Construction of a microcavity-based microfluidic chip with simultaneous SERS quantification of dual biomarkers for early diagnosis of Alzheimer's disease.

Since there is no effective Alzheimer's disease (AD)-modifying therapy available currently, early analysis of AD core biomarkers has become one of great significance and common concern in clinical diagnosis. Herein, we designed an Au-plasmonic shell attached polystyrene (PS) microsphere in a microfluidic chip for simultaneous detection of Aβ1-42 and p-Tau181 protein. The corresponding Raman reporters were identified in femto gram level by ultrasensitive surface enhanced Raman spectroscopy (SERS). Both of Raman experimental data and finite-difference time-domain modeling demonstrates the synergetic coupling between PS microcavity with the optical confinement property and the localized surface plasmon resonance (LSPR) of AuNPs, so leading to highly amplified electromagnetic fields at the 'hot spot'. Moreover, the microfluidic system is designed with multiplex testing and control channels in which the AD-related dual proteins were detected quantitatively with a lower limit of 100 fg mL. Thus, the proposed microcavity-based SERS strategy initiates a new way for accurately prediction of AD in human blood samples and provides the potential application for synchronous determination of multiple analytes in general disease assays.