Thyroglobulin detection by biosensor based on two independent Si NW FETs

In this work we present a label-free, highly sensitive biosensors based on a silicon nanowire field effect transistor (Si NW FET) for the detection of the cancer biomarker - thyroglobulin. The Si structures with 70-90 nm width and 3-5 μm long NW were fabricated on silicon-on-insulator (SOI) substrates using e-beam lithography with a negative-tone resist and reactive-ion etching in a fluorine plasma. The metallic contact leads were carefully insulated by a sputtered silicon oxide layer to avoid a current leakage into analyte. The biomarker detection is based on a highly specific recognition of analytes by antibodies immobilized on the sensor surface. We used an original technique of antibodies covalent immobilization on small-sized gold nanoparticles (GNP) attached to the Si NW surface. The device was applied for the detection of ultra-low concentrations of thyroglobulin (Tg) in fetal bovine serum (FBS). Even the negligible change detection of the Tg level in the blood serum provides an early relapse and metastasis diagnostics of the differentiated thyroid cancer and evaluating the affectivity of the therapy. The limit of detection was estimated to be of ~6 pg/ml. Compared with the well-established commercial and experimental methods this is more sensitive.