Target-induced aptamer displacement on gold nanoparticles and rolling circle amplification for ultrasensitive live Salmonella typhimurium electrochemical biosensing

Salmonella typhimurium (S. typhimurium) infection disease is harm to public through food have become a life-threatening problem stresses an urgent need for development of rapid, robust and cost-effective alternative technology to help control the spread of S. typhimurium. Herein, a simple and facile aptasensor has been developed for ultrasensitive determination of live S. typhimurium by combining target-induced aptamer displacement on gold nanoparticles (AuNPs) deposited electrode with rolling circle amplification (RCA). The heterogeneous recognition and specific binding of target S. typhimurium with aptamer, releasing the primer binding part, leading to anchoring multiple circular templates on the aptasensor surface. Then, the RCA reaction was initiated to produce massive long DNA molecules with multiple tandem-repeat sequences. These RCA products could hybridize with the biotinylated detection probes for enzyme-amplified electrochemical readout on the surface of the aptasensor. The designed electrochemical aptasensor showed very high sensitivity for S. typhimurium down to 16 CFU mL−1 with a wide linear detection range of 20 to 2 × 108 CFU mL−1, and exhibited remarkable signal amplification performance, acceptable reproducibility and low matrix effect. This proposed strategy presented a simple and facile platform towards ultrasensitive and handy bacterial detection, which would become an effective tool for microorganism detection in food safety, clinical diagnostics and even biological threats monitoring.