Nanoplasmonic assay platforms for reproducible SERS detection of Alzheimer's disease biomarker

Abstract With the recent developments in high‐sensitivity optical detection technologies, many studies have been conducted to accurately detect biomarkers with low concentrations of 1.0 pM or less as well as apply them to in vitro diagnostics. The tubulin‐associated unit (tau‐381) protein, a biomarker of Alzheimer's disease, is one such representative example, and its cut‐off value reported in clinical practice is 5.5 fM. Therefore, a robust sensing technology that can stably detect such low concentrations of biomarkers is needed. In this study, tau‐381 was detected with high sensitivity and reproducibility by a plasmonic Au nanopopcorn substrate fabricated via thermal evaporation. Here, aptamer DNAs labeled with Raman reporters on the terminal were used as the receptors. The plasmonic nanopopcorn substrate used in this study is composed of uniform gold nanoparticles (AuNPs) of average size 64 nm. The reproducibility was significantly improved through more uniform nanogaps than those formed by aggregation of AuNPs in solution. An assay was conducted by first reacting tau‐381 with the corresponding aptamers, and the remaining aptamer DNAs were then reacted with capture DNAs immobilized on the surface of the Au substrate. The assay results for tau‐381 showed a limit of detection value of 2.2 fM, which is below the cut‐off value (5.5 fM).