Aptamer-functionalized magnetic beads combined with hybridization chain reaction for detection of Bacillus cereus

Based on the specific aptamer-functionalized magnetic beads and the hybrid chain reaction (HCR), a rapid detection method for Bacillus cereus was established. B. cereus competes with carboxylfluorescein-labeled cDNA (FAM-cDNA) to bind to biotin-labeled aptamer fixed on streptavidin magnetic beads. After magnetic separation, the released FAM-cDNA was used as an initiator to trigger HCR amplification, significantly enhancing the fluorescence signal. In the absence of B. cereus, the initiator binds to the aptamer, generating only a weak fluorescent signal. More importantly, graphene oxide (GO) can quench the fluorescence of unreacted FAM-cDNA, achieving a more accurate detection effect and thus enabling the detection of B. cereus at lower concentrations. This method has good specificity and can detect B. cereus as low as 5.4×10¹ CFU/mL. A linear response was observed across the concentration range of 5.4×10⁵ CFU/mL-5.4×10¹ CFU/mL. The feasibility of this method was verified by detecting B. cereus in artificially contaminated milk samples.