Ultrasensitive detection of CEA in human serum using label-free electrochemical biosensor with magnetic self-assembly based on α-Fe2O3/ Fe3O4 nanorods

Early-stage colorectal cancer (CRC) is often asymptomatic, leading to late diagnoses and impacting treatment outcomes. Timely detection and diagnosis are crucial, with serum carcinoembryonic antigen (CEA) levels playing a key role in CRC diagnosis and prognosis. To enhance precision, a label-free electrochemical nano-biosensor utilizing magnetic self-assembly (MSA) technology was developed for sensitive CEA detection. The biosensor's core was the alpha-Fe2O3/Fe3O4 nanorods prepared by the hydrolysis-calcination reduction process. Its unique magnetism was the cornerstone of MSA technology. The biosensor exhibited excellent mechanical strength, ensuring stability during storage at 4 degrees C for at least one month. The aptamer probe (CEAA) self-assembled on the nanorods' surface via an Au-S bond, creating the magnetic probe (CEAA/alpha-Fe2O3/Fe3O4@Au). Upon capturing CEA, the current response decreased, indicating a "turn-off" nano-biosensor type as observed through differential pulse voltammetry (DPV) monitoring. In this research, the biosensor not only exhibited robust specificity and superior anti-interference ability but also demonstrated successful regeneration. The limit of detection (LOD) was 0.197 pg/mL, the recovery rate for real serum samples was between 94.15 % and 105.08 %, and the relative standard deviation (RSD) ranged from 1.40 % to 2.09 %. This biosensor showed promise in enhancing the accuracy and effectiveness of CRC diagnostic and prognostic protocols, offering a new direction for point-of-care testing.