Since evaluating CA 19-9 antigen level in human serum is crucial for the early diagnosis of a vast range of diseases, especially pancreatic cancer, applying a simple, rapid, and sensitive detection method is essential. We employed an electrolyte-gated field-effect transistor with MoS 2 nanosheets channel as an immunosensor to recognize CA 19-9 tumor marker. In order to obtain MoS 2 nanosheets and use them as a semiconducting channel, the liquid phase exfoliation method was performed. Later, the MoS 2 channel surface was modified by covalent immobilization of antibody 19-9. Electrical measurements revealed the depletion mode n-type behavior of MoS2 nanosheets with the FET mobility of 0.02 cm2 V-1 s-1, current on/off ratio of 883.96, and the subthreshold swing of 795.54 mV/decade. Due to the n-type behavior of the MoS2-based FET immunosensor, with increasing the concentration of the CA 19-9 antigen at a wide linear concentration range from 1.0×10-12 U/ml to 1.0×10-4 U/ml, the source-drain current decreased and low detection limit of 2.8×10-13 U/ml was obtained. The designed MoS2-based FET immunosensor, owning high selectivity, performed accurately for trace amounts of real human serum samples. The remarkable properties of this immunosensor enable the diagnosis of pancreatic cancer in the early stages, which increases the chance of curing this disease.
