Imaging Escherichia coli using streptavidin functionalized quantum dots as a Nano-fluorescent probe

It is extremely important for bacteria detection in many fields,such as medical diagnosis and food safety.In this paper,streptavidin functionalized quantum dots(SA-QDs),as a nano-fluorescent probe,were used to attach with Escherichia coli(E.coli) for the detection and identification of bacteria with immunoreactions and biotin-streptavidin affinity.Fluorescent images of the bacteria and the fluorescence intensity were used to evaluate the conjugation effect with different incubation time.Our results showed that 20 min is a reasonable incubation time for the SA-QDs coupling to E.coli cells.The fluorescent images,which produce a greatly amplified and enhanced signal of E.coli cells,were obtained through the immunological amplification and fluorescent probe enrichment steps.In addition,the bleaching process of SA-QDs without any encapsulation at room temperature was clearly observed during 10 min of being excited.Our work provided a modularized sample treatment method using SA-QDs as a nano-fluorescent probe in cellular imaging and bio-labeling.

It is extremely important for bacteria detection in many fields, such as medical diagnosis and food safety. In this paper, streptavidin functionalized quantum dots （SA-QDs） , as a nano-fluorescent probe, were used to attach with Escherichia coli （E. coli） for the detection and identification of bacteria with immunoreac- tions and biotin-streptavidin affinity. Fluorescent images of the bacteria and the fluorescence intensity were used to evaluate the conjugation effect with different incubation time. Our results showed that 20 rain is a reasonable incubation time for the SA-QDs coupling to E. coil cells. The fluorescent images, which produce a greatly am- plified and enhanced signal ofE. coli cells, were obtained through the immunological amplification and fluores- cent probe enrichment steps. In addition, the bleaching process of SA-QDs without any encapsulation at room temperature was clearly observed during 10 rain of being excited. Our work provided a modularized sample treatment method using SA-QDs as a nano-fluorescent probe in cellular imaging and bio-labeling.