Halloysite nanotubes-loaded conductive polymer as substrate and label material for sensitive detection of amyloid-β protein by electrochemical immunosensor

Amyloid-beta protein (Aβ) is a unique biomarker for Alzheimer's disease (AD). The sandwich-type electrochemical immunosensor, one of the key tools for detecting biomarkers, relies on a high-performance signal amplification approach to enhance its sensitivity. Ni/PdH nanodendrites (Ni/PdH NDs) have increased catalytic activity due to their unique interaction with palladium hydride and their nickel-rich surface, tunable shape and high specific surface area. Modified halloysite nanotubes (mHNT)-loaded with polypyrrole (PPy@mHNT) possess excellent dispersion and a large surface area. This enables the formation of a conductive network to prevent the accumulation of Ni/PdH NDs. Additionally, it exposes more electrocatalytic active centers, effectively amplifying electrical signals. By utilizing Ni/PdH@PPy@mHNT as the labeling material, it shows a consistent and remarkable electrocatalytic activity in H₂O₂ reduction, leading to signal amplification. The acid-etched HNT coated with polyaniline (PANI@eHNT) exhibits an exceptionally low background signal and outstanding conductivity. This not only accelerates electron transfer on the electrode surface, but also ensures the stable incubation of biomolecules post-amino grafting. Utilizing NH₂-PANI@eHNT as a substrate material can guarantee stable biomolecule incubation, offer a stable sensing platform and enhance immunosensor performance. The signal can be amplified and the immunosensor's sensitivity can be raised through the efficient cooperation of the aforementioned nanomaterials. Under optimum circumstances, the electrochemical immunosensor had the lowest detection limit of 5.53 fg mL^-1 and a linear range of 50 fg mL^-1 to 100 ng mL^-1. Based on the outstanding performance previously mentioned, this immunosensor is anticipated to aid in the early detection of AD.