A photoelectrochemical immunosensor based on au-doped TiO₂ nanotube arrays for the detection of α-synuclein

α-Synuclein (α-SYN) is a very important neuronal protein that is associated with Parkinson's disease. In this paper, we utilized Au-doped TiO₂ nanotube arrays to design a photoelectrochemical immunosensor for the detection of α-SYN. The highly ordered TiO₂ nanotubes were fabricated by using an electrochemical anodization technique on pure Ti foil. After that, a photoelectrochemical deposition method was exploited to modify the resulting nanotubes with Au nanoparticles, which have been demonstrated to facilitate the improvement of photocurrent responses. Moreover, the Au-doped TiO₂ nanotubes formed effective antibody immobilization arrays and immobilized primary antibodies (Ab₁) with high stability and bioactivity to bind target α-SYN. The enhanced sensitivity was obtained by using {Ab₂-Au-GOx} bioconjugates, which featured secondary antibody (Ab₂) and glucose oxidase (GOx) labels linked to Au nanoparticles for signal amplification. The GOx enzyme immobilized on the prepared immunosensor could catalyze glucose in the detection solution to produce H₂O₂, which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of TiO₂ nanotubes upon irradiation of the other side of the Ti foil and led to a prompt photocurrent. The photocurrents were proportional to the α-SYN concentrations, and the linear range of the developed immunosensor was from 50pgmL^-1 to 100ngmL^-1 with a detection limit of 34pgmL^-1. The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for protein detection. The straight dope: Highly ordered Au-doped TiO₂ nanotubes were used to construct arrays that effectively immobilized primary antibodies with high stability and bioactivity to bind α-synuclein (see figure). Moreover, the Au-doped TiO₂ nanotubes facilitated the improvement of the photocurrent response.