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An ultrasensitive and selective method for Bisphenol A (BPA) detection using aptamer-BPA and real-time quantitative polymerase chain reaction (RT-qPCR) technology is reported, in which biotin-modified aptamer DNA (BPA) is fixed on the inner wall of a streptavidin-coated PCR tube via biotin-avidin interactions and the template is fixed through the complementary base pairing with aptamer DNA. Upon the addition of BPA, the template DNA could be off from the inner wall of PCR tube, which results from aptamer DNA interacted specifically with BPA. Thus, the number of template DNA change result from the BPA concentration is readily seen by cycle threshold (Ct) values. The sensor exhibited an excellent linear response between Ct values and BPA concentration in the range of 1-500 nM and the detection limit of this method for aqueous BPA was as low as 0.7 nM. In addition, this method showed good selectivity for BPA over its analogues. [ABSTRACT FROM AUTHOR]

The detection of ultralow concentrations of mercury is a currently significant challenge. Here, a novel strategy is proposed: the colorimetric detection of Hg 2+ based on the aggregation of gold nanoparticles (AuNPs) driven by a cationic polymer. In this three-component system, DNA combines electrostatically with phthalic diglycol diacrylate (PDDA) in a solution of AuNPs. In the presence of Hg 2+ , thymine (T)-Hg 2+ -T induced hairpin turns are formed in the DNA strands, which then do not interact with PDDA, enabling the freed PDDA to subsequently facilitate aggregation of the AuNPs. Thus, according to the change in color from wine-red to blue-purple upon AuNPs aggregation, a colorimetric sensor is established to detect Hg 2+ . Under optimal conditions, the color change is clearly seen with the naked eye. A linear range of 0.25–500 nM was obtained by absorption spectroscopy with a detection limit of approximately 0.15 nM. Additionally, the proposed method shows high selectivity toward Hg 2+ in the presence of other heavy metal ions. Real sample analysis was evaluated with the use of lake water and the results suggest good potential for practical application. [ABSTRACT FROM AUTHOR]

An effective and facile approach for mercury detection is essential for environmental protection and human health. In this study, we propose a novel strategy to develop a highly sensitive and selective method for the detection of mercury ions using real-time quantitative polymerase chain reaction (RT-qPCR) technology and the specific binding of Hg2+in thymine–thymine mismatch complexes. The signal for detection of Hg2+was generated using RT-qPCR amplification of a template strand of DNA. The sensor exhibited an excellent linear response between the cycle threshold (Ct) and mercury ion concentration in the range of 0.05–100 nM. Under optimised conditions, the detection limit of this method for aqueous Hg2+was as low as 30 pM. In addition, this system showed good selectivity for Hg2+over other metal ions. This new approach shows significant potential for detection of Hg2+in water and other samples. [ABSTRACT FROM PUBLISHER]

The method referred to as 'systemic evolution of ligands by exponential enrichment' (SELEX) was introduced in 1990 and ever since has become an important tool for the identification and screening of aptamers. Such nucleic acids can recognize and bind to their corresponding targets (analytes) with high selectivity and affinity, and aptamers therefore have become attractive alternatives to traditional antibodies not the least because they are much more stable. Meanwhile, they have found numerous applications in different fields including food quality and safety monitoring. This review first gives an introduction into the selection process and to the evolution of SELEX, then covers applications of aptamers in the surveillance of food safety (with subsections on absorptiometric, electrochemical, fluorescent and other methods), and then gives conclusions and perspectives. The SELEX method excels by its features of in vitro, high throughput and ease of operation. This review contains 86 references. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report on the application of versatile gold nanorods (GNRs) in optical sensors for the detection of antibiotics. The target analyte, Gentamicin (GM) and ovalbumin (OVA) – antigen-modified GNRs together competed with antibody-modified GNRs, then influenced the formation of side-by-side aggregates of the GNRs by antibody–antigen interactions. Accordingly, the UV–vis absorption intensity of the side-by-side aggregates was changed in the presence of the target analyte. This assay allowed the selective determination of GM in the range of 0.1–20ng/mL, and the limit of detection (LOD) of GM was 0.05ng/mL. Furthermore, compared with the traditional plate-based immunoassay, the developed method was easy to perform without washing cycles and the results could be read as soon as the nanoprobe-analyte incubation was complete. Therefore, the developed method could be a promising tool for the detection of antibiotic residues. [Copyright &y& Elsevier]

Abstract: In this paper, we demonstrate the application of versatile G-quadruplex–hemin DNAzymes in an immunoassay for detecting Microcystin-LR (MC-LR). Taking advantage of the high peroxidase activity of G-quadruplex–hemin complexes and the enhancement effect of gold nanoparticles (AuNPs), the method showed simple, high sensitive and selectivity detection of target toxin residues in water samples. The coated antigen, MC-LR–ovalbumin (OVA) coated on a plate, competed for MC-LR antibody with added target analyte to form antibody–antigen immune complexes. Subsequently, the immune complex reacted with G-quadruplex-labeled secondary antibodies for colorimetric detection of MC-LR. This assay specifically determined MC-LR in the linear range of 0.1–10ng/ml, with a limit of detection (LOD) of 0.05ng/mL for MC-LR. The results indicated that the novel immunoassay was an alternative to traditional plate-based immunoassay for MC-LR residue screening due to this method met the standard of World Health Organization (WHO) requirements for MC-LR content in drinking water (1ng/mL). [Copyright &y& Elsevier]

In this study, Ag and Cu 2 O nanoparticles modified flower-like ZnO nanostructures have been successfully synthesized by stepwise method, and the photocatalytic properties were investigated in detail. High-resolution transmission electron microscopy, X-ray diffractions analysis, X-ray photoelectron spectroscopy and scanning electron microscopy were used to analyze the samples. Meanwhile, the derived nanoparticles' structured and morphologic characters were analyzed by Brunauer–Emmett–Teller. The results have shown that the 3D flower-like ZnO microspheres were composed of 2D ZnO nanosheets decorated Ag and Cu 2 O and exhibiting flower-like Ag@Cu 2 O/ZnO architectures. We studied the optical absorption (UV–vis) as well as emission (PL) characters of the specimen and the outcomes suggested more superior photocatalytic characteristics for cuprous oxide and silver co-doped zinc oxide sample compared to other samples. Electron Paramagnetic Resonance test results show that there are mainly ⋅ O 2 − , h + and O H • free radicals in the process of CR degradation. A Radical-trapping test indicated that of ⋅ O 2 − and h + was more effective than O H • in the degradation of CR. [ABSTRACT FROM AUTHOR]

Chlordimeform (CDM) is a broad-spectrum and highly effective insecticide and acaricide used to control pests in agriculture. We produced two monoclonal antibodies (mAbs) against CDM and developed an immunochromatographic assay to screen CDM in cucumbers and tomatoes. MAb 4A3 had high sensitivity with a 50% inhibitory concentration of 0.287 ng mL−1. The assay had a cut-off value of 25 μg kg−1 and a visual limit of detection (vLOD) of 1 μg kg−1 in cucumbers and a cut off value of 50 μg kg−1 and a vLOD of 2.5 μg kg−1 in tomatoes. The calculated limit of detection (cLOD) in cucumbers and tomatoes was 0.115 μg kg−1 and 0.215 μg kg−1, respectively. The recovery rates were 97.9% to 106.9% for cucumbers and 97.8% to 107.4% for tomatoes, consistent with the results obtained from indirect competitive ELISA. Our findings showed that the immunochromatographic assay is an efficient and accurate method for CDM detection in cucumbers and tomatoes. [ABSTRACT FROM AUTHOR]

In this study, a highly specific and sensitive monoclonal antibody against dicofol (DIC) was prepared and used to create a colloidal gold immunochromatographic strip (ICS) for the quantitative analysis of DIC in liquorice and Angelica sinensis samples. We found that for both the liquorice and Angelica sinensis samples, the cut-off value for the ICS was 500 ng g−1, respectively, and using a colloidal gold test strip reader, the half-maximal inhibitory concentrations (IC50) were found to be 35 ng g−1 and 88 ng g−1, the limits of detection were 2 ng g−1 and 3 ng g−1, and the linear detection scopes (IC20–IC80) were from 6 to 201 ng g−1 and from 10 to 819 ng g−1, respectively. In the recovery test, we found that recoveries were within the range of 90.6% to 97.2% and the coefficients of variation were less than 8.6% in the intra-assay and inter-assay for the liquorice samples and the recoveries ranged from 90.8% to 97.3% and the coefficients of variation were less than 9.1% in the intra-assay and inter-assay for the Angelica sinensis samples. The established ICS assay could be used for the rapid quantitative screening of chemicals in Chinese traditional medicinal materials. [ABSTRACT FROM AUTHOR]

Mechanisms of glutathione (GSH) over-accumulation in mutant Saccharomyces cerevisiae Y518 screened by ultraviolet and nitrosoguanidine-induced random mutagenesis were studied. Y518 accumulated higher levels of GSH and l-cysteine than its wild-type strain. RNA-Seq and pathway enrichment analysis indicated a difference in the expression of key genes involved in cysteine production, the GSH biosynthesis pathway, and antioxidation processes. GSH1, MET17, CYS4, GPX2, CTT1, TRX2, and SOD1 and the transcriptional activators SKN7 and YAP1 were up-regulated in the mutant. Moreover, Y518 showed a dysfunctional respiratory chain resulting from dramatically weakened activity of complex III and significant elevation of intracellular reactive oxygen species (ROS) levels. The supplementation of antimycin A in the culture of the parent strain showed equivalent changes of ROS and GSH level. This study indicates that defective complex III prompts abundant endogenic ROS generation, which triggers an oxidative stress response and upregulation of gene expression associated with GSH biosynthesis. This finding may be helpful for developing new strategies for GSH fermentation process optimization or metabolic engineering. [ABSTRACT FROM AUTHOR]

Microemulsion cleaning method has been proved to be an effective way to clean oily sludge with low interfacial tension and high solubilizing ability for non-miscible liquids. In this paper, the percentage range of the microemulsion in the formulation was obtained by studying phase behavior of the microemulsion. The response surface method was used to model and optimize the microemulsion to obtain the best formulation: n-BuOH content at 9.89%, NaCl content at 2.24% and AES/APG ratio at 3.75, and the oil removal rate reached 97.28%. Meanwhile, the cleaning conditions of oil sludge were also optimized by the response surface method and the optimal cleaning parameters were determined as liquid-solid ratio at 4.2, stirring rate at 157 r·min−1, and stirring time at 38 min. In addition, some experiments were carried out to confirm the simulation results, affording the oil removal rate of 98.79%. SEM and FTIR confirmed that the oil on the sludge can be removed by microemulsion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rapid ochratoxin A (OTA) detection with the commercial portable glucose meter. • Glucose as the intermediate bridge molecule for OTA detection. • Aptamer based recognition system integrated with the invertase catalysis system. • OTA sensing event transferred to catalytic glucose production system. • OTA detection results can be directly judged from portable glucose meter. On-site screening of biotoxins is of great importance for food safety. A new electrochemical-biosensing strategy was constructed for ochratoxin A (OTA) detection by direct using ready-made commercial portable-glucose-meter (PGM). Aptamer against OTA was adopted as the recognition probe and pre-immobilized onto the sensing interface. The complementary biotin-modified probe was further decorated by hybridization. Biotinylated invertase was further introduced onto the sensing system with streptavidin, which also acted as the signal amplification unit. The invertase, which was depended on the amount of OTA, produced the glucose from sucrose in the sensing solution. The glucose could be directly and conveniently measured with PGM. Quantitative analysis of OTA was achieved with a linear range from 0.5 ng/mL to 10 ng/mL and detection limit of 0.45 ng/mL. Of significance, it has been successfully applied for OTA analysis in rice with satisfied recoveries. This unique PGM-based electrochemical platform reveals prospective potential in food safety monitoring. [ABSTRACT FROM AUTHOR]

• An immunosensor was developed for the determination of amanitins. • Half-maximal inhibitory concentration was 0.48 ng/mL and the LOD was 0.095 ng/mL. • Good correlations of the results verified by immunosensor and LC–MS/MS. Amanitin (AMA) is responsible for human fatalities after ingestion of poisonous mushrooms, thus, a rapid and accurate detection method is urgently needed. Here, gold nanoparticle-based immunosensor with monoclonal antibody against AMA was constructed for rapid detection of alpha- and beta-amanitin (α- and β-AMA) in mushroom, serum and urine samples. Under optimized conditions, the visual limits of detection (vLOD) and calculated LOD for α-AMA and β-AMA in mushroom were 10 ng/g, 20 ng/g, and 0.1 ng/g, 0.2 ng/g, respectively. Analysis of wild mushroom samples was also performed using a strip scan reader in the 10 min range. Furthermore, in mushrooms containing amatoxins results were confirmed and compared with those determined by liquid chromatography tandem mass spectrometry. Thus, this immunosensor provided a useful monitoring tool for rapid detection and screening of mushroom samples and in serum and urine from subjects who accidentally consumed AMA-containing mushrooms. [ABSTRACT FROM AUTHOR]

Meat and meat products are one of the valuable foods that provide a variety of essential nutrients for human beings, and their authentication is of great significance for guaranteeing food quality and safety and also the human health. In this research, we present a proof-of-concept strategy of loop-mediated isothermal amplification (LAMP) coupled fluorescence-anisotropy (FP) for rapid, sensitive and accurate judgement of adulteration. Relationship between LAMP and FP is easily constructed by using FITC-labeled primer, which shows limited FP signal at its free state because of fast rotation. With pork DNA, the short primer can be efficiently amplified into macromolecules by LAMP, undergoing significant increase of molecular weight restricting the rotation of FITC. This change leads to a dramatic enhancement of FP signal for adulteration screening. Results show that LAMP-FP well integrates the high efficiency of LAMP with the simplicity of FP, achieving detection limit of 0.01% (wt. %). The performance of LAMP-FP strategy is comparable to those of qPCR. Importantly, this unique method is also available for the commercial processed products. We expect this LAMP-FP will provide a new direction to build versatile analytical tools in food safety monitoring. • A proof-of-concept strategy of LAMP coupled portable FP (LAMP-FP) is constructed for authentication of pork adulteration. • LAMP-FP can achieve rapid and accurate authentication of pork adulteration. • This strategy well integrates the extraordinary amplification efficiency of LAMP with the simplicity of FP. • Satisfied results are achieved for authentication of pork adulteration. • Practical samples are well determined with this new proposed strategy. [ABSTRACT FROM AUTHOR]

Gold-based immunochromatographic strip for rapid ketoconazole detection with a visual limit of detection of 0.5 ng/g and a cut-off value of 20 ng/g. [Display omitted] • A novel hapten of ketoconazole was synthesized. • A highly sensitive and specific monoclonal antibody against ketoconazole was developed. • A half-maximal inhibitory concentration is 0.7 ng/mL. • A colloidal gold immunochromatographic strip was developed for monitoring ketoconazole residues in chicken sample. • Good correlations of the results obtained by CGIA and LC-MS/MS. We developed a highly sensitive and specific monoclonal antibody (mAb) for ketoconazole (KCZ) detection in chicken samples. From indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) analysis, the 50% inhibitory concentration of the mAb was 0.7 ng/mL, and the cross-reactivity with fluconazole, imidazole, itraconazole, and voriconazole was <1%. Using indirect competitive enzyme-linked immunosorbent assay, spiked sample recovery was 92.5%–102.7%. Under optimal conditions, we also developed a colloidal gold immunochromatographic assay (CGIA) to detect KCZ residues in chicken samples, with a visual limit of detection of 0.5 ng/g and a cut-off value of 20 ng/g. When data were assessed using liquid chromatography with tandem mass spectrometry, no significant differences were found between assays. Also, strip results were revealed in 10 min. Therefore, our CGIA has great potential for rapidly detecting KCZ residues in chicken samples. [ABSTRACT FROM AUTHOR]

It is essential that the novel biomarkers discovered by means of advanced detection tools based on metabonomics could be used for long-term monitoring in food safety. By summarizing the common biomarkers discovery flowsheet based on metabonomics, this review evaluates the possible application of metabonomics in new biomarker discovery, especially in relation to food safety issues. Metabonomics have the advantages of decreasing detection limits and constant monitoring. Although metabonomics is still in the developmental stage, we believe that, based on its properties, such as noninvasiveness, sensitivity, and persistence, together with rigorous experimental designs, new and novel technologies, as well as increasingly accurate chemometrics and a relational database, metabonomics can demonstrate extensive application in food safety in the postgenome period. [ABSTRACT FROM PUBLISHER]

A rapid, sensitive, specific and simple method based on Fluorescence Polarization Immunoassay (FPIA) was developed for the quantitative detection of Bisphenol A in water. 4, 4-Bis (4-hydroxyphenyl) valeric acid (BHPVA) was selected as the hapten to produce the immunogen. Fluorescein-labeled Bisphenol A derivatives (tracers) with different structures were synthesized and purified by thin layer chromatography. Based on the polyclonal antibody and tracers, an optimized FPIA method was developed with a detection limit (10%% inhibition) of 2 μg L−1 and a linear working range of 20 to 800 μg L−1. FPIA was suitable for screening a large number of samples. The recoveries of fortified Tai lake water samples ranged from 91.85 to 102.78%%, and tap water samples ranged from 90.36 to 96.01%%. The coefficients of variation were all less than 20%%. This FPIA method, which did not require a complicated cleanup process, proved to be very useful for the screening of Bisphenol A in environmental water samples. [ABSTRACT FROM AUTHOR]

Abstract: An aptamer-based chromatographic strip assay method for rapid toxin detection was developed. The aptamer-based strip assay was based on the competition for the aptamer between ochratoxin A and DNA probes. The sensing results indicated that the sensitivity of the aptamer-based strip was better than that of conventional antibody-based strips. The visual limit of detection of the strip for qualitative detection was 1ng/mL while the LOD for semi-quantitative detection could down to 0.18ng/mL by using scanning reader. The recoveries of test samples were from 96% to 110%. All detections could be achieved in less than 10min, indicating that the aptamer-based strip could be a potential useful tool for rapid on-site detections. [ABSTRACT FROM AUTHOR]

Abstract: Melamine toxicity causing the renal failure and death of animals and humans has recently attracted worldwide attention. Developing an easy, fast, and sensitive method for the routine melamine detection is of great importance. Herein, we report the colorimetric sensing of melamine, based on the 18-crown-6 ether functionalized gold nanoparticles (GNPs) through the formation of cavity complexes with amines. Based on high extinction coefficients and spectral sensitivity of the surface plasmon resonance band of the GNPs, the rapid and sensitive melamine detection was achieved both visually and spectroscopically. Under the optimal conditions, melamine could be selectively detected in a concentration range from 10 to 500ppb with a limit of detection as 6ppb (3σ), which is much lower than the strictest melamine safety requirement of 1ppm. To demonstrate the selectivity and practicality of the method, melamine detection was realized in the real complex samples (dairy) with excellent analyte concentration recovery, indicating its applicability for real-time monitoring of toxins in common products. Crown ether assembly of GNP also opens a new route for the formation of three-dimensional pseudorotaxane-like assemblies of nanoparticles that can be applicable to a variety of amine-bearing ligands. [ABSTRACT FROM AUTHOR]

Abstract: Environmental monitoring requires rapid and reliable analytical tools that can perform sample analysis with minimal sample handling. Nanoparticle (NP)-based environmental sensors have the potential to detect toxins, heavy metals, and organic pollutants in air, water, and soil, and are expected to play an increasingly important role in environmental monitoring. They can both improve detection and sensing of pollutants, and be used to develop new remediation technologies. Compared to traditional detection methods, NP sensors may have higher selectivity, sensitivity and stability and lower cost. This review reports on the development of sensing principles based on NP, including synthesis of specific NP components, optical sensors, electrochemical biosensors and magnetic-relaxation sensors. Advantages over other environmental monitoring methods are discussed. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasensitive and rapid electrochemical platform for the specific detection of ochratoxin A (OTA) was developed. In this method, three single-stranded DNA molecules, including the aptamer, were immobilized on the surface of an electrode. Binding of the OTA target analyte to the aptamer changed the redox current of methylene blue (MB), which was used as the electrochemical probe, in a manner that was dependent on OTA concentration. With signal enhancement from gold nanoparticle-functionalized DNA, the sensitivity of this method for OTA was as low as 30pg/mL, and the effective sensing range was from 0.1 to 20ng/mL. To investigate the sensing process, the conformational switch of the aptamer was studied by circular dichroism (CD), which confirmed the recognition of the aptamer by the target OTA. Given its sensitivity and rapid detection, we believe this approach has the potential to be a main technology for the detection of toxins in the field of food safety, and in other areas. [ABSTRACT FROM AUTHOR]

Here, we report a simple fluorescent strip sensor based on aptamer–quantum dots technology that can meet toxin monitoring demands using ochratoxin A (OTA) as a model toxin. The limit of the detection (LOD) for the fluorescent strip was 1.9 ng mL−1, while the time needed for the detection is only 10 min; this conforms to the standards of World Health Organization (WHO) or better. Overall functional parameters are also better than the analogous characteristics of gold nanoparticle strips.High selectivity was maintained as well, making them suitable for the samples with complex solution composition. [ABSTRACT FROM AUTHOR]

Three-dimensional nanoporous copper (NP-Cu) for the first time has been used as an enhanced material for ultrasensitive detection of carbendazim by electrochemistry method. The NP-Cu was fabricated by dealloying Al Cu alloy ribbons, which was characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The NP-Cu shows bicontinuous nanoporous structure with ligaments of ~20 nm. Based on the large specific surface area and high electrocatalytic activity, the NP-Cu was used to develop an amperometric sensor for carbendazim detection. Sensing parameters such as accumulation time, suspension volume, pH, scan rate, and concentration of carbendazim were discussed. The sensor can be applied to quantification of carbendazim in the concentration range of 0.5–30 μM (R2 = 0.998), with a detection limit of 0.09 μM (S/N = 3). Moreover, the sensor showed good stability, high selectivity, and satisfactory anti-interference ability. The proposed approach was approvingly applied to electrochemical determination of carbendazim in practical sample. • Electrochemical carbendazim sensor using three-dimensional nanoporous Cu/graphene composite • The sensor exhibits low detection limit, wide linear range, high sensitivity and stability. • The sensor was successfully applied to the analysis of carbendazim in pond water. [ABSTRACT FROM AUTHOR]