Design of a triple-functional polyA-probe: toward a facile electrochemical aptasensor for vanillin detection

This study successfully developed an electrochemical aptasensor based on a triple-functional biotin-modified poly-adenine (polyA) probe (Bio-TPP) for one-step ultrasensitive detection of vanillin (VAN). The Bio-TPP was self-assembled onto a gold electrode (AuE) via its polyA sequence, followed by conjugation with PtPd@Ni-Co layered double hydroxides labeled with streptavidin and thionine (SA/Thi/PtPd@Ni-Co LDH), which generated electrochemical signals. Importantly, in the presence of VAN, the specific substrate sequence of a Mg²⁺-dependent DNAzyme in the Bio-TPP hybridized with the output DNAzyme strand generated by the specific recognition between the aptamer (Apt) and VAN. And, with the help of Mg²⁺, the DNAzyme amplification reaction was triggered. This led to a significant reduction in the electrochemical signals, enabling highly sensitive detection of VAN. Benefiting from the precise and flexible design of the Bio-TPP, this aptasensor offered a new detection method, exhibiting excellent performance with a wide linear range of 1×10⁻⁶-10 μM and a detection limit of 0.30 pM. Additionally, this assay possessed good selectivity, reproducibility, and stability, which held great potential in bioanalysis.