Impedimetric aptasensing of the breast cancer biomarker HER2 using a glassy carbon electrode modified with gold nanoparticles in a composite consisting of electrochemically reduced graphene oxide and single-walled carbon nanotubes.

A method is presented for electrochemical determination of the breast cancer biomarker HER2. A glassy carbon electrode (GCE) was modified with densely packed gold nanoparticles placed on a composite consisting of electrochemically reduced graphene oxide and single walled carbon nanotubes (ErGO-SWCNTs). An aptamer directed against HER2 was then immobilized ono the GCE. The modified GCE was characterized by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The immobilized aptamer selectively recognizes HER2 on the electrode interface, and this leads to an increased charge transfer resistance (R_ct) of the electrode when using ferri/ferro-cyanide as the electrochemical probe. The method has a low limit of detection (50 fg·mL^-1) and a wide analytical range (0.1 pg·mL^-1 to 1 ng·mL^-1). The assay is highly reproducible and specific. Clinical application was demonstrated by analysis of the HER2 levels in serum samples, and sera of breast cancer patients were successfully discriminated from sera of healthy persons. Graphical abstract An electrochemical aptasensor for HER2 is described that is based on the immobilization of anti-HER2 aptamer on a glassy carbon electrode modified with a nanocomposite prepred fromreduced graphene oxide, carbon nanotubes and gold nanoparticles.