A Photoelectrochemical Immunosensor Based on Au‐Doped TiO₂ Nanotube Arrays for the Detection of α‐Synuclein

Abstract

α-Synuclein (α-SYN) is a very important neuronal protein that is associated with Parkinson's disease. In this paper, we utilized Au-doped TiO(2) nanotube arrays to design a photoelectrochemical immunosensor for the detection of α-SYN. The highly ordered TiO(2) 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 TiO(2) nanotubes formed effective antibody immobilization arrays and immobilized primary antibodies (Ab(1)) with high stability and bioactivity to bind target α-SYN. The enhanced sensitivity was obtained by using {Ab(2)-Au-GOx} bioconjugates, which featured secondary antibody (Ab(2)) 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 H(2)O(2), which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of TiO(2) 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 50 pg mL(-1) to 100 ng mL(-1) with a detection limit of 34 pg mL(-1). The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for protein detection.

Research Trends in Doping Methods on TiO₂ Nanotube Arrays Prepared by Electrochemical Anodization

“…Nobel metals such as Ag and Au are frequently doped into TiO2 in order to increase the sensitivity of gas/bio sensing [32,33] and the others such as Si, CdS, Zr, Cr, Ni, Ru, W, etc. are classified as the catalysts for electrochemical or photoelectrochemical activator [25,[34][35][36][37][38][39][40][41][42][43][44][45][46].…”

Arrays of TiO2 Nanowires as Photoelectrochemical Sensors for Hydrazine Detection

“…Photoelectrochemistry has been extensively used in energy harvesting and environmental decontamination [9,10], but recently it has been proposed as a promising analytical tool [11][12][13][14][15][16][17][18][19]. Indeed this technique has been successfully applied for the determination of environmental pollutants [14][15][16][17] and biomolecules [11][12][13]18,19]. Photoelectrochemical analysis employs light as the excitation source and the response in photocurrent as the detection signal; thanks to the different forms of energy use for excitation and detection, this process reduces the background signal [15].…”

Nanotechnology platforms in Parkinson’s Disease

“…α-synuclein detection: As described earlier, α-Synuclein is a very important neuronal protein associated with PD and present day strategies for its quantitative detection include sophisticated, time-consuming instruments including NMR spectroscopy, fluorescence measurements, western blotting and size-exclusion chromatography [64]. An et al developed highly ordered microfabricated arrays using gold-doped TiO 2 nanotubes for photoelectrochemical detection of α-Synuclein [64].…”

“…An et al developed highly ordered microfabricated arrays using gold-doped TiO 2 nanotubes for photoelectrochemical detection of α-Synuclein [64]. The arrays were effective platforms for the immobilization of primary antibodies while retaining their stability and α-Synuclein binding [64].…”

“…Glucose oxidase catalyzed the conversion of glucose into gluconic acid and hydrogen peroxide. Upon irradiating the other side of the titanium foil, the holes that were formed within the valence band of the nanotubes could be scavenged by the peroxide leading to a photocurrent proportional to concentrations of α-Synuclein with a detection concentration in the range of pg/ml [64].…”