title: A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe.
abstract: In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO(2)-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO(2) composite nanoparticles with a SiO(2) surface coating. Our results showed that CdSe/ZnS/SiO(2) composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that the method had higher sensitivity and could count bacteria in 3 x 10(2) CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence peak intensity (Y) and the total bacterial count (X) was established in the range of 3 x 10(2)-10(7) CFU/mL using the equation Y = 374.82X-938.27 (R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the conventional plate count method, and the standard deviation was satisfactory.
authors.affiliation: Department of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China. fuxin1129@hotmail.com
authors.forename: Xin
authors.initials: X
authors.lastname: Fu
authors.forename: Kelong
authors.initials: K
authors.lastname: Huang
authors.forename: Suqin
authors.initials: S
authors.lastname: Liu
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D015169:Colony Count, Microbial / Q000379:methods*; D005456:Fluorescent Dyes; D053758:Nanoparticles; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D013997:Time Factors; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D005456:Fluorescent Dyes; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D012822:Silicon Dioxide; C058667:cadmium selenide; C031238:zinc sulfide