Development of a P-tau217 Electrochemiluminescent Immunosensor Reinforced with Au–Cu Nanoparticles for Alzheimer’s Disease Precaution

To simply and rapidly detect the highly phosphorylated tau protein at threonine 217 (p-tau217) as a precautionary measure against Alzheimer's disease and distinguish it from other neurodegenerative diseases, a novel immunosensor was prepared using luminol as the electrochemiluminescent (ECL) sensing probe reinforced by Au–Cu nanoparticles (Au–Cu NPs). The Au–Cu alloy NPs were prepared via a co-reduction reaction, exhibiting excellent conductivity and catalytic activity. These properties remarkably enhanced the ECL of luminol, providing a suitable background for the sensing response. After the Au–Cu NPs were decorated on the surface of indium tin oxide glass using 3-amino-propyl trimethoxysilane, the antibody of p-tau217 was immobilized via dominant Au–N bonding to enable the biological specificity of the immunosensor. When p-tau217 specifically interacted with an antibody to form an immune complex on the sensing interface, the ECL signal of the sensor was considerably inhibited by the resulting giant biomolecular complex. This complex prevented luminol diffusion to the electrode surface and electron transfer. The resulting immunosensor showed remarkable sensitivity to p-tau217, with a wide linear detection range from 5 to 600 pg/mL. A detection limit of 0.56 pg/mL was achieved, with recoveries in human serum ranging from 92.3 to 109%. This ECL immunosensor demonstrated high sensitivity and specificity toward p-tau217, along with good reproducibility and stability, providing a new approach for clinical research on Alzheimer's disease.