Electrochemical biosensor for rapid detection of bacteria based on facile synthesis of silver wire across electrodes

The early detection of bacteria is of critical importance in addressing serious public health problems. Here, an electrochemical biosensor for rapid detection of bacteria based on facile synthesis of silver wire across electrodes was constructed. High-variable region of 16S rRNA of bacteria was used as biomarker. Polymerase-free synthesis of silver wire was introduced into electrochemical signal transduction to improve the sensitivity of electrochemical detection. The construction biosensor of proposed method is as follows: Metastable hairpin probe H₁ was modified on electrode surface, biomarker can open the stem-loop structure of H₁ and activates HCR. The alternate opening of the stem-loop structure of H₁ and H₂-AuNPs finally results in the formation of long double-stranded DNA-RNA (HCR products) -AuNPs. The formed AuNPs modified HCR products was blown in one direction using N₂ to across the electrode gap. Using this HCR products as template, the silver wire was formed between the electrodes by silver deposition, and resulted in sharp change in electrical parameters of electrode. As the proof-of-concept work, multichannel series piezoelectric quartz crystal (MSPQC) was utilized as detector. The detection of Staphylococcus aureus in the concentration range from 50 to 10⁷ CFU/mL within 100 min was achieved. The detection limit was 50 CFU/mL. Escherichia coli, Salmonella enteritidis, Listeria innocua, Pseudomonas aeruginosa and Streptococcus pneumoniae did not interfere the detection results. This newly proposed electrochemical biosensor is simple, rapid and exhibit high signal-to-noise ratio, it has great potential for being applied in food safety monitoring and clinical diagnosis.