Detection of Escherichia coli in drugs with antibody conjugated quantum dots as immunofluorescence probes.

Based on outstanding optical properties of quantum dots (QDs), a rapid and specific method was established to determine Escherichia coli (E. coli) in drugs. Rabbit anti-goat antibody was covalently conjugated to water-soluble ZnS/CdSe QDs via a cross-linking reaction and the formed conjugate was named as IgG-QDs. The bio-fluorescent probe was verified using agarose gel electrophoresis. Attributing to the affinity between goat anti-E. coli antibody and rabbit anti-goat antibody, E. coli was bio-labeled by IgG-QDs successfully, which was then contributed to detecting E. coli in drugs specifically. The results demonstrated that bioactivity and biorecognition of the antibody was not influenced by the conjugation reaction and IgG-QDs could recognize E. coli specifically. Cell recovery rates for E. coli in clomipramine hydrochloride were 82.90% and 73.64%, respectively. The entire detecting process only spent less than 4h. The method was proved to be rapid and specific, and it could be used to detect stressed and injured cells.