Hydrogel-Coated Gate Field-Effect Transistor for Real-Time and Label-Free Monitoring of β-Amyloid Aggregation and Its Inhibition.

In this paper, we propose a hydrogel-coated gate field-effect transistor (FET) for the real-time and label-free monitoring of β-amyloid (Aβ) aggregation and its inhibition. The hydrogel used in this study is composed of poly tetramethoxysilane (TMOS), in which Aβ monomers are entrapped and then aggregate, and coated on the gate insulator; that is, Aβ aggregation is induced in the vicinity of the sensing surface. With the Aβ hydrogel-coated gate FET, the steplike decrease in the surface potential of the Aβ hydrogel-coated gate electrode is electrically monitored in real time, according to the stepwise aggregation of Aβ monomers to form into fibrils through oligomers and so forth in stages. This is because the capacitance of the Aβ-hydrogel membrane decreases depending on the stage of aggregation; that is, the hydrophobicity of the Aβ-hydrogel membrane increases stepwise depending on the amount of Aβ aggregates. The formation of Aβ fibrils is also confirmed in the measurement solution using a fluorescent dye, thioflavin T, which selectively binds to the Aβ fibrils. Moreover, the addition of daunomycin, an inhibitor of Aβ aggregation, to the measurement solution suppresses the stepwise electrical response of the Aβ hydrogel-coated gate FET. Thus, a platform based on the Aβ hydrogel-coated gate FET is suitable for a simple screening system for inhibitors of Aβ aggregation, which may lead the identification of potential therapeutic agents for Alzheimer's disease.