Multiplex paper-based electrochemical immunosensor for the simultaneous monitoring of blood biomarkers in Alzheimer's disease

Joint analysis of varied biomarkers in blood sample will provide more accurate results for the monitoring and management of Alzheimer's disease (AD). In addition to the known β-amyloid protein (Aβ) used as a reliable clinical marker for AD diagnosis, Fetuin B also demonstrates a strong correlation with AD progression. Especially, for medical diagnostics, on-site detection of multi-analyte is quite important and therefore, it is desirable to develop a rapid and portable, multiplex electrochemical assay for simultaneous detection of Aβ and Fetuin B, which has been seldomly reported before. To achieve this goal, a multiplex paper-based electrode was prepared via vacuum filtration, by which, single-walled carbon nanotubes (SWCNTs) and AuNPs were sequentially filtered through cellulose paper with a five-electrode pattern to form a conductive underlay and electrical connections. A nanocomposite of AuNPs-loaded dendritic mesoporous silica nanoparticles (dmSiO2-Au) was firstly synthesized and further deposited thionine (Thi) for signal amplification. An immunosensor was correspondingly fabricated, which involved a combination of multiplex electrodes and dmSiO2-Au-Thi nanocomposite to facilitate simultaneous monitoring of Aβo and Fetuin B. Additionally, ferrocene (Fc) was applied onto a separate working electrode to perform a ratiometric electrochemistry for enhancing accuracy. The outcomes demonstrated high specificity, sensitivity, and stability, and no obvious cross-talking between three working electrodes. Application of this sensor resulted in a successful determination of Aβo and Fetuin B levels in serum and brain tissue of transgenic AD mice. Overall, the presented electrochemical immunosensors for performing multiplex diagnostics may facilitate to the exploration of more AD-related blood markers.