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Now showing items 1 - 2 of 2

  • A novel aptasensor for the colorimetric detection of S. typhimurium based on gold nanoparticles

    Ma, Xiaoyuan   Song, Liangjing   Zhou, Nixin   Xia, Yu   Wang, Zhouping  

    A simple, fast and convenient colorimetric aptasensor was fabricated for the detection of Salmonella typhimurium (S. typhimurium) which was based on the color change effect of gold nanoparticles (GNPs). S. typhimurium is one of the most common causes of food-associated disease. Aptamers with specific recognition toward S. typhimurium was modified to the surface of prepared GNPs. They play a role for the protection of GNPs from aggregation toward high concentrations of NaCI. With the addition of S. typhimurium, aptamers preferably combined to S. typhimurium and the protection effect was broken. With more S. typhimurium, more aptamers detached from GNPs. In such a situation, the exposed GNPs would aggregated to some extent with the addition of NaCI. The color changed from red, purple to blue which could be characterized by UV-Vis spectrophotometer. The absorbance spectra of GNPs redshifted constantly and the intensity ratio of A700/A521 changed regularly. This could be calculated for the basis of quantitative detection of S. typhimurium from 102 cfu/mL to 107 cfu/mL. The obtained linear correlation equation was y =3D 0.1946x-0.2800 (R-2 =3D 0.9939) with a detection limit as low as 56 cfu/mL. This method is simple and rapid, results in high sensitivity and specificity, and can be used to detect actual samples.(C) 2017 Elsevier B.V. All rights reserved.
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  • SERS aptasensor detection of Salmonella typhimurium using a magnetic gold nanoparticle and gold nanoparticle based sandwich structure

    Ma, Xiaoyuan   Liu, Ying   Zhou, Nixin   Duan, Nuo   Wu, Shijia   Wang, Zhouping  

    A detection method for Salmonella typhimurium (S. typhimurium) using a surface-enhanced Raman scattering (SERS)-based sandwich structure was investigated. The biosensor was built on the basis of nanoparticle enhanced Raman intensity and the specific recognition of aptamers. Aptamer-functionalized magnetic gold nanoparticles (MGNPs) were used as the capture probe, while the aptamer and mercaptobenzoic acid (4-MBA) functionalized gold nanoparticles (GNPs) were used as the Raman signal probe. When S. typhimurium is added in the reaction system, the capture probe will capture the target bacteria through the specific binding effect of the aptamer. And then the signal probe will be connected to the bacteria also by the effect of the aptamer to form a sandwich-like detection structure. 4-MBA exhibits a specific peak at 1582.71 cm(-1). Under the optimal conditions, the SERS intensity exhibits a good linear relationship (y =3D 548.3039 + 783.9842x, R-2 =3D 0.9968) with the concentration of S. typhimurium ranging from 10 cfu mL(-1) to 107 cfu mL(-1). The LOD is 5 cfu mL(-1). This method is simple and rapid, results in high sensitivity and specificity, and can be used to detect actual samples.
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