As amyloid-β peptide 1–42 (Aβ42) was found to be an emerging and important biomarker for Alzheimer's disease, the detection of this peptide in biological samples such as human serum (HS) has become very important for evaluating the potential disease state and determining the appropriate treatment. In this study, we developed an electrical analysis strategy based on a field effect transistor (FET) biosensor as a simple and reliable technique for confirming the presence of Aβ42 aggregates (fibrils) in biological samples. By utilizing Congo red immobilized on the FET gate surface as a biorecognition element, we observed remarkable sensitivity and specificity for detecting Aβ42 fibrils. Furthermore, we optimized the procedure to minimize the interference of abundant human serum albumin for the detection system using HS samples. The optimized system of Congo red-immobilized FET enables measurement of Aβ42 fibrils in the 100-pM level in HS samples, which is lower than its clinical concentration. The FET device can be applied as a biosensing system for mass and routine screening of peptide biomarkers related to Alzheimer's disease.
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