A sensitive and disposable electrochemical immunosensor for detection of SOX2, a biomarker of cancer

A novel, sensitive, disposable indium tin oxide (ITO)-based electrochemical immunosensor was developed firstly for simple, rapid determination of Sex-determining region Y-box 2 (SOX2). SOX2 is a cancer biomarker and used for detecting small cell lung cancer, lung adenocarcinoma, squamous cell carcinoma, skin cancer, prostate cancer, and breast cancer. In this study, a disposable ITO thin film based electrode was used as working electrode for biosensing the interaction between SOX2 antigen and anti-SOX2 antibody. In this study, carboxyethylsilanetriol (CTES) was also utilized for electrode modifying so as to obtain self-assembled monolayers. The formed self-assembled monolayers were activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) chemistry and they were used as a heterobifunctional crosslinker and activator, respectively. Anti-SOX2 antibody was used as a biorecognition molecule and was covalently immobilized onto the ITO thin film modified with CTES. Immobilization steps were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optimum immobilization conditions such as antibody concentration, antibody and antigen incubation times were examined for the best sensitivity of the immunosensor. Under optimal conditions, this immunosensor had a wide linear detection range (25 fg/mL-2 pg/mL) with a detection limit as low as 7 fg/mL SOX2. Furthermore, the developed SOX2 immunosensor had good storage stability (79.36% of initial activity after 9 weeks), repeatability (3.88% of RSD) and reproducibility (4.25% of RSD). Our developed immunosensor has an acceptable performance for detection of SOX2 antigen, exhibits low detection limit, and has selective and reproducible results in immunoreaction analysis.