Photoelectrochemical Detection of β-amyloid Peptides by a TiO2 Nanobrush Biosensor

A simple, facile and cost-effective nanostructuring technique is proposed to construct a photoelectrochemical (PEC) sensor via the solution-based hydrothermal growth of a TiO
₂
nanobrush (TiO
₂
NB). It is demonstrated that the control of the TiO
₂
seed solution ratio, process temperature and duration significantly contributed to the final morphological characteristics of the rutile TiO
₂
NB, as confirmed by the X-ray diffraction (XRD) analysis. By carrying out a simple and inexpensive fabrication involving no additional surface modification materials, the proposed TiO
₂
NB enabled the enhancement of the surface area by up to 162% in comparison with its actual geometric area. The photoactivity achieved by applying UV-range light was drastically improved, and photocurrents could potentially be utilized to enhance the redox activity on the interface. The system was used to detect β-amyloid (Aβ)
_1-28
peptides, one of the most crucial biomarkers of patients with Alzheimer's disease (AD), and demonstrated an excellent biocompatibility caused by the straightforward self-assembled monolayers (SAMs) modified on its surface. For the detection of a wide range of Aβ
_1-28
peptides, the constructed TiO
₂
NB photoelectrochemical (PEC) sensor exhibited a great sensitivity of 114.8 μ A/(ng
^.
mL
^-1
) and limit of detection (LoD) of 26.3 ng.mL
^-1
, facilitating a simple, label-free, rapid, sensitive and noninvasive method to overcome the limitations of conventional techniques used for AD diagnosis.