Sensitive colorimetric immunosensor using AuNP-functionalized polymer film for picogram-level detection of Tau protein intermediate aggregates.

Here we demonstrate for the first time that an antibody-gold nanoparticles (AuNPs)-polymer conjugate thin-film biosensor can easily be fabricated to selectively capture Tau protein. Gold nanoparticles (AuNPs) are employed as sensing elements, thus capitalizing on their propensity to undergo assembly or disassembly in response to the adsorption or conjugation of various biomolecules on their surface, thereby forming robust interactions with the target analyte. We show that the Tau protein in its different aggregation phases can be detected, by restricting the reaction area on the solid thin polymer film and thus reducing the diffusion effects usually encountered in immunosensors. A limit of detection (LOD) of 460 pg/mL was reached, demonstrating a great potential for detecting Tau in aggregation states. This sensor based on thin polymer film could open new routes for sensing and monitoring Tau protein in biological assays and biomedical diagnosis.