Construction and evaluation of AuNPs enhanced electrochemical immunosensors with [Fe(CN)6]3-/4- and PPy probe for highly sensitive detection of human chorionic gonadotropin.

Human chorionic gonadotropin (HCG), a vital protein for pregnancy determination and a marker for trophoblastic diseases, finds application in monitoring early pregnancy and ectopic pregnancy. This study presents an innovative approach employing electrochemical immunosensors for enhanced HCG detection, utilizing Anti-HCG antibodies and gold nanoparticles (AuNPs) in the sensor platform. Two sensor configurations were optimized: BSA/Anti-HCG/c-AuNPs/MEL/e-AuNPs/SPCE with [Fe(CN)6]3-/4- as a redox probe (1) and BSA/Anti-HCG/PPy/e-AuNPs/SPCE using polypyrrole (PPy) as a redox probe (2). The first sensor offers linear correlation in the 0.10-500.00 pg∙mL-1 HCG range, with a limit of detection (LOD) of 0.06 pg∙mL-1, sensitivity of 32.25 μA∙pg-1∙mL∙cm-2, RSD <2.47 %, and a recovery rate of 101.03-104.81 %. The second sensor widens the HCG detection range (40.00 fg∙mL-1-5.00 pg∙mL-1) with a LOD of 16.53 fg∙mL-1, ensuring precision (RSD <1.04 %) and a recovery range of 94.61-106.07 % in serum samples. These electrochemical immunosensors have transformative potential in biomarker detection, offering enhanced sensitivity, selectivity, and stability for advanced healthcare diagnostics.