DNA aptamers selection and characterization for development of impedimetric aptasensor for Bacillus cereus at different growing stages

The physiology (membrane integrity, intracellular esterase and redox activity) of individual pathogenic bacteria is various in different growing phase, which has a profound significance for food safety testing and control. In this work, the aptamers against B. cereus in different growing phase was firstly selected based on whole bacterium-SELEX screening approach. Out of 32 candidate aptamers screened, aptamer B15 and B16 showed relatively high binding affinity with an apparent dissociation constant (Kd value) of 16.13 ± 4.98 nM and 20.67 ± 5.23 nM, respectively. A label-free impedance based aptasensor was further fabricated based on the screened aptamer, immobilized onto the GCE/Au surface. With the addition of B. cereus, the electron transfer process was prevented and exhibited a significant decrease in the electron-transfer resistance. Under optimal conditions, the fabricated aptasensor can achieve high sensitive detection of B. cereus as low as 10 cfu/mL. A satisfactory recovery of 90.5%–105.3% was achieved for the B. cereus detection in spiked milk samples, exhibiting its prospect in the sensitive detection of B. cereus in daily life.