An ultrasensitive and rapid detection of trace antibiotics is imperative for food safety and public health. Herein, we present a ratiometric fluorescent sensing strategy based on an aptamer labeled ...with a fluorescent dye and a highly stable zirconium-porphyrin MOF (PCN-222) as a fluorescence quencher for the high-efficiency detection of chloramphenicol (CAP). PCN-222 exhibits a strong adsorption ability toward the dye-labeled aptamer through π-π stacking, electrostatic, hydrogen bond, and coordination interactions. Experimental and simulation studies confirm that PCN-222 demonstrates a high quenching efficiency via fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) processes. In the presence of CAP, dye-labeled aptamers are released from the PCN-222 surface, resulting in the recovery of fluorescence. This proposed biosensor allows the complete detection of CAP within 26 min. For ratiometric measurement, its detection limit is as low as 0.08 pg mL−1 with a wide detection range from 0.1 pg mL−1 to 10 ng mL−1. It is successfully applied to analyze CAP in milk and shrimp samples, and its results are consistent with those of the commercial ELISA kit. This biosensor not only enables the rapid, ultrasensitive, and highly specific detection of CAP but also reveals excellent universality and multiplexed analysis performance.
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•The strategy of fluorescence aptasensor for antibiotic detection was developed based on the very stable zirconium-porphyrin PCN-222 as a fluorescence quencher.•The quenching mechanism of PCN-222 towards FAM-aptamer was both FRET and PET processes with a high quenching efficiency.•The proposed biosensor fulfilled the rapid, ultrasensitive and selective detection of chloramphenicol.•The assay showed the potential and practical application for antibiotic detection in real food samples.
Microplastics are abundant in oceans, lakes, soils and even air, and can pose potential threats to human health through food or respiratory intake. Moreover, microplastics have synergistic toxicity ...to the body after absorbing organic pollutants. In this study, laser scanning confocal microscope and flow cytometry were used to observe the intake of colonic cancer Caco-2 cells to polystyrene plastic with five different particlesizes (300 nm, 500 nm, 1 μm, 3 μm, 6 μm). The uptake rates of microplastics with different particle sizes were 73%, 71%, 49%, 43%, and 30%, respectively. Then, High Performance Liquid Chromatography (HPLC) was used to analyze the adsorption differences of polystyrene plastic with different particle sizes to bisphenol A (BPA). Finally, the proliferation toxicity of polystyrene microplastics with different particle sizeson Caco-2 cells before and after adsorption of BPA was compared. MTT experiments confirmed that microplastics caused an increase in cytotoxicity. This result may be related to increased cellular oxidative stress and mitochondrial depolarization. This hypothesis has been confirmed in reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) assays because nanoscale microplastics cause a large amount of ROS on Caco-2 cells after microplastic exposure, and micron-scale microplastics cause a significant decrease in MMP. At the same time, nanoscale microplastics can cause further depolarization of mitochondria due to their large specific surface area adsorption of BPA, which leads to enhanced cytotoxicity of microplastics after BPA adsorption. The results of this study are of great significance in the evaluation of the safety of microplastics in the human body.
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•The proliferation toxicity of polystyrene microplastics with different particle sizes on Caco-2 cells was analyzed.•Microplastics of 300 nm, 500 nm and 6 μm size showed high toxicity to caco-2 cell activity compared with 1 μm and 3 μm.•With the increase of microplastics particle size, the oxidative stress in cells decreased.•Mitochondrial depolarization induced by microplastics with the size of 6 μm was more obvious than that at 300 nm.•The synergistic toxicity of nano-scale polystyrene and bisphenol A on caco-2 cells was more obvious.
With the development of society, physical activity has come to be an effective means by which people pursue good health to improve the quality of life. However, with the increase of intensity and the ...passage of time, exercise injury has become a hazard that can no longer be ignored. It is imperative to find effective ways to inhibit or reduce the negative effects of exercise. Mitochondria are important organelles involved in exercise and play an important role in exercise injury and prevention. Studies have found that exercise preconditioning and increased mitochondrial nutrition can effectively decrease mitochondrial damage after exercise. Against this background, some of the newest developments in this important field are reviewed here. The results discussed indicate that exercise preconditioning and supplement mitochondrial nutrition need to be increased to prevent exercise-related injuries.
In this study, sandwich chemiluminescent immunoassay (CLIA) for the detection of Staphylococcal enterotoxin B (SEB) was developed using nanobody–alkaline phosphatase (Nb–ALP) fusion protein. The ...SEB-binding nanobodies were obtained from a naïve phage-display library and the Nb–ALP fusion protein was constructed and obtained as a thermally stable and potentially effective substance for detecting antibodies in CLIA. The working range of the sandwich CLIA based on anti-SEB monoclonal antibodies (mAbs) and our fusion protein, Nb37–ALP, was 3.12–50.0 ng mL−1 with SC50 = 8.59 ± 0.37 ng mL−1. The limit of detection was 1.44 ng mL−1 according to the blank value plus 3 standard deviations. In order to understand the interaction of SEB and Nb37 in depth, the 3D structure of the SEB–Nb37 complex was constructed and verified by molecular modeling and the docking method. The results showed that the complementary-determining region 3 (CDR3) of Nb37 embedded itself in the opening generated by the major histocompatibility complex (MHC) and T-cell receptor- (TcR) binding sites of SEB, indicating that Nb37 may affect the recognition of SEB by MHC class Ⅱ molecules and the TcR. The arginine residue (Arg) 101, Arg102 and phenylalanine residue (Phe)103 of CDR3 in Nb37 may have contributed to specific binding to form six salt-bridges between these and SEB. In conclusion, in terms of their specificity and sensitivity, the obtained anti-SEB Nb–ALP appears to have the potential to replace chemically labeled probes for the detection of SEB.
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•Nanobodies that bind to SEB were isolated from a naïve library.•The molecular mechanism of nanobodies interacting with SEB was described.•Nb37–ALP has the potential to replace chemically-coupled detection antibodies.•Nb37–ALP was shown to be thermally stable and be able to be produced in large scale.•A quick and sensitive sandwich CLIA method for the detection of SEB was developed.
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.
Graphical abstract
► We established an immunochip for detecting multiple targets simultaneously and rapidly. ► The immunochip was applied in drinking water with six different mycotoxins spiked. ► It is visual and ...semiquantitatve for the immunochip to detect six mycotoxins. ► Due to diffusion and covalent couple, probes with good activity can be immobilized onto agarose-modified chips. ► Their detection limits are at the level of picogram or nanogram.
Mycotoxins are highly toxic contaminants in food, animal feed, and commodities. The study has developed an immunochip for quantifying the concentrations of six mycotoxins: aflatoxin B1, aflatoxin M1, deoxynivalenol, ochratoxin A, T-2 toxin, and zearalenone, which were added to drinking water. The complete antigens (Ags) of the mycotoxins were contact printed and immobilized onto agarose-modified glass slides with 12 physically isolated subarrays, based on the reaction of both diffusion and covalent bond. The optimal concentration of each antigen and antibody (Ab) was obtained using an Ag–Ab immunoassay. Based on the indirect competitive immunoassay for the simultaneous detection of six mycotoxins in one single chip, six standard curves with good logistic correlation (R2>0.97) were respectively plotted. The working ranges (0.04–1.69, 0.45–3.90, 20.20–69.23, 35.68–363.18, 0.11–1.81, and 0.08–7.47ng/mL, respectively) were calculated, as well as the median inhibitory concentrations (0.31±0.04, 1.49±0.21, 34.54±1.30, 134.06±11.75, 0.49±0.05, and 1.54±0.22ng/mL, respectively), when six mycotoxins were detected simultaneously. Finally, the recovery rates in drinking water generally ranged from 80% to 120% on the same chip, with an intra-assay coefficient of variation lower than 15%. We successfully established an immunochip for simultaneous detection of six mycotoxins within 4h, with advantages of using minimal samples and being visually semiquantitative with our naked eyes. In summary, the method could be developed on one single chip for detecting multiple contaminants in actual samples.
Mycotoxins are highly toxic contaminants in foodstuffs and feedstuffs. The study presents a novel suspension array technology for quantifying four mycotoxins, namely, aflatoxin B1, deoxynivalenol, ...T-2 toxin, and zearalenone, in corn and peanut. Using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, the complete antigens of the mycotoxins became attached to the microspheres with viable activity. The optimal concentrations of each antibody and biotin-rabbit anti-goat IgG were obtained through chessboard titration. The four mycotoxins were detected simultaneously and quantitatively in corn and peanut using indirect competitive immunoassay. Multi-channel standard curves with appropriate logistic correlation (R2>0.9819) were respectively plotted. The broad working ranges with three to four orders of magnitude were calculated, and limits of detection at the pg level were found to be better than those obtained using high-performance liquid chromatography. The recovery rates in the actual samples generally ranged from 80.16% to 117.65%, with an intra-assay coefficient of variation lower than 15%, which indicated high accuracy and repeatability. A suspension array method for the simultaneous detection of the four mycotoxins within 4h was successfully developed using minimal samples; the method was proven to have high throughput, flexibility, accuracy and reproducibility. The approach could detect multiple contaminants in actual samples.
► We established a new suspension array method for detecting multiple targets simultaneously and rapidly. ► Probes with good activity can be attached to the surface of microspheres by covalent couple. ► Their detection limits are at the level of picogram. ► The approach was applied in corn and peanut with four mycotoxins simultaneously spiked. ► The result of assay showed good correlation with that of HPLC in actual samples.
A reliable and sensitive kit for the rapid detection of melamine (Mel) was developed. The kit is based on gold nanoparticle (Au NP) probe and includes a standard colorimetric card. The Au NPs were ...prepared by sodium borohydride reduction and characterized by transmission electron microscopy, which revealed particle sizes of approximately 5 nm. The performance of the kit in terms of aggregation kinetics, cross-reactivity, anti-interference, and sample pretreatment was investigated. The standard colorimetric card was then fabricated by chromatic aberration of a series of standard Mel-spiked milk reacts with the 5 nm Au NPs. The working range of the kit is 1–120 mg/L, and its performance is visibly more rapid and reliable by comparison with the standard colorimetric card. As low as 1 mg/L of Mel levels in milk can be determined, with the assay taking only about 10 min, including sample pretreatment. The kit can be stored for a year at room temperature. Samples were also detected by the kit, yielding results close to those obtained by high-performance liquid chromatography/mass spectrometry. Thus, the kit is applicable to qualitative and semiquantitative field detection, as well as naked-eye screening without the aid of any instrumentation.
Listeria monocytogenes (LM) is a gram-positive food-borne pathogen, which can cause serious disease. Rapid screening plays an important role in the prevention and identification of LM to cause food ...poisoning. In this study, we describe a novel electrochemical immunosensor by self-assembled monolayers (SAM)-modified gold (Au) electrodes for the detection of LM. Mouse monoclonal antibody of LM was immobilized on the SAM through a stable acyl amino ester intermediate generated by the co-addition of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Then, a direct sandwich format was developed, in which a polyclonal antibody for LM was conjugated to horseradish peroxidase (HRP) as the enzyme label. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the stepwise assembly of the immunosensor. In the presence of H2O2, HRP catalyzes the oxidation of thionine, whose back electrochemical reduction was detected on an Au electrode at −0.3V for 200s with chronoamperometry measurements versus an Ag/AgCl reference electrode. The reaction conditions were optimized, such as antibody concentration, immune reaction time, activation time, and blocking time. Under optimized conditions, when the concentration of LM is ranging from 102 to 106CFU/ml, the response current which is obtained from the labeled HRP to thionine–H2O2 system and the amount of LM are linearly related (R2=0.9883). There was no need for sample pretreatment when applied to detect LM in milk. Compared with plate count assay, it was found that the relative error of two methods was lower than 8%. The sensor is a straightforward and reliable method for analysis of LM with a simple operation, sensitivity at a low cost.
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.
Nur77 mediated apoptosis in cells as a key factor activated the caspase-3 pathway by inhibiting the NF-κb/Bcl-2. Display omitted
•The toxicity of BPA in PC12 cells was modelled.•BPA exposure induces apoptosis and oxidative stress in PC12 cells.•Nur77 plays a vital role in BPA induced PC12 cells damage.
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