Abstract
Amyloid-β protein (Aβ) is an important biomarker and plays a key role in the early stage of Alzheimer’s disease (AD). Here, an ultrasensitive photoelectrochemical (PEC) sensor based on ZnO@polydopamine/Au nanocomposites was constructed for quantitative detection of Aβ. In this sensing system, the ZnO nanorod array decorated with PDA films and gold nanoparticles (Au NPs) have excellent visible-light activity. The PDA film was used as a sensitizer for charge separation, and it also was used for antibody binding. Moreover, Au NPs were loaded on the surface of PDA film by in situ deposition, which further improved the charge transfer efficiency and the PEC activity in visible light due to the localized surface plasmon resonance effect of Au NPs. Therefore, in ZnO@polydopamine/Au nanocomposites, a significantly enhanced photocurrent response was obtained on this photoelectrode, which provides a good and reliable signal for early detection of AD. Under the optimized conditions, the PEC immunosensor displayed a wide linear range from 1 pg/mL to 100 ng/mL and a low detection limit of 0.26 pg/mL. In addition, this PEC immunosensor also presented good selectivity, stability, and reproducibility. This work may provide a promising point-of-care testing method toward advanced PEC immunoassays for AD biomarkers.
Highlights
As a most prevalent type of dementia, Alzheimer’s disease (AD) is a fatal and irreversible neurodegenerative disorder, occurring mainly in aged people.(Evans, Funkenstein et al, 1989; Matthews, Arthur et al, 2013) massive effort has been made to cure this disease, there is still no efficient treatment for it
The Zinc oxide (ZnO)@PDA were further used for in situ deposition of Au nanoparticles (Au NPs) basing on the reducing action of PDA coating
In Figure 2C; Supplementary Figure S2B, various Au NPs are observed homogeneously adhering on the surfaces of ZnO@PDA
Summary
As a most prevalent type of dementia, Alzheimer’s disease (AD) is a fatal and irreversible neurodegenerative disorder, occurring mainly in aged people.(Evans, Funkenstein et al, 1989; Matthews, Arthur et al, 2013) massive effort has been made to cure this disease, there is still no efficient treatment for it. The PDA coating involving in the system is used as a multifunctional platform such as a sensitizer for enhancing the photo-toelectron conversion efficiency, a binder for antibody bonding, and a reductant for in situ Au deposition Both PDA film and Au NPs can enhance the light absorption and loading content of antibody. The as-synthesized ZnO-ITO were dipped into 20 mL of Tris–HCl solution (10 mM, pH 8.5) containing 25 mg dopamine and kept for 4 h at room temperature, followed by gently rinsing with DI water several times. The prepared ZnO@PDA-ITO were immersed into the solution and incubated for 60 min These were taken out and rinsed gently with DI water and stored at 4°C for use. The photocurrent response measurements of the working electrode were collected under light irradiation switching on and off every 10 s at the applied potential of 0.05 V
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