Electrochemical immunosensors with AuPt-vertical graphene/glassy carbon electrode for alpha-fetoprotein detection based on label-free and sandwich-type strategies.

We proposed label-free and sandwich-type electrochemical immunosensors for the quantification of alpha-fetoprotein (AFP), which plays a critical role in the early diagnosis of primary liver cancer. Both detection strategies involved monitoring of the electrochemical response current of the AuPt-vertical graphene (VG)/glassy carbon electrode (GCE) for the oxidation of the redox probe, methyl orange. AuPt nanoparticles, which have good biocompatibility and excellent conductivity, were used to immobilize the primary antibody, Ab1, while VG sheets helped accelerate electron transfer at the liquid-solid and solid-solid interfaces. The sensing electrode played a key role in signal amplification, and the sensitivity of the sandwich-type sensor was higher than that of the label-free sensor. The former exhibited a wide linear range from 1 fg mL-1 to 100 ng mL-1 and a low detection limit of 0.7 fg mL-1 under the optimal experimental conditions. The excellent performance of the AuPt-VG/GCE-based immunosensors in AFP detection in human serum, coupled with their good stability, makes them promising tools for the clinical monitoring of AFP and other tumor markers.