An ultrasensitive sandwich-type electrochemical aptasensor using silver nanoparticle/titanium carbide nanocomposites for the determination of Staphylococcus aureus in milk.

A novel sandwich-type electrochemical aptasensor for the detection of Staphylococcus aureus (S. aureus) was developed. S. aureus aptamers were self-assembled onto the surface of a glassy carbon electrode (GCE) modified with nanocomposites comprising titanium carbide embedded with silver nanoparticles (AgNPs@Ti 3 C 2 ) through hydrogen bonds and the chelation interaction between phosphate groups and Ti ions. In addition, the self-assembled aptamers were immobilized on CuO/graphene (GR) nanocomposites via π-π stacking interactions to serve as a signal probe. In the presence of the target S. aureus, the sandwich-type recognition system reacted on the surface of GCE, and the CuO/GR nanocomposites catalyzed the hydrogen peroxide + hydroquinone reaction producing a strong current response. Under the optimal experimental conditions, the current response of the aptasensor was linearly correlated with the concentration of S. aureus (52-5.2 × 10 7  CFU mL -1 ) with a low detection limit of 1 CFU mL -1 . The aptasensor displayed good repeatability and excellent selectivity for S. aureus detection. Moreover, this aptasensor was applied to the detection of S. aureus in cow, sheep, and goat milk samples, affording recoveries ranging from 92.64 to 109.58%. This research provides a new platform for the detection of pathogenic bacteria and other toxic and harmful substances in food.