Photoelectrochemical Sensing of α-Synuclein Based on a AuNPs/Graphdiyne-Modified Electrode Coupled with a Nanoprobe.

We developed a method for photoelectrochemical (PEC) sensing based on a AuNPs/graphdiyne, as a low background signal composite material, modified electrode coupled with a nanoprobe (probe DNA/DA/MBA/WSe) for sensitive α-synuclein (α-Syn) detection. A tungsten selenide (WSe) nanoflower was first produced with a one-pot solvothermal method and employed as a signal amplification element and the modified substrate of the nanoprobe. The synergy effect between the WSe nanoflower and graphdiyne (GDY) can reduce the photoinduced electron-hole recombination and expedite the spatial charge separation. Due to the synergistic effect of AuNPs/GDY and WSe, this detection strategy provides a high signal-to-noise ratio and good performance. The signal indicator, dopamine/4-mercaptophenyl boronic acid/WSe (DA/MBA/WSe), was generated with the recognition of boron-diol. In the presence of the α-Syn oligomer, the target triggered cycle I strand displacement amplification and achieved the conversion of the α-Syn oligomer to a massive output of false-target DNA (FT). The output FT was used for the cycle II catalytic hairpin assembly onto the electrode which was modified with AuNPs/GDY and triple-stranded DNA (TsDNA); thereby, plenty of PEC nanoprobes which are composed of probe DNA and the signal indicator are captured, and the photocurrent response is produced correspondingly. This PEC biosensor generated a strong photocurrent with low blank (27.6 nA) and was sensitive to α-Syn oligomer. The limit of detection was 3.3 aM, and the relative standard deviation (RSD) was 3.7% at 100 aM. Moreover, it also has good selectivity, indicating promising potential in clinical diagnostics.