Development and perspectives of rapid detection technology in food and environment.

Food safety become a hot issue currently with globalization of food trade and food supply chains. Chemical pollution, microbial contamination and adulteration in food have attracted more attention worldwide. Contamination with antibiotics, estrogens and heavy metals in water environment and soil environment have also turn into an enormous threat to food safety. Traditional small-scale, long-term detection technologies have been unable to meet the current needs. In the monitoring process, rapid, convenient, accurate analysis and detection technologies have become the future development trend. We critically synthesizing the current knowledge of various rapid detection technology, and briefly touched upon the problem which still exist in research process. The review showed that the application of novel materials promotes the development of rapid detection technology, high-throughput and portability would be popular study directions in the future. Of course, the ultimate aim of the research is how to industrialization these technologies and apply to the market.

A gold nanoparticle-based lateral flow immunoassay for atrazine point-of-care detection using a handhold scanning device as reader.

A method is described to achieve accurate quantitative detection of atrazine (ATZ) in maize by using lateral flow strips based on gold nanoparticles (GNPs) and a handheld scanning reader. GNPs of 15 nm in diameter were applied as label, and a lateral flow immune assay strip was prepared. The linear range was 5.01-95.86 ng mL-1 with a detection limit of 4.92 ng mL-1 in phosphate buffer, 4 times better than the readout by the naked eye. ATZ-spiked corn samples were also analysed. The accuracy of results of spiked samples was confirmed by ELISA and liquid chromatography-tandem mass spectrometry (HPLC), which proved the reliability of the proposed method. A handhold device with an optical scanning system was designed for on-site quantitative detection. Combined with the pretreatment, the assay could be completed in less than 20 min.

A Multichannel Flexible Optoelectronic Fiber Device for Distributed Implantable Neurological Stimulation and Monitoring.

Optical fibers made of polymeric materials possess high flexibility that can potentially integrate with flexible electronic devices to realize complex functions in biology and neurology. Here, a multichannel flexible device based on four individually addressable optical fibers transfer-printed with flexible electronic components and controlled by a wireless circuit is developed. The resulting device offers excellent mechanics that is compatible with soft and curvilinear tissues, and excellent diversity through switching different light sources. The combined configuration of optical fibers and flexible electronics allows optical stimulation in selective wavelengths guided by the optical fibers, while conducting distributed, high-throughput biopotential sensing using the flexible microelectrode arrays. The device has been demonstrated in vivo with rats through optical stimulation and simultaneously monitoring of spontaneous/evoked spike signals and local field potentials using 32 microelectrodes in four brain regions. Biocompatibility of the device has been characterized by behavior and immunohistochemistry studies, demonstrating potential applications of the device in long-term animal studies. The techniques to integrate flexible electronics with optical fibers may inspire the development of more flexible optoelectronic devices for sophisticated applications in biomedicine and biology.

Selection of an artificial paraquat-specific binding protein from a ribosome display library based on a lipocalin scaffold.

In this study, an anticalin that could specifically bind paraquat (PQ), a quaternary nitrogen herbicide, as a new set of engineered receptor protein with antibody-like properties was generated to detect PQ concentration. To this end, a native and random library was constructed and engineered to allow in vitro transcription and translation using an Escherichia coli lysate system. Meanwhile, a PQ derivative that carries an active aliphatic carboxylate group at the end of an aliphatic spacer arm was synthesized. Then, this compound was coupled covalently to the carrier protein bovine serum albumin/ovalbumin and amino-functionalized paramagnetic beads. Alternating selection in solution and immobilization in microtiter wells were used to pan mRNA-ribosome-antibody complexes. After several rounds of ribosome display, three variants were selected from a random library of the bilin-binding protein. The variants that could bind complex PQ with high affinity and exhibit IC50 values as low as 14.039 ± 0.970 ng/mL were identified. Moreover, the limits of detection reached 0.083 ± 0.011 ng/mL. Our data suggest that the generation of anticalins may provide a promising alternative to recombinant antibody fragments to create a stable receptor protein against hapten with bioanalytical relevance.

Detection of 4 quinolone antibiotics by chemiluminescence based on a novel Nor-Biotin bifunctional ligand and SA-ALP technology.

A simple and effective direct competitive chemiluminescence immunoassay for the detection of 4 kinds of quinolone antibiotics in milk was established using Nor-Biotin (biotin-modified norfloxacin [NOR]) bifunctional ligand and alkaline phosphatase-conjugated streptavidin signal amplification technology. The polyclonal antibody was obtained after the immunization of New Zealand White rabbits using norfloxacin-derived antigen. "Click chemistry" was used for the rapid and facile synthesis of the Nor-Biotin bifunctional ligand. After the optimization of the incubation time and reaction buffer, the direct competitive chemiluminescence assay method was developed and used for sensitive detection of 4 kinds of quinolone drugs (NOR, pefloxacin, ciprofloxacin, and danofloxacin). The IC50 of the 4 kinds of quinolone drugs ranged from 7.35 to 24.27 ng/mL, and the lowest detection limits ranged from 0.05 to 0.16 ng/mL, which were below their maximum residue levels, approved by the EU for treatment of food-producing animals. To demonstrate the applicability of the assay, artificially contaminated milk samples with the 4 quinolone drugs were analyzed. The mean recovery rates of the drugs ranged from 86.31% to 112.11%.

The orphan nuclear receptor Nur77 plays a vital role in BPA-induced PC12 cell apoptosis.

Bisphenol A (BPA) is a typical environmental endocrine disruptor that can migrate into organisms through skin contact, breathing, diet and various other approaches. The reproductive toxicity and neurotoxicity of BPA has been confirmed by several toxicological studies. However, the neurotoxicity of BPA is still controversial. In the present study, we used PC12 cells as a model to investigate the mechanism of BPA-induced neuronal apoptosis. BPA exposure reduced cell viability, altered cell morphology and aggravated intracellular Lactate dehydrogenase (LDH) release, intracellular Ca2+ concentration, Reactive oxygen species (ROS) levels, apoptosis and the reduction in the mitochondrial transmembrane potential (ΔΨm). Moreover, the results of the Western blot (WB) and Real-time quantitative polymerase chain reaction (RT-qPCR) assays indicated that the expression levels of Nur77 in the BPA group were down-regulated and accompanied by the downregulation of the NF-κb/Bcl-2 proteins and the upregulation of cleaved-caspase 3, which is a marker of apoptosis. However, these changes were significantly reversed with the upregulation of the Nur77 protein by introducing plasmids carrying the nur77 gene. These results indicated that BPA-induced apoptosis was closely related to Nur77-mediated inhibition of the NF-κb/Bcl-2 pathway.

State-of-the-art progress of switch fluorescence biosensors based on metal-organic frameworks and nucleic acids.

Metal-organic frameworks (MOFs) have captured substantial attention of an increasing number of scientists working in sensing analysis fields, due to their large surface area, high porosity, and tunable structure. Recently, MOFs as attractive fluorescence quenchers have been extensively investigated. Given their high quenching efficiency toward the fluorescence intensity of dyes-labeled specific biological recognition molecules, such as nucleic acids, MOFs have been widely developed to switch fluorescence biosensors with low background fluorescence signal. These strategies not only lead to specificity, simplicity, and low cost of biosensors, but also possess advantages such as ultrasensitive, rapid, and multiple detection of switch fluorescence methods. At present, researches of the analysis of switch fluorescence biosensors based on MOFs and nucleic acids mainly focus on sensing of different types of in vitro and intracellular analytes, indicating their increasing potential. In this review, we briefly introduce the principle of switch fluorescence biosensor and the mechanism of fluorescence quenching of MOFs, and mainly discuss and summarize the state-of-the-art advances of MOFs and nucleic acids-based switch fluorescence biosensors over the years 2013 to 2020. Most of them have been proposed to the in vitro detection of different types of analytes, showing their wide scope and applicability, such as deoxyribonucleic acid (DNAs), ribonucleic acid (RNAs), proteins, enzymes, antibiotics, and heavy metal ions. Besides, some of them have also been applied to the bioimaging of intracellular analytes, emerging their potential for biomedical applications, for example, cellular adenosine triphosphate (ATP) and subcellular glutathione (GSH). Finally, the remaining challenges in this sensing field and prospects for future research trends are addressed. Graphical abstract.

CRISPR-Cas9 Triggered Two-Step Isothermal Amplification Method for E. coli O157:H7 Detection Based on a Metal-Organic Framework Platform.

Escherichia coli O157:H7 has been reported as an important pathogenic bacteria causing serious infection and economic loss. However, detection of Escherichia coli O157:H7 needs improvement, given its current complexity and sensitivity. Herein, we attempt to build a fluorescence sensing method to detect Escherichia coli O157:H7 with easy operation and high efficiency. The target virulence gene sequences are recognized and cleaved by the CRISPR-Cas9 system, and trigger strand displacement amplification and rolling circle amplification. After amplification reactions, massive products can hybridize with the probes, the fluorescence of which are quenched based on a metal-organic framework platform, leading to the fluorescence recovery at typical excitation/emission wavelengths of 480/518 nm. This method exhibits high sensitivity with the detection limit at 4.0 × 101 CFU mL-1 and a wide range from 1.3 × 102 CFU mL-1 to 6.5 × 104 CFU mL-1. Meanwhile, this assay also shows significant specificity and applies to practical samples with high accuracy. Therefore, our method would have great potential application in bacterial detection, food safety monitoring, or clinical diagnostics.

Bio-barcode triggered isothermal amplification in a fluorometric competitive immunoassay for the phytotoxin abrin.

Abrin is one of the most toxic phytotoxins to date, and is a potential biological warfare agent. A bio-barcode triggered isothermal amplification for fluorometric determination of abrin is described. Free abrin competes with abrin-coated magnetic microparticles (MMP) probes to bind to gold nanoparticle (AuNP) probes modified with abrin antibody and bio-barcoded DNA. Abundant barcodes are released from the MMP-AuNP complex via dithiothreitol treatment. This triggers an exponential amplification reaction (EXPAR) that is monitored by real-time fluorometry, at typical excitation/emission wavelengths of 495/520 nm. The EXPAR assay is easily operated, highly sensitive and specific. It was used to quantify abrin in spiked commercial samples. The detection limit (at S/N = 3; for n = 6) is 5.6 pg·mL-1 which is considerably lower than previous reports. This assay provides a universal sensing platform and has great potential for determination of various analytes, including small molecules, proteins, DNA, and cells. Graphical abstract Schematic representation of the bio-barcode triggered exponential amplification reaction (EXPAR) for a fluorometric competitive immunoassay for abrin. The limit of detection is 5.6 pg mL-1 with a large dynamic range from 10 pg mL-1 to 1 µg mL-1.

A low-field nuclear magnetic resonance DNA-hydrogel nanoprobe for bisphenol A determination in drinking water.

A low-field nuclear magnetic resonance (LF-NMR) DNA-hydrogel (LNDH) nanoprobe was designed for bisphenol A (BPA) determination. It consists of Fe3O4 superparamagnetic iron oxide nanoparticles (SPIONs) and a DNA-hydrogel technology. Fe3O4 SPIONs were encapsulated in the DNA-hydrogel to form an aggregated state. After adding BPA, the gel system transformed into a sol gel due to the target-aptamer specific binding. The coated gathered particles dispersed and thus, the relaxation time T2 declined. The LNDH nanoprobe was developed to realize a simple, sensitive, and effective BPA determination method without repeated magnetic separation steps. Under the optimal experimental conditions, the determination range of the LNDH biosensor was 10-2~102 ng mL-1 and the limit of determination was 0.07 ng mL-1. The LNDH nanoprobe was applied to two kinds of water samples (tap water and bottled water). The recovery ranged from 87.85 to approximately 97.87%. This strategy offered a new method to detect BPA by LF-NMR. It is also expected to be applicable in related fields of food safety determination, environmental monitoring, and clinical diagnosis. Graphical abstract Schematic presentation of LNDH biosensor. Acrydite-modified ssDNA was copolymerized with acrylamide to form linear conjugates PS-A/B, adding aptamer and SPIONs to form DNA-hydrogel. When aptamer captured the target, the hydrogel was destroyed to disperse the coated SPIONs. T2 relaxation time declined.

An ultrasensitive sensor based on quantitatively modified upconversion particles for trace bisphenol A detection.

Bisphenol A (BPA) is one of the endocrine-disrupting chemicals which might cause reproductive and endocrine system diseases, and poses a serious threat to the ecosystem and human health. This paper reports an ultrasensitive sensor for trace BPA detection employing fluorescence resonance energy transfer (FRET) between modified upconversion nanoparticles (UCNPs) and tetramethylrhodamine. To circumvent the problems of low luminous efficiency of FRET and low sensitivity of sensor, the upconversion nanoparticles with very strong fluorescence efficiency were prepared and quantitatively modified. Results showed that the concentrations of amino groups and streptavidin were 43 nmol/mg and 6.12 µg/mg on the surface of the UCNPs, respectively. Under the optimal detection conditions, the peak intensity of UCNPs at 547 nm was linear with the logarithm of the BPA concentration with the detection limit of 0.05 ng/mL. Without complicated pre-processing, the recoveries were in general between 91.0 and 115.0% in tap water, river water, and disposable paper cup water. Therefore, the proposed sensor is suitable for effective sensing of trace BPA in water samples. Graphical abstract ᅟ.

An aptamer-based fluorometric zearalenone assay using a lighting-up silver nanocluster probe and catalyzed by a hairpin assembly.

An enzyme-free fluorometric assay is described for the determination of zearalenone (ZEN). The method combines (a) catalyzed hairpin assembly (CHA), (b) ultrahigh fluorescent light-up G-rich DNA sequences in proximity to silver nanoclusters (Ag NCs), and (c) the use of aptamers (Apt). In the presence of ZEN, the inhibit sequence (Inh) is released from the aptamer-trigger sequence (Apt-T) via the binding of ZEN and the aptamer of Apt-T. The free Apt-T acts as a switch that opens the hairpins H1 and H2 to generate H1-H2 complex. The released Apt-T is available to trigger the next round of CHA between H1 and H2. Finally, the hybridization between H1 and the Ag NCs probe (P) causes the G-rich sequence to be in close proximity to the dark Ag NCs encapsulated by P. This leads to highly efficient lighting up of the Ag NCs and the production of amplified fluorescence with excitation/emission peaks at 575/628 nm. Under the optimized conditions, a linear correlation was observed with concentrations ranging from 1.3 pg mL-1 to 100 ng mL-1, and the limit of detection was 0.32 pg mL-1 (at S/N = 3). The method was successfully validated by analyzing maize and beer for levels of ZEN after a simple sample preparation procedure. Graphical abstractSchematic of the assay. The inhibit sequence (Inh) is released from aptamer-trigger sequence (Apt-T) via binding of ZEN and aptamer. The free Apt-T triggers catalyzed hairpin assembly (CHA).G-rich DNA is in proximity to silver nanoclusters (Ag NCs) and fluorescence intensity increases to detect ZEN.

Competitive fluorometric assay for the food toxin T-2 by using DNA-modified silver nanoclusters, aptamer-modified magnetic beads, and exponential isothermal amplification.

The authors describe an aptamer based assay for the mycotoxin T-2. The method is making use of exponential isothermal amplification reaction (EXPAR) and fluorescent silver nanoclusters (AgNCs). Free T-2 and cDNA (which is a DNA that is partially complementary to the aptamer) compete for binding to aptamer-modified magnetic beads. The cDNA collected by magnetic separation can be used as a primer to trigger EXPAR to obtain ssDNA. The C-base-rich ssDNA binds and reduces Ag(I) ion to form fluorescent AgNCs. Fluorescence is measured at excitation/emission wavelengths of 480/525 nm. T-2 can be detected by fluorometry with a detection limit as low as 30 fg·mL-1. The method was applied to analyse spiked oat and corn, and the average recoveries ranged from 97.3 to 102.3% and from 95.9 to 107.5%, respectively. The results were in good agreement with data of the commercial ELISA kit. The assay is highly sensitive, has a wide analytical range, good specificity and reliable operation. It provides a promising alternative for the standard method for quantitative detection of T-2. Graphical abstract Schematic presentation of fluorometric assay for T-2 based on aptamer-functionalized magnetic beads exponential, isothermal amplification reaction (EXPAR) and fluorescent silver nanoclusters (AgNCs).

Correction to: An aptamer-based fluorometric zearalenone assay using a lighting-up silver nanocluster probe and catalyzed by a hairpin assembly.

The published version of this article, unfortunately, contains an error regarding authors for correspondence.

Upconversion fluorescent aptasensor for bisphenol A and 17ß-estradiol based on a nanohybrid composed of black phosphorus and gold, and making use of signal amplification via DNA tetrahedrons.

This study describes an upconversion fluorescent aptasensor based on black phosphorus nanohybrids and self-assembled DNA tetrahedrons dual-amplification strategy for rapid detection of the environmental estrogens bisphenol A (BPA) and 17ß-estradiol (E2). Tetrahedron complementary DNAs (T-cDNAs) were self-assembled in an oriented fashion on a 2D nanohybrid composed of black phosphorus (BP) and gold to give a materials of architecture BP-Au@T-cDNAs. In parallel, core-shell upconversion nanoparticles were modified with aptamers (UCNPs@apts) and used as capture probes. On complementary pairing, the BP-Au@T-cDNA quench the fluorescence of UCNPs@apts (measured at an excitation wavelength 808 nm and at main emission peaks at 545 nm and 805 nm.) Compared with single-stranded probes based on black phosphorus and gold, the dual-amplification strategy increases quenching efficiency by nearly 25%-30% and reduces capture time to 10 min. This is due to the higher optical absorption of 2D nanohybrid and the reduction of steric hindrance by T-cDNAs. Exposure to BPA or E2 cause the release of UCNPs@apts from the BP-Au@T-cDNAs due to stronger binding between aptamer and analyte. Hence, fluorescence recovers at 545 nm for BPA and 805 nm for E2. Based on these findings, a dually amplified aptamer assay was constructed that covers the 0.01 to 100 ng mL-1 BPA concentration range, and the 0.1 to 100 ng mL-1 E2 concentration range. The detection limits are 7.8 pg mL-1 and 92 pg mL-1, respectively. This method was applied to the simultaneous determination of BPA and E2 in spiked samples of water, food, serum and urine. Graphical abstract Schematic presentation of novel quenching probes designed by tetrahedron complementary DNAs oriented self-assembled on the surface of black phosphorus/gold nanohybrids. Combined with aptamer-modified upconversion nanoparticles, a dual-amplification self-assembled fluorescence nanoprobe was constructed for simultaneous detection of BPA and E2.

Michael-Addition-Mediated Photonic Crystals Allow Pretreatment-Free and Label-Free Sensoring of Ciprofloxacin in Fish Farming Water.

Abuse of antibiotics results in a large number of antibiotics residues in the environment and even causes the problem of "super bacteria". Therefore, it is crucial to develop a powerful analytic method to monitor antibiotics quickly and simply. Photonic crystal (PC), as a sensing material, has promising application prospects. Herein, we try to use PC to realize pretreatment-free and label-free detection of Ciprofloxacin (CF) through Michael addition reaction. The recognition process is carried out by the Michael addition reaction between the piperazine group of CF and the o-benzoquinone group on the PC. The monodisperse microspheres with o-benzoquinone groups are prepared by polymerization and oxidation and then stacked to form PC. During the detection, the peak intensity of the PC decreases with the increasing CF concentration, and the linear range is from 2 to 512 µg/L. The limit of detection (LOD) is 0.76 µg/L. Furthermore, the PC retains 97% of the initial response after storage in a Petri dish at room temperature for 1 month, which shows that it has good stability. Moreover, CF in fish farming water can be detected directly without any pretreatment and label, and the results are in good accordance with the LC-MS-MS results. This Michael-addition-mediated PC is accurate, easily prepared, cost-efficient, and long-term stable. In addition, it is environmentally friendly, because little organic solvent is needed during both the preparation and the detection.

Upconversion Fluorescent Aptasensor for Polychlorinated Biphenyls Detection Based on Nicking Endonuclease and Hybridization Chain Reaction Dual-Amplification Strategy.

A novel upconversion fluorescent aptasensor based on hybridization chain reaction and nicking endonuclease has been developed for detection of polychlorinated biphenyls (PCBs). It combined the dual advantages of UCNPs and HCR. Two harpins (H1 and H2) were first designed according to the partial complementary sequence (cDNA) of the PCB72/106. Since the aptamer specifically recognized the target, the cDNA was detached from the magnetic microspheres (MMPs). The cDNA could initiate hybridization chain reaction (HCR) and open the stems of H1 and H2. After the addition of nicking endonuclease, UCNPs were further away from the quenchers (BHQ-1). Hence, the fluorescence intensity of upconversion nanoparticals (UCNPs) could be restored via fluorescence resonance energy transfer (FRET). Therefore, the fluorescence of UCNPs was directly proportional to concentration of PCB72/106, which was the basis for the quantification of PCB72/106. PCB72/106 could be analyzed within the ranges of 0.004 to 800 ng/mL with a detection limit of 0.0035 ng/mL ( S/ N = 3). The aptasensor was also used for the detection of water and soil samples, and the average recoveries ranged from 93.4% to 109.7% and 83.2% to 118.5%, respectively. The relative standard deviations (RSDs) were all below 3.2%. The signal was first amplified through HCR and further amplified with the help of nicking endonuclease. This work also provided the opportunity to develop fluorescent aptasensors for other targets using this dual-amplification strategy.

Turn-on fluorometric immunosensor for diethylstilbestrol based on the use of air-stable polydopamine-functionalized black phosphorus and upconversion nanoparticles.

The preparation of air-stable black phosphorus (BP) is challenging because atomic layers of BP degrade rapidly on exposure to oxygen. A strategy is presented for the synthesis of BP functionalized with polydopamine (PDA/BP). Dopamine was self-polymerized to yield polydopamine (PDA) which then was used to coat the surface of BP. PDA can be easily reduced and this prevents BP degradation. PDA/BP also is a viable matrix for the adsorption of proteins due to the presence of functional groups. Without any chemical activation, diethylstilbestrol (DES)-specific monoclonal antibody was adsorbed on the PDA/BP surface. PDA/BP quenches the fluorescence antigen-modified NaYF4:Yb,Ho,Nd upconversion nanoparticles (UCNPs; photoexcited at 808 nm) via specific immuno recognition. Exposure to DES causes the dissociation of UCNP from the PDA/BP surface and fluorescence at 475, 525, 545 and 660 nm to recover. This is due to the DES competition with antigen for binding to the antibody. Based on this competitive immuno mechanism, a turn-on fluorometric immunoassay was constructed. It has a response that covers the 0.1 to 1000 ng mL-1 DES concentration range with a detection limit of 83 pg mL-1. This method was successfully applied to the determination of DES in spiked food and human urine samples. Graphical abstract Air-stable polydopamine-functionalized black phosphorus was obtained by modification of black phosphorus with polydopamine and then was coupled with specific monoclonal antibody. Combined with antigen-modified upconversion nanoparticles, a turn-on fluorometric immunoassay was constructed to detect diethylstilbestrol.

[Rapid detection of diethylstilbestrol using a quartz crystal microbalance with gold nanoparticals amplification].

OBJECTIVE: To develop a quartz crystal microbalance (QCM) immunosensor with high sensitivity and selectivity for the rapid detection of diethylstilbestrol. METHODS: Dextran was used as reducing agent for preparing gold nanoparticles (AuNPs) with the size of 40 nm. The AuNPs were coupled with anti-DES antibody after amination. A monolayer was generated after immersing the quartz crystal into the solution of 5 mmol/L 11-mercaptoundecanoic acid(MUA) for 16 hours. After the monolayer was activated by 1-ethyl-3-(3-dimethylaminopropry) carbodiimide hydrochloride (EDC·HCl) and N-hydrosuccinimide (NHS), 20 µl of 2.2 mg/ml DES-HS-BSA was dropped onto the surface of crystal to prepare a sensitive membrane which can recognize DES specifically. Then, 50 µl of 1 mol/L ethanolamine (pH 8.5) was used to seal the carboxylic groups to make the sensitive membrane which could identify DES specifically. QCM immunosensor was used as detection platform to optimize the reaction conditions. Under the optimized conditions, 10 µl of 28 µg/ml AuNPs-antibody was mixed with 10 µl of 0.03-2.5 µg/ml DES, and the mixture was added on the sensitive membrane. QCM immunosensor was used to detect the signals and the standard curve was obtained at the same time. The detection limit was calculated based on the standard curve. The specificity was evaluated by testing DES and its analogues with the same concentration. RESULTS: The optimized concentration for the immobilization of DES-HS-BSA on the surface of QCM was 2.2 mg/ml. The optimized concentration for coupling anti-DES antibody with AuNPs was 7 µg/ml and 15 nmol/L, respectively. The optimized concentration of AuNPs-antibody was 14 µg/ml. The logarithm of DES concentration was proportional to the frequency shift in the range of 0.16-500 ng/ml, Δf=-24.170 lgCDES+69.71, R(2)=0.998. The detection limit of this method was 0.13 ng/ml. DES analogues could not influence the detection of DES obviously, so the sensor had good specificity. CONCLUSION: The quartz crystal microbalance immunosensor with gold nanoparticals amplification could detect DES sensitively and rapidly.

Selection of bisphenol A - single-chain antibodies from a non-immunized mouse library by ribosome display.

Developing reagents with high affinity and specificity are critical to detect the environmental hormones or toxicants. Ribosome display technology has been widely used in functional protein or peptide screening and in directed evolution of protein molecules in vitro. In this study, single-chain variable fragments (scFvs) against bisphenol A (BPA) were selected from a library constructed from splenocytes of non-immunized mice. After five rounds of selection, the selected scFvs bound to BPA with high affinity. Indirect competitive enzyme-linked immunosorbent assay (ELISA) was introduced to screen the antibody affinity and specificity to BPA. The equilibrium dissociation constants (KDS) of one clone was 1.76µM as determined by surface plasmon resonance (SPR). This study indicated that ribosome display can isolate binders to small molecules from a non-immunized naive library without any in vivo steps and can generate recombinant antibodies efficiently and rapidly. In addition, this study provides a methodological framework for detection of small molecules using recombinant antibodies.