A novel electrochemical aptasensor for serum dopamine detection based on methylene blue-integrated m-PdNFs signal material

In this work, an aptamer was used as an identifying molecule and a novel amplification strategy based on Ce-MOF and m-PdNFs-G4-MBs for the sensitive detection of dopamine (DA) is demonstrated. Notably, a novel dopamine aptamer with higher affinity and specificity was chosen, and the PdNF was functionalized with MB via embeddedness and surface decoration for enhancing the intensity of electrochemical signal. The synthesized m-PdNFs-G4-MBs nanocomposite not only acts as the electrochemical indicator but also to label single-stranded DNA (S2) to acquire signaling probes (m-PdNFs-S2-G4-MBs) as a nanocarrier. Besides, an -NH2 modified single-strand DNA (S1) is designed, and form an S1-AP double-strand by annealing reaction with aptamer (AP), then the S1-AP is fixed on the Ce-MOF surface, decorated on electrode. In the presence of DA, DA bind to the AP and S1 regain single-stranded structure. And then, the single-stranded S1 recognizes m-PdNFs-S2-G4-MBs and captures them, ultimately producing an enhanced electrical signal. Due to the extraordinary conductive performance of Ce-MOF and the signal amplification of m-PdNFs-S2-G4-MBs, the new detection platform achieves a minimum detection limit to 6 pmol/L for DA and with a good specificity. Prominently, the results obtained from our platform for serum DA detection are highly consistent with the UPLC-MS method. These results suggest that this new platform has the potential to provide a convenient and efficient tool for the diagnosis of multiple neurological disorders in the future. This work also provides a good strategy for the construction of other biomolecule sensors.