Capillary-integrated chiral gold nanocrystals for label-free SERS detection of serum amyloid-β 1-42 in Alzheimer's disease rats.

Chiral plasmonics was integrated with surface-enhanced Raman scattering (SERS) technology to develop a high-performance chiral SERS sensor with promising applications for the early identification and ultrasensitive detection of Alzheimer's disease. The sensor utilizes the self-assembly of chiral gold nanocrystals (CG NCs) on the inner wall of a capillary, introducing a surface-enhanced Raman scattering chiral anisotropy (SERS-ChA) effect. Consequently, a label-free chiral SERS sensor ‌is‌ constructed. In the presence of the target analyte Amyloid-β 1-42 (Aβ1-42, Aβ42), CG NCs generate an electric-dipole-magnetic-dipole coupling effect within the chiral plasmonic field, resulting from selective resonance coupling between enantiomer-induced electric and magnetic dipole (MD) moments. This process significantly enhances the chiral asymmetric response and amplifies the SERS signal, allowing highly sensitive recognition and detection of Aβ42. The sensor exhibits excellent analytical performance, achieving a limit of detection (LOD) as low as 0.0899 pg/mL. Furthermore, it demonstrates strong selectivity for Aβ42 and robust resistance to interference from other substances commonly present in serum. By analyzing serum samples from rat models of Alzheimer's disease and comparing the results with those from an Aβ1-42 ELISA kit, a high correlation (R2 = 0.976) was demonstrated, validating the sensor's practicality and accuracy and indicating its stable and reliable quantitative performance in complex biological matrices. This study provides new insights and theoretical foundations for the early screening and diagnosis of Alzheimer's disease.