Affinity peptide-based microfluidic electrochemical system for ultrasensitive detection of amyloid-β peptides.

The early diagnosis of Alzheimer's disease (AD) urgently requires analytical tools that simultaneously provide ultrahigh sensitivity, specific recognition, and fully automated operation to detect low-abundance amyloid-β (Aβ) peptides in peripheral blood. To address this challenge, an affinity peptide (AP)-based microfluidic electrochemical system (μF-APEC) was developed. As the core recognition elements in a sandwich assay, the APs were selected from a phage display library with a diversity of 100 billion variants, enabling high-affinity binding and precise recognition. By integrating the electrochemical biosensor with a microfluidic chip, the μF-APEC system enables automated sample injection, on-chip mixing, and electrochemical readout, with the entire detection process completed in less than 20 min. Under the optimized detection conditions, the system achieved ultrasensitive quantification, with limits of detection of 38 fg/mL for Aβ40 and 14 fg/mL for Aβ42, with a linear range of 100 fg/mL to 1 ng/mL. In serum samples, the μF-APEC system showed strong agreement with conventional enzyme-linked immunosorbent assay measurements and clearly distinguished AD patients from healthy individuals. By combining AP-based specific recognition with high sensitivity and automated operation, the μF-APEC system provides a robust and practical platform for the detection of low-abundance peripheral Aβ peptides, demonstrating its potential for the early screening of AD.