A disposable electrochemical aptasensor using single-stranded DNA-methylene blue complex as signal-amplification platform for sensitive sensing of bisphenol A

A disposable and sensitive electrochemical aptasensor was developed based on a single-stranded DNA (ssDNA)-methylene blue (MB) complex for the determination of bisphenol A (BPA). BPA-specific aptamer, a ssDNA with hairpin structure, was immobilized on a low-cost plastic electrode and acted as both the bio-recognition element and the signal-amplification platform. MB was then intercalated into the aptamer and acted as the signaling probe. The intercalated MB was liberated upon interaction with BPA due to DNA conformational change, thereby resulting in the reduction of electrochemical response. The proposed sensors in the intermediate and final stages were carefully characterized. Under optimal conditions, a good linear relationship was presented with the logarithm of BPA concentrations in the range of 0.001-100 mu g/L, and a detection limit of 0.4 ng/L was obtained. This proposed sensor was applied to detect BPA in real samples and achieved satisfying results.