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Rapid and sensitive detection of foodborne pathogens is of great importance for food safety. Here, a set of nuclear magnetic resonance (NMR) biosensors based on a O-carboxymethyl chitosan target gadolinium (Gd) probe was developed to quickly detect Salmonella in milk by combining NMR technology and bioimmunotechnology with membrane filtration technology. First, O-carboxymethyl chitosan (O-CMC) was biotinylated to prepare biotinylated O-carboxymethyl chitosan (biotin–O-CMC) through amide reaction, and biotinylated magnetic complexes (biotin–O-CMC–Gd) were obtained by using O-CMC, which has strong chelating adsorption on Gd. The target probe was obtained by combining biotin–O-CMC–Gd with the biotinylated antibody (biotin–antibody) via streptavidin (SA) by introducing the SA–biotin system. Then, Salmonella was captured by the target probe through antigen–antibody interaction. Finally, NMR was used to measure the longitudinal relaxation time (T1) of the filtrate collected by membrane filtration. This NMR biosensor with good specificity and high efficiency can detect Salmonella with the sensitivity of 1.8 × 103 cfu/mL within 2 h; in addition, it can realize the detection of complex samples because of its strong anti-interference capability and may open up a new method for rapid detection of Salmonella, which has a great application potential. more...

Rapid and sensitive detection technology is the key to preventing food-borne disease outbreaks. In this study, a low-field nuclear magnetic resonance (NMR) biosensor based on polyamidoamine dendrimers was prepared for the rapid detection of Salmonella in milk. The polyamidoamine dendrimer was biotinylated by amide reaction and chelated to diethylene triamine pentacetate acid and gadolinium to form magnetic complexes. The antibody and magnetic complexes were combined through a streptavidin-biotin system using streptavidin as an intermediate bridge to obtain the immunoprobe. Salmonella was captured by the immunoprobe via antigen-antibody interaction and then separated from the mixture by membrane filtration. Finally, the longitudinal relaxation signal of the filtrate was obtained by NMR. The biosensor had excellent anti-interference capability and could detect Salmonella within 1.5 h at a sensitivity of 103 cfu mL-1. This method based on NMR can realize detection in complex samples and has the potential to be a quick and nondestructive method for detecting target bacteria. more...

Foods contaminated by foodborne pathogens have always been a great threat to human life. Herein, we constructed an electrochemical immunosensor for Salmonella detection by using a Fe

In order to study the synergistic effects of organic and inorganic thickening agents on the rheological properties of cement paste, the rheological parameters, thixotropy cement-paste containing limestone powder (LP), re-dispersible polymer powder (RPP), and hydroxypropyl methylcellulose ether (HPMC) were investigated using the Anton Paar MCR 102 rheometer at different resting times. The early-age hydration process, hydration products, and microstructure were also analyzed with scanning electron microscopy (SEM) and thermogravimetry analyses (TGA). The results showed that the addition of LP, RPP, and HPMC affected the rheological properties of cement paste, but the thickening mechanism between organic and inorganic thickening agents was different. The small amount of LP increased the plastic viscosity but decreased the yield stress of cement paste due to its dense filling effect. Adding 1% of RPP improved the thixotropic property of cement paste by 50%; prolonging the standing time could improve the thixotropic performance by as much as two times. Only 0.035% HPMC added to the cement paste increased the plastic viscosity by 20%, while the yield stress increased nearly twice. The more HPMC added, the more significant effect it showed. Cement paste compounds with LP, RPP, and HPMC balanced the yield stress and plastic viscosity and improved the thixotropy. The C-L6-R1.0-H0.035 paste presented as a pseudoplastic, its rheological indexes were close to one, and it was hardly affected by the resting time. The composite superposition effect of organic and inorganic thickening agents reduced the impact of resting time for all pastes. As the organic thickening component inhibited the hydration more than the LP promoted the hydration of the cement paste, indicating that the C-L6-R1.0-H0.035 paste remained in the particle fusion stage after curing for three days, as shown by the SEM images. more...

The presence of Salmonella in food has been a serious threat to human health all over the world. Herein, a novel electrochemical immunosensor based on CoFe-MOFs-graphene nanocomposite was constructed to detect Salmonella in milk. The synergy of the large specific surface area and high porosity of CoFe-MOFs and the good electrical conductivity of graphene materials greatly enhanced the current signal of the nanocomposite. Gold nanoparticles were modified on CoFe-MOFs-graphene hybrids by a simple electrodeposition method. Anti-Salmonella antibody was immobilized onto the surface of the constructed electrode through the formation of a stable Au–NH2 bond. Scanning electron microscopy was employed to reveal the structure of the CoFe-MOFs-graphene nanocomposite, and the elements of the nanocomposite were observed by energy-dispersive X-ray spectroscopy. In addition, Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) were used to analyze the structure of related materials. Under optimal experimental parameters, the constructed immunosensor detected a wide linear range of Salmonella from 2.4 × 102 CFU mL−1 to 2.4 × 108 CFU mL−1 with a detection limit of 1.2 × 102 CFU mL−1 (S/N = 3). The immunosensor showed good stability, selectivity, and reproducibility. The designed immunosensor provides a new strategy for the rapid detection of foodborne pathogens. more...

The growing threat of foodborne disease has made it imperative to develop rapid and efficient detection techniques. Here, we developed dendritic superparamagnetic iron oxide nanoparticles (SPIONs) combined with low-field nuclear magnetic resonance (LF-NMR) biosensor for Salmonella detection in milk. We first used a Salmonella capture antibody and biotinylated detection antibody (BT-mAb) in the form of a sandwich in a 96-well plate to immobilize target bacteria. Then streptavidin modified polyamidoamine (SA-PAMAM) was used to connect BT-mAb and functionally modified SPIONs. PAMAM-mediated SA amplified functionalized SPIONs via streptavidin-biotin amplification system, aggregated nanoparticles to form dendritic SPIONs, and achieved dual signal amplification. Finally, the dendritic SPIONs capture complex is eluted, and the lateral relaxation time T2 of the water molecules around the SPIONs was used as the output of the target bacteria capture signal. The limit of detection of Salmonella in a buffer solution and milk was 2.6 × 104 CFU/mL, and the LF-NMR biosensor showed good specificity and anti-interference properties. Therefore, this innovative detection platform can be used as a sensitive, fast, and efficient tool for detecting foodborne pathogens. more...

Nitrogen doped TiO2 (TiO2−xNx), one of the most promising visible-light photocatalytic materials, exhibits a low photocatalytic activity owing to the rapid recombination of photogenerated electrons and holes, which is caused by the isolated energy level of N 2p formed above the valence band of TiO2. To reduce the recombination of photogenerated charges and further improve the photocatalytic performance of TiO2−xNx, in this study, Fe(III) cocatalyst was loaded on the surface of TiO2−xNx photocatalyst by a simple impregnation method. It was found that after surface modification by Fe(III) cocatalyst, the photocatalytic performance of all the TiO2−xNx photocatalysts could be greatly improved for the decomposition of MO under visible-light irradiation. Especially, the Fe(III)/TiO1.981N0.019 photocatalyst showed the highest photocatalytic activity and its rate constant k was ca. 52.5 × 10−4 min−1, which is higher than that of the corresponding TiO1.981N0.019 photocatalyst (9.9 × 10−4 min−1) by a factor of 5.3 times. Based on the present experimental results, the Fe(III) was thought to be an effective cocatalyst to significantly improve the electron transfer from the conduction band of TiO2−xNx to the adsorbed oxygen, thus facilitating the rapid separation of photogenerated charges and greatly enhancing the photocatalytic activity. In addition, the direct interfacial charge transfer from the N 2p isolated energy level to Fe(III) cocatalyst can also contribute to the enhanced photocatalytic efficiency of TiO2−xNx. Considering the abundant Fe resources and its low cost, the Fe(III)-cocatalyst modification can be regarded as an effective approach for rational design and development of high-performance visible-light photocatalysts in practical applications. more...

PurposeThe purpose of this paper is to draw conclusions about China's agricultural integration (CAI) by looking back its processes stage by stage, discussing the problems related to CAI, in order to learn salutary lessons for the future of agricultural development, for the increase in rural income, and especially for the promotion of CAI.Design/methodology/approachThe paper comprises three stages: analyzing the process of CAI from the household responsibility system, to agricultural industrialization, until the stage of CAI led by farmers' co‐operatives; discussing the related practice together with literature; and historically proving that there is no better way to promote CAI than letting it be led by farmers' co‐operatives.FindingsThe paper finds that, the development of China's agricultural economic organizations is owing to CAI, and can be studied stage by stage; the process of CAI proves that it needs to be promoted as a new style led by farmers' co‐operative in order to increase rural income; literature review also gives eloquent proof of the above viewpoint; agricultural integration led by farmers' co‐operative should be taken as a better way to upgrade CAI and to increase rural income, for it can decrease the benefit disputes that usually happened in the former type of agricultural industrialization.Originality/valueThe obvious value of the paper is to show, by a historical review, a way to promote CAI and to increase farmers' income. A literature review finds these countermeasures comprehensively, historically, and theoretically. The information about CAI will be beneficial for people who are interested in the topic. more...