Ultrasensitive flexible FET-type aptasensor for CA 125 cancer marker detection based on carboxylated multiwalled carbon nanotubes immobilized onto reduced graphene oxide film

The development of a novel flexible and ultrasensitive aptasensor based on carboxylated multiwalled carbon nanotubes (MWCNTs)/ reduced graphene oxide-based field effect transistor (FET) has been reported for label-free detection of the ovarian cancer antigen (CA125). The fabricated sensor has a straightforward design based on the noncovalent attachment of MWCNTs/aptamer conjugated onto few layers reduced graphene oxide nanosheets and its integration with poly-methyl methacrylate (PMMA) as a suitable platform for designing flexible field-effect transistors. The surface properties of the aptasensor were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Under optimal conditions, the proposed aptasensor exhibited a wide linear dynamic range for CA125 (1.0 × 10^-9-1.0 U/mL) with a low detection limit of 5.0 × 10^-10 U/mL. The proposed aptasensor was also successfully applied to detect CA125 in real human serum samples. Furthermore, sensor flexibility is also a challenging area in chemical and biological sensors, especially for portable, wearable, or even implantable sensors, so, the reduced graphene oxide-based FET-type aptasensor showed bendable flexibility on the PMMA substrate. In addition, the aptasensor exhibited high sensitivity, selectivity, stability and reproducibility which offers great promise as a high performance and flexible FET-type aptasensor to detect CA125 and other cancer biomarkers in clinical samples and biological fluids.