific binding of the DON and the aptamer triggered Exo III-assisted cyclic amplification in sample solution and generated trigger (Tr) (cycle I). The hybridization of Tr and Locking probe (LP) activated DNA Walker (W-DNA) (cycle II). Then, W-DNA run continuously with the assistance of Exo III, eventually the current signal was decreased (cycle III). However, in the absence of DON, DNA machine was not driven and the electric signal was relatively high. Under optimal conditions, the detection limit of the aptasensor is 6.9 × 10−9 mg mL−1, and the detection range from 1 × 10−8 mg mL−1 to 1 × 10−4 mg mL−1. In addition, the stability, reproducibility, and real sample detection ability of the aptasensor were studied and obtained satisfactory results.

The authors designed a sensitive label-free electrochemical aptasensor for the detection of sulfaquinoxaline (SQX), including the AuPd NPs@UiO-66-NH2/CoSe2 nanocomposites and RecJf exonuclease-assisted target recycle signal amplification strategy. AuPd NPs@UiO-66-NH2/CoSe2 nanocomposite with excellent conductivity and numerous active sites was successfully synthesized to provide a favorable sensing platform and load more double-strand DNA (dsDNA) on the electrode surface. The negatively charged phosphate group of the oligonucleotide and [Fe (CN)6] 3-/4- repel each other electrostatically, resulting in very low electrical signals. In the presence of SQX, its corresponding aptamer will be released from the double-stranded structure and then digested by RecJf exonuclease, which resulted in the SQX being released to initiate the next recycling to help amplify the DPV signal. Under the optimal conditions, the peak current has a linear relationship with the logarithmic of SQX concentration in the range of 1 pg/mL∼100 ng/mL and the obtained detection limit was 0.547 pg/mL. Furthermore, the contrasted aptasensor possess reliable specificity, reproducibility and stability toward SQX, and has been applied to detect SQX in pork samples with a satisfied recovery varied from 94.40% to 95.98%.

The potential of hyperspectral imaging in the spectral range of 1000–2500 nm with multivariate analysis for the prediction of oil and protein concentrations in five peanut cultivars was investigated. Quantitative partial least squares regression (PLSR) models were established using the extracted spectral data from hyperspectral images and the reference measured oil and protein concentrations. The PLSR models established using the whole spectral data pretreated by the multiplicative scatter correction (MSC) method showed good results for predicting the oil concentration with a determination coefficient (RP2) of 0.945 and root mean square errors of prediction (RMSEP) of 0.196 and for predicting the protein concentration with RP2 of 0.901 and RMSEP of 0.441. In addition, eight optimal wavelengths were selected for protein and oil contents, respectively, using the regression coefficients of the PLSR analysis and used for simplifying the obtained models. The simplified PLSR models also showed good performances with Rp2 of 0.933 and 0.912 for predicting oil and protein concentrations. The whole results demonstrated that the NIR hyperspectral imaging technique coupled with chemometric analysis is a promising tool for rapid and non-destructive determination of oil and protein concentrations in peanut kernels and has the potential to develop a multispectral imaging system for future on-line detection of peanut quality.

In this work, using DNA and exonuclease-I (Exo-I) as signal amplification strategy, a novel and facile electrochemical aptasensor was constructed for fumonisin B1 (FB1) detection. The G-rich complementary DNA (cDNA) was immobilized onto the electrode surface. Then, aptamer of FB1 was hybridized with cDNA to form double-stranded DNA. In the absence of FB1, double-stranded DNA and G-rich cDNA on the electrode surface promoted effectively methylene blue (MB) enrichment and amplified the initial electrochemical response. In the presence of FB1, the combination of aptamer and FB1 led to the release of aptamer from the electrode surface and the expose of 3′ end of single-stranded cDNA. When Exo-I was added onto the electrode surface, the single-stranded cDNA was degraded in the 3′–5′ direction. The decrease of double-stranded DNA and G-rich cDNA resulted in the less access of MB to the electrode surface, which decreased the electrochemical signal. The experimental conditions including incubation time of FB1, the amount of Exo-I and incubation time of Exo-I were optimized. Under the optimal conditions, the linear relationship between the change of peak current and the logarithmic concentration of FB1 was observed in the range of 1.0 × 10−3–1000 ng mL−1 with a low limit of detection of 0.15 pg mL−1. The experimental results showed that the prepared aptasensor had acceptable specificity, reproducibility, repeatability and stability. Therefore, this proposed aptasensor has a potential application in the food safety detection.

The presented voltammetric mercury(II) sensor is based on the specific interaction between Hg(II) ion and thymine-thymine base pairs. Reduced graphene oxide is functionalized with gold nanorods and then loaded with thionine and streptavidin (RGO@AuNR-TH-SA). A T-rich thiolated DNA (S1) is firstly immobilized on a gold electrode. In the presence of Hg (II), the T-rich biotin-DNA (biotin-S2) binds to S1 via T-Hg(II)-T interaction. Then, the RGO@AuNR-TH-SA is linked to the gold electrode by specific binding between SA and biotin-S2. This produces an electrochemical signal (at -0.208 V vs. Ag/AgCl) of TH that depends on the concentration of Hg (II). The peak current increases linearly in the 1 to 200 nM Hg (II) concentration range, and the detection limit is 0.24 nM. The sensor is highly selective for Hg (II) over other environmentally relevant metal ions, even at concentration ratios of1000. Graphical abstract Schematic representation of a voltammetric biosensor for mercury(II) using reduced graphene oxide@gold nanorods (RGO@AuNRs) and thymine-Hg(II)-thymine interaction. It is based on the fact that RGO@AuNR can strongly adsorb thionine (TH) and streptavidin to realize the signal amplification.

In this work, a sensitive dual mode competitive electrochemical immunosensor based on differential pulse voltammetry (DPV) and square wave voltammetry (SWV) response modes for quantitative determination of dibutyl phthalate (DBP) was successfully established. According to diethylenetriamine (DETA) assisted hydrothermal strategy, a novel N-doped graphene/CoSe2 nanobelt composite was prepared. Afterwards, PEI functionalized NG-CoSe2 and gold nanowires (AuNWs) were further compounded as a preliminary signal amplification platform for immunosensor. Thionine (Thi)-loaded Au@Pt and secondary antibody (Ab2) connected as a signal label. The immobilized coating antigen DBP-BSA and the DBP compete for limited antibody binding sites. The concentration of DBP can be determined by DPV detect the Thi signal loaded on the Thi-Au@Pt-Ab2 label. It can also be determined by SWV mode to detect the current generated by the reaction system of H2O2 and o-phenylenediamine (o-PD) catalyzed by Thi-Au@Pt with peroxidase like properties. Under optimum conditions, the linear ranges of the DPV and SWV modes were 1 pg mL−1∼1 μg mL−1. And LOD were 0.486 pg mL-1 (DPV) and 0.711 pg mL-1 (SWV), respectively. Besides, it exhibited outstanding selectivity, reproducibility, stability and can be used for sensitive detection of DBP in real samples.

A sensitive electrochemical biosensor was constructed for Hg2+ detection based on peonylike Cu-MOFs in situ growth of PtPd NPs bimetallic label S1 and Mg2+-dependent DNAzyme-driven DNA Walker dual amplification signal strategy. The hairpin DNA (HP) and signal label Cu-MOFs@PtPd NPs/S1 were first used to self-assemble on the gold nanorods/poly (diallyldimethylammonium chloride) functionalized graphene (AuNRs/PDDA-Gr) modified electrode, at this time, Cu ions can undergo a valence change to produce a larger initial signal. Here, we designed S2 that can perform dual functions and contains two sequences, on was a substrate sequence of the Mg2+-dependent DNAzyme and the other was a sequence complementary to HP. In the presence of target Hg2+, HP was opened and hybridized with enzymatically sequenced DNA Walker (S2) to preferentially form thymine-Hg2+-thymine (T-Hg2+-T). Then, DNA Walker exhibited catalytic activity of DNAzyme in the presence of Mg2+ to continuously cleave Cu-MOFs@PtPd NPs/S1, resulting in a decrease of electrochemical signal. Under optimal conditions, the change of current was linearly related to the negative logarithm of the Hg2+ concentration in the detection range of 0.001–100 nM with a low detection limit of 0.52 pM. Moreover, the proposed aptasensor was successfully applied in detection of milk powder samples.

A sensitive and selective electrochemical Pb2+ sensor was developed based on GR-5 DNAzyme and exonuclease III-assisted target recycling amplification. When target Pb2+ existed, GR-5 DNAzyme was cleaved into two free DNA fragments. One of the fragments could open the hairpin DNA (HP1) modified on the electrode to form DNA duplex with blunt end at the 3′-terminus and triggered Exo III cleavage process. A large amount of residual part of HP1 were obtained by the Exo III-aided recycling which could hybridized with another hairpin DNA labeled with methylene blue, resulting in the dramatic increase of current. The electrochemical signal of methylene blue positive correlated with the Pb2+ concentration. The proposed sensor has the concentration ranging from 10−11 to 8×10−6 mol/L with a detection limit of 2.74 p mol/L. Moreover, the analysis of Pb2+ concentration in real water revealed that the proposed biosensor has a promising application in environment monitoring.