A new, sensitive, low-cost, disposable ITO based electrochemical immunosensor for detection of SOX2, a biomarker of cancer
Abstract
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.