Ultrasensitive electrochemical DNA sensor for virulence invA gene of Salmonella using silver nanoclusters as signal probe

This work described a sensitive electrochemical sensing method for detection of invA gene sequence of Salmonella by integrating direct signal inducer of silver nanoclusters (AgNCs) and cystine-rich (C-rich) signal probe DNA assembled gold nanoparticls (sDNA-AuNPs). Thiolated capture probe was covalently immobilized onto the glassy carbon electrode, and further hybridized with target DNA sequence (tDNA) and sDNA-AuNPs onto form a sandwich-type structure. The C-rich sDNA in the structure was then used as template for the formation of AgNCs, which can produce the direct voltametric signal during the detection of tDNA. Under optimal conditions, the fabricated biosensor showed good linearity from 1 fM to 0.1 nM with a detection limit of 0.162 fM ( S/N  = 3). It exhibited good selectivity, stability and reproducibility and can be applied to detect Salmonella effectively by detecting the polymerase chain reaction products of invA gene.