Amplification of electrochemical signal by moving interdigitated electrode array for highly sensitive detection of Alzheimer's disease markers in blood.

Electrochemical biosensors are widely utilized in disease diagnosis due to their high sensitivity, low detection limits, and cost-effectiveness. However, conventional electrochemical ELISA (e-ELISA) measurements face several challenges and limitations, including limited analyte volume, reduced sensitivity, signal instability, and surface fouling. To overcome the limitations, we developed a novel vertically moving sensor system integrated with a laser-induced graphene metal interdigitated array (LIG-MIDA) biosensor modified with carbon nanotubes and silver nanoparticles. The amplitude (4 mm) and speed (8 mm/s) of the sensor movement, as well as the electrode nanoparticle composition (2 % MWCNTs and 10 % AgNPs), were optimized to improve signal amplification and reproducibility. The proposed moving sensor was first demonstrated by measuring p-aminophenol (PAP), which exhibited higher signal stability, lower standard deviations, and a wide linear range (1 mM-10 pM) than the conventional static sensor. The proposed moving sensor achieved detection limits of 0.63 pg/mL for Aβ-40 and 0.78 pg/mL for Aβ-42 in buffer, approximately four times lower than that of the static sensors. Moreover, the proposed sensor was further verified by measuring the Aβ-42 biomarker in real plasma, which showed a similar sensitivity to buffer samples. Therefore, the developed system is clinically applicable for detecting Alzheimer's disease in its early stage.