An innovative electrochemiluminescent immunosensor using dual amplified signals from AuNPs@CoSn(OH)6 for the detection of the AD biomarker: amyloid beta 1–40

Alzheimer's disease (AD) is a degenerative condition of the nervous system that causes severe damage to patients' daily activities and quality of life. Amyloid beta 1-40 protein (Aβ₄₀), which is involved in the formation of cerebral plaques, is one of the crucial biomarkers related to AD. Herein, a novel and highly sensitive immunosensor for the detection of Aβ₄₀ is developed. Using a reinforced indium tin oxide-coated glass with a nanocomposite of gold nanoparticle-enhanced CoSn(OH)₆ (AuNPs@CoSn(OH)₆) to trigger the electrochemiluminescence (ECL) of luminol as the sensing signal, the immunosensor is fabricated by immobilizing the Aβ₄₀ antibody onto it. By integrating the high immune specificity, excellent conductivity and catalytic activity of the nanocomposite, the resultant immunosensor can be successfully employed to detect the target in real samples. The formation of the immune complex leads to increased steric hindrance and electron transfer resistance, which in turn causes a declined ECL output when the target Aβ₄₀ binds to the antibody on the sensor surface. Under optimized conditions, the developed ECL immunosensor exhibits a linear response for Aβ₄₀ ranging from 1 to 800 pg mL^-1 and a low detection limit of 0.47 pg mL^-1. Experimentally, it is demonstrated to be highly sensitive, specific, reproducible and stable. This work extends the application of the perovskite CoSn(OH)₆ and AuNPs in the field of ECL immunosensing and provides a novel strategy for clinical research on Alzheimer's disease.