Reduced graphene oxide field-effect transistor for label-free femtomolar protein detection

We report reduced graphene oxide field effect transistor (R-GO FET) biosensor for label-free ultrasensitive detection of a prostate cancer biomarker, prostate specific antigen/α1-antichymotrypsin (PSA-ACT) complex. The R-GO channel in the device was formed by reduction of graphene oxide nanosheets networked by a self-assembly process. Immunoreaction of PSA-ACT complexes with PSA monoclonal antibodies on the R-GO channel surface caused a linear response in the shift of the gate voltage, Vg,min, where the minimum conductivity occurs. The R-GO FET can detect protein-protein interactions down to femtomolar level with a dynamic range over 6-orders of magnitude in the Vg,min shift as a sensitivity parameter. High association constants of 3.2nM−1 and 4.2nM−1 were obtained for the pH 6.2 and pH 7.4 analyte solutions, respectively. The R-GO FET biosensor showed a high specificity to other cancer biomarker in the phosphate buffered saline solutions as well as in the human serum. ► R-GO FFET was applied to the ultrasensitive detection of cancer biomarkers. ► Residue-free R-GO channel in the FET enables femtomolar detection of proteins. ► The change of charge neutrality point shows a good linearity and large dynamic range.