Chiral Bimetallic Pt@Au Octapods with Spiral Four‐Petal Flower‐Like Symmetric Configuration as Sensitive SERS Probes

Here, we synthesized chiral bimetallic Pt@Au octapods by using l/d-cysteine-threonine (CT) dipeptide as chiral ligands. These had a distinct spiral four-petal flower-like symmetric configuration with a twisted concave morphology on each facet. The twisted concave structure of the Pt@Au octapods facilitated intraparticle coupling, resulting in highly concentrated electric fields within the concave regions, thus creating "hot spots" that produced a potent surface-enhanced Raman scattering (SERS) effect. The l-Pt@Au octapods showed a nearly twofold stronger SERS response to Aβ40 and Aβ42 monomers and fibrils than the d-Pt@Au octapods. The different association constants arose from the unique chiral recognition capabilities of the CT ligands on the surfaces of the l-Pt@Au octapods, which allowed them to form specific hydrogen bonds with Aβ40 and Aβ42 monomers and fibrils, producing significant differences in their Raman spectra. The data from clinical cerebrospinal fluid (CSF) samples showed that the quantitative analysis of the Aβ42/Aβ40 ratio with Raman spectroscopy can be used as an effective biomarker for the early diagnosis of Alzheimer's disease (AD), with a cut-off value of 0.085. Our results pave the way for the use of chiral nanomaterials with strong optical activities in the development of clinical testing instruments with biomedical applications.