Advanced electrochemical impedance immunosensor based on PS-b-PAA film architecture for sensitive alpha-fetoprotein detection

Alpha-Fetoprotein (AFP) is an important tumor biomarker closely associated with the early diagnosis of hepatocellular carcinoma and other diseases. To achieve rapid and highly sensitive AFP detection, this study developed a label-free electrochemical impedance immunosensor with enhanced sensitivity based on Polystyrene- block -poly acrylic acid (PS-b-PAA) thin films and a biotin-streptavidin (B-SA) amplification strategy. The sensor utilizes the unique properties of PS-b-PAA thin films, where carboxyl groups (-COOH) form covalent bonds with the amino groups (−NH 2 ) of streptavidin, combined with the B-SA system to achieve efficient antibody immobilization. The results showed that the B-SA system significantly enhanced antibody immobilization efficiency, reduced non-specific adsorption, and improved the sensitivity and specificity of electrochemical signals. As a signal amplification strategy, the biotin-streptavidin system increased the sensing signal by approximately 2.19-fold. The sensor exhibited a linear response range from 0.05 ng/mL to 300.00 ng/mL and a detection limit of 0.02 ng/mL. Moreover, the sensor's performance in real human serum samples was consistent with that of the enzyme-linked immunosorbent assay (ELISA), demonstrating excellent reproducibility and long-term stability. This study shows that the fabricated electrochemical impedance immunosensor, based on PS-b-PAA thin films and the B-SA system, exhibits excellent performance in AFP detection, providing a reliable, rapid, and efficient solution for early cancer biomarker detection.