Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense

Chongqing, China

Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense

Chongqing, China

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Wang R.,Chongqing University | Xu Y.,Chongqing University | Xu Y.,National Center for International Research of Micro Nano System and New Material Technology | Xu Y.,Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense | And 4 more authors.
Analytical Methods | Year: 2014

CdSe/ZnS@SiO2-NH2 composite nanoparticles (FNPs) were proposed and used as fluorescent markers for bacteria detection. Salmonella typhimurium acted as representative sample in this paper. It was shown that hydrophobic CdSe/ZnS quantum dots (QDs) were incorporated into SiO2 spheres by using a self-modified reverse-microemulsion technique. FNPs could be successfully covalently conjugated with the bacteria by glutaraldehyde in a two-step strategy. A good linear relationship between the concentration of Salmonella typhimurium and fluorescence intensity was obtained in the range of 6.6 × 102 to 6.6 × 104 cfu mL-1, and the equation was I = 0.1331logC - 0.2017 with R2 = 0.9974. The detection limit was 3.3 × 102 cfu mL-1, and this method could be applied to other bacteria detection as well. In order to further reduce the detection limit and achieve better visual determination performance, an integrated dielectrophoresis (DEP) microfluidic chip and relative microsystem was established. The FNP-labeled bacteria could be enriched along the edges of interdigitated microelectrodes in the micro-channel by positive DEP and could be counted under the fluorescence microscope. This journal is © the Partner Organisations 2014.


Wang R.,Chongqing University | Xu Y.,Chongqing University | Xu Y.,National Center for International Research of Micro Nano System and New Material Technology | Xu Y.,Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense | And 2 more authors.
Analytical Methods | Year: 2015

In this study, a combination of carbon dots (CDs) and aptamers is proposed as a novel fluorescence probe for sensitive quantitative detection of Salmonella typhimurium. Carboxyl-modified CDs with better biocompatibility and monodispersity were prepared by a hydrothermal method using citric acid as carbon source. To ensure specificity, amino-modified aptamers were connected to the surface of CDs modified with carboxyl to form the carbon dot-aptamer complexes (CD-apt), which are of extremely high quantum yield (ca. 76%) and specificity. Salmonella typhimurium was taken as a representative sample for fluorescence detection, and incubation time and dosage of CD-apt were investigated. Under the optimized conditions, a linear relationship between concentration of Salmonella typhimurium and fluorescence intensity was obtained in the range of 103 to 105 cfu mL-1 using the equation I = 82.506:log:C - 203.17 with R2 = 0.9903, and the detection limit was down to 50 cfu mL-1 without any sample enrichment process. Significantly, the practicability of this method was validated by assaying Salmonella typhimurium in egg samples and tap water. The proposed method is promising for rapid and sensitive detection of other bacteria if suitable aptamers are chosen. This journal is © The Royal Society of Chemistry.

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