Sensitive quantification and visual detection of bacteria using CdSe/ZnS@SiO₂ nanoparticles as fluorescent probes

Abstract

CdSe/ZnS@SiO 2 -NH 2 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 SiO 2 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 Â 10 2 to 6.6 Â 10 4 cfu mL À1 , and the equation was I ¼ 0.1331 log C À 0.2017 with R 2 ¼ 0.9974. The detection limit was 3.3 Â 10 2 cfu mL À1 , 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.

A sensitive fluorescence method for detection of E. Coli using rhodamine 6G dyeing

“…The linear ranges fore E. coli , B. subtilis and S. aureus detection were 7.06 × 10 4 to 3.53 × 10 7 , 4.95 × 10 5 to 2.475 × 10 8 and 32.5 to 16250 cfu/mL respectively. Compared with other reported methods , this fluorescence method is sensitive, has a wide linear range and the reagents used are easily obtained.…”

“…Enzyme‐linked immunosorbent (ELISA) is a mature technology, but cost is high, and chromogenic reagents such as benzene are harmful to humans and to the environment. In recent years, new methods for detection of bacteria have included nucleic acid aptamer analysis , surface enhanced Raman scattering (SERS) spectroscopy , voltammetry , fluorescence spectroscopy , and biosensor method etc. Although these methods possess high sensitivity and good specificity, their use of complex procedures, high cost and the high requirement for technical staff are prominent concerns.…”

Nanoparticles for Signaling in Biodiagnosis and Treatment of Infectious Diseases

“…The conjugate between fluorescent nanoparticles and bacteria may be detected by fluorescence microscopy. The detection limit was 3.3 × 10 2 CFU/mL, and this method may be applied to the detection of other bacteria [ 63 ].…”

Test-System for Bacteria Sensing Based on Peroxidase-Like Activity of Inkjet-Printed Magnetite Nanoparticles

“…Such an interaction changes physicochemical properties of the latter [7,8]. For instance, Ag and Au nanoparticles can be used for surface-enhanced Raman scattering (SERS) [9], carbon nanotubes for potentiometry [10], carbon nanotubes for potentiometry [10], CdSe [11], and CdS [12] quantum dots in the fluorescence microscopy and other materials and methods have found their application in bacteria sensing as well [13,14].…”