Abstract
The development of an electrochemical biosensor for the detection of phosphorylated-tau threonine 231 (p-tau231), a biomarker of Alzheimer’s disease (AD), has yet to be achieved. Therefore, in this study, we developed a simple, small size, cheap, and sensitive electrochemical biosensor based on an interdigitated wave-shaped electrode via an activated self-assembled monolayer to preserve a specific anti–p-tau231 antibody (IWE/SAM/EDC-NHS/anti–p-tau231). Detection of p-tau231 in human serum (HS) using the biosensor was undertaken using electrochemical impedance spectroscopy (EIS). The change in charge-transfer resistance (Rct) in the EIS analysis of the biosensor indicated the detection of p-tau231 in HS within a wide linear range of detection (10−4–101 ng mL−1), and a low limit of detection (140 pg mL−1). This lower limit is less than the detection level of p-tau231 in cerebrospinal fluid (CSF) (700 pg mL−1) of AD patients and the level of CSF p-tau231 of patients with mild cognitive impairment (501 pg mL−1), demonstrating the possibility of using the biosensor in detection of p-tau231 at early stage AD. A high binding affinity and low dissociation constant (Kd) between anti–p-tau231 and p-tau231 in HS was demonstrated by using a biosensor and Kd was 7.6 pM, demonstrating the high specific detection of p-tau231 by the biosensor. The good selectivity of the biosensor for the detection of p-tau231 with differential analytes was also examined in this study.
Highlights
Alzheimer’s disease (AD) is a continuing brain disorder and is a typical disease of dementia
A recent study of detection of p-tau231 in the cerebrospinal fluid (CSF) of patients with AD reported a high sensitivity of 85% and a specificity of 97% in separating AD from dementia with Lewy bodies and vascular dementia and indicated the appearance of p-tau231 in the early stages of pathology in patients with
In order to confirm the formation of self-assembled monolayer (SAM) on interdigitated wave-shaped electrode (IWE), AFM was used to characterize 3D topography and the roughness of the bare electrode and the electrode modified by SAM (Figure 2)
Summary
Alzheimer’s disease (AD) is a continuing brain disorder and is a typical disease of dementia. In the field of electrochemical detection, the advantages and importance of electrochemical biosensors for the determination of acceptable concentrations of biomolecules, drugs, and biomarkers have been reported recently because of their reliability, rapid response, high selectivity, and low cost [11,12,13,14,15,16,17,18,19,20,21]. In this study, we designed and fabricated an interdigitated wave-shaped electrode (IWE) with an electrode finger of 7 μm to avoid the effect of a concentrated electric field at the edge, to eliminate the Warburg diffusion impedance, and to enhance the homogeneity of the electrode sensing area, resulting in the improvement of the capabilities of the electrochemical biosensor in biomarker sensing. The selectivity of the developed biosensor for the detection of p-tau231 in the presence of various analytes was examined in this study
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