Aptamer biosensor for Streptococcus hemolyticus detection based on fluorescence quenching by gold nanoparticles

This study describes a nanodiagnostic method using specific aptamer and gold nanoparticles (AuNPs) to detect Streptococcus hemolyticus. In this assay, fluorescein(FAM) labeled single-stranded DNA (ssDNA) probe was hybridized with the complement aptamer sequences which immobilized on the surface of AuNPs, and the fluorescence was quenched by AuNPs. However, when the aptamer DNA specifically combined with S. hemolyticus, the quenched fluorescence was released. Therefore, fluorescent intensity could reflect the S. hemolyticus existence. When S. hemolyticus was tested through different bacteria dilutions, the linear analysis was used to calculate minimal S. hemolyticus CFU, which is 33 CFU/ml. Hence, this test provided methodological exploration for rapid and sensitive identification of S. hemolyticus using aptamer and AuNPs. This rapid, sensitive, stable and novel method could be applied widely in the clinical laboratory and the food supervisory department in the future.   Key words: Aptamer, fluorescence, gold nanoparticles, Streptococcus hemolyticus.