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 TiO₂ nanobrush (TiO₂ NB). It is demonstrated that the control of the TiO₂ seed solution ratio, process temperature and duration significantly contributed to the final morphological characteristics of the rutile TiO₂ 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 TiO₂ 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 $\beta $ -amyloid ( $\text{A}\beta $ )_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 $\text{A}\beta _{\text {1-28}}$ peptides, the constructed TiO₂ NB photoelectrochemical (PEC) sensor exhibited a great sensitivity of $114.8\mu $ 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.