The magnetic beads-based sandwich-shaped immune complexes for rapid and sensitive amperometric detection of SOX2 protein.

Sex-Determining Region Y-box 2 (SOX2) is a transcription factor protein. SOX2 expression is related to lymph node metastasis and distant metastasis in colorectal carcinomas. SOX2 was determined with the first magnetic disposable immunoplatform. The designed sandwich-shaped immune complexes were formed by a capture antibody, SOX2 protein, and biotinylated secondary antibodies (dAb/HRP). The sandwich-shaped immune complex was linked to carboxylic acid functionalized magnetic beads (HOOC-MBs). This magnetic bioconjugate was dropped on the surface of the screen-printed carbon electrode (SPCE). The amperometric measurement was performed at -0.20 V in the presence of hydroquinone (HQ) and H₂O₂ against a silver pseudo-reference electrode. The optimization parameters affecting the immunoassay response were evaluated. The analytical evaluation of the magnetic disposable immunoplatform for the amperometric detection of SOX2 standards was done. The developed immunosensor shows high sensitivity (LOD of 1.37 ng mL^-1) and a short analysis time (15 min). Potential interfering compounds found in serum samples were tested. The storage stability of magnetic disposable immunoplatform was evaluated. The developed immunosensor was compared with the ELISA method.