Dual-ratiometric aptasensor for streptomycin detection based on the in-situ coupling of photoelectrochemical and electrochemical assay with a bifunctional probe of methylene blue

Abstract This work reports a dual-ratiometric aptasensor based on the in-situ coupling of photoelectrochemical (PEC) and electrochemical (EC) assay for streptomycin (STR) detection. The key point is to take advantage of methylene blue (MB) as a bifunctional probe to simultaneously produce photocurrent (IMB-PEC) and redox current (IMB-EC). MB serves as a bridge to couple PEC with EC assay in situ, offering a PEC&EC dual-mode sensing. The redox current of ferrocene (IFc-EC) is designed as reference signal. Based on this principle, the specific recognition of STR leads to the stripping of Fc-tagged aptamer, and triggers the hybridization chain reaction to construct DNA duplex capable of absorbing MB. Using IMB-EC/IFc-EC and IMB-PEC/IFc-EC as yardsticks, the aptasensor offers two sets of linear ranges, i.e., 1 × 10-11–1 × 10-5 M for IMB-EC/IFc-EC and 1 × 10-9–1 × 10-4 M for IMB-PEC/IFc-EC. The dual-ratiometric strategy endows the aptasensor with enhanced analytical performances compared with that of single-signal or single-ratiometric assay. Our work offers an efficient way to fabricate high-performance aptasensors, and MB-based dual-mode sensing may provide a right tool to study interactions between PEC and EC behaviors.