A bipolar Electrode-Electrochemiluminescence sensor for Salmonella typhimurium detection based on -cyclodextrin Host-Guest recognition

A bipolar electrode electrochemiluminescence (BPE-ECL) with beta-cyclodextrin (beta-CD) host-guest recognition was constructed for the rapid detection of Salmonella typhimurium (S. typhimurium). Firstly, the sulfhydryl beta-CD (SH beta-CD, with inner diameter size: 6.0-6.5 & Aring;) was assembled on the gold-plated cathode of BPE. Ferrocene (Fc, length: 3.5 & Aring;; width: 4.4 & Aring;) labelled signal probe and parts Fc-aptamer complement each other to form a double stranded DNA (dsDNA). Due to its large size, the dsDNA with a double Fc (width > 8.8 & Aring;) could not be embedded into the cavities of beta-CD. In the presence of S. typhimurium, Fc-aptamer bond specifically to S. typhimurium, and the signal probe was shed from the dsDNA. Then, the signal probe (guest) was captured by the SH-beta-CD (host) on the surface of the BPE. Due to the principle of spatial matching between Fc and SH-beta-CD, a stable inclusion complex could be formed, which made Fc close to the cathode surface of the BPE. When a certain driving voltage was applied, Fc was oxidized to Fc(+). The cathode surface of Fc(+) would promote electron transfer, causing the [Ru (bpy)3](2+) at the anode emit light, and effectively convert the electrochemical signal into an ECL signal. 10(1)-10(5) CFU mL(-1) S. typhimurium was positively correlated with Fc(+) and ECL intensity, with a detection limit of 101 CFU mL(-1). Therefore, S. typhimurium can be quantitatively detected by the electron transfer rate of the BPE.