Chiral Plasmonic Triangular Nanorings with SERS Activity for Ultrasensitive Detection of Amyloid Proteins in Alzheimer's Disease

Abstract

Chiral plasmonic nanomaterials have attracted unprecedented attention due to their broad applications in biomedicine, negative refractive index, and chiral sensing. Here, using a wet-chemistry process, chiral triangular Au nanorings are fabricated with a platinum (Pt) framework (l/d-Pt@Au triangular nanorings, named l/d-Pt@Au TNRs). The l/d-Pt@Au TNRs exhibit strong optical activity with a g-factor of 0.023 and can be used effectively for the discrimination of enantiomers due to selective resonance coupling between the induced electric and magnetic dipoles associated with enantiomers and the chiral plasmonic TNRs, also known as the surface-enhanced Raman scattering-chiral anisotropy (SERS-ChA) effect. The chiral d-Pt@Au TNRs represent a label-free SERS platform that can be applied to detect Aβ monomers and fibrils, the hallmarks of Alzheimer's disease (AD), achieving a limit of detection (LOD) down to 0.045 × 10^-12 m and 4 × 10^-15 m for 42-residue-long amyloid-β (Aβ₄₂ ) monomer and fibrils, respectively. Furthermore, chiral d-Pt@Au TNRs can also be successfully carried out to detect Aβ₄₂ proteins in AD patients with ultrahigh levels of sensitivity, thus allowing picogram quantities of Aβ₄₂ proteins to be identified. This research opens up an avenue for the use of chiral plasmonic nanomaterials as ultrasensitive SERS substrates to early diagnosis of protein-misfolding diseases.