A novel and highly sensitive sandwich-type immunosensor for prostate-specific antigen detection based on MWCNTs-Fe3O4 nanocomposite

Due to the importance of early diagnosis of prostate cancer, an ultrasensitive electrochemical immunosensor was developed to detect prostate-specific antigen (PSA) biomarker. The biosensor was designed based on modification of the glassy carbon electrode (GCE) surface with a nanocomposite of carboxyl functionalized multi-walled carbon nanotubes (MWCNTs), and Fe3O4 nanoparticles with unique properties for signal amplification that was synthesized using a new method. MWCNTs with COOH groups were a good substrate to modify the electrode for the binding of anti-total PSA antibody (Ab1) to form a sandwich-like structure. Also, Fe3O4 nanoparticles with their magnetic properties played a key role in signal amplification and facilitating electron transfer. Horseradish peroxidase (HRP)-labeled anti-free PSA antibody (Ab2) led to the reduction of hydrogen peroxide (H2O2) in the electrochemical cell and increased the current by adding a higher concentration of PSA that is the basis of the biosensor analysis performance. The immunosensor showed a limit of detection (LOD) of 0.39 pg/mL to measure PSA with a wide linear range from 2.5 pg/mL to 100 ng/mL. This immunosensor has high reproducibility and stability and indicated suitable performance for measuring PSA both in real serum samples and in laboratory solution. This raises hopes for the use of this type of sensor in diagnostic clinics in the future.