A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe.
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.
Fu
Xin
X
Department of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China. fuxin1129@hotmail.com
Huang
Kelong
K
Liu
Suqin
S
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
D019187:Cadmium Compounds; D005456:Fluorescent Dyes; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D012822:Silicon Dioxide; C058667:cadmium selenide; C031238:zinc sulfide