Simultaneous and ultrasensitive detection of Alzheimer's disease blood biomarkers using magnetic SERS-encoded...

Alzheimer's disease (AD) is a progressive neurodegenerative disorder requiring early diagnosis for effective intervention. The combination of blood Aβ₄₂/Aβ₄₀ ratio and p-tau-181 is recognized as a promising core biomarker panel for AD diagnosis. However, conventional detection methods suffer from limitations including time-consuming procedures, lack of multiplexing capability, and insufficient sensitivity. Herein, we developed a magnetic surface-enhanced Raman scattering (SERS)-encoded tags-based lateral flow immunoassay (LFIA) for simultaneous detection of Aβ₄₂, Aβ₄₀, and p-tau-181 on a single test line. Magnetic Fe₃O₄@Au nanoparticles were synthesized and modified with three distinct Raman reporters (DTNB for Aβ₄₂, 4-MBA for Aβ₄₀, and 2-MPY for p-tau-181) and corresponding detection antibodies. Under optimal conditions, the assay achieved rapid detection (∼28 min) and high sensitivity, with limits of detection of 93.33 fg/mL for Aβ₄₂, 218.78 fg/mL for Aβ₄₀, and 56.23 fg/mL for p-tau-181. The method exhibited excellent specificity against interfering substances (BSA, human IgG) and closely related species (Aβ₃₈, p-tau-217), as well as good reproducibility (RSD <5%) and stability (≥4 weeks). In clinical plasma samples (n = 40), the combined score (p-tau-181/(Aβ₄₂/Aβ₄₀)) progressively increased with disease severity and correlated well with MMSE scores and MRI MTA grades, capturing both cognitive decline and hippocampal atrophy. This magnetic SERS-encoded LFIA platform offers a rapid, sensitive, user-friendly, and multiplex-capable approach for early AD diagnosis and progression monitoring, showing promise for future point-of-care applications.