An electrochemical aptasensor based on gold nanoparticles-modified graphene oxide for the ultrasensitive detection of breast cancer biomarker

Human epidermal growth factor receptor 2 (HER2), is encoded by a proto-oncogene located at the long arm of human chromosome 17q, plays an important role in human malignancies and is over-expressed in a high number of human breast cancers [1, 2]. The presence of HER2 on cancer cells is linked to increased cancer metastasis and tumour proliferation [3]. The aim of the present work is the fabrication of an electrochemical aptamer-based biosensor (aptasensor) for early diagnosis of breast cancer by detection of HER2. The proposed aptasensor was fabricated via covalent coupling of thiol-functionalized HER2-specific aptamer on the gold nanoparticles-graphene oxide film-modified glassy carbon (GC/rGO-AuNP) electrode. The resultant nanocomposite can provide a large surface area, excellent electrocatalytic activity, and high stability, which would improve immobilization sites for biological molecules, allow remarkable amplification of the electrochemical signal and contribute to improved sensitivity. HER2-specific aptamers were simply immobilized onto the rGO/AuNPs nanocomposite matrix. The electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to analyze the surface characterization of unmodified GCE and rGO/AuNPs modified GCE, and also the interaction between aptamer and HER2. In the presence of HER2, the aptamer on the adsorbent layer captures the target on the electrode interface, which makes a barrier for electrons and inhibits electron transfer, thereby resulting in decreased DPV signals of the modified GCE. Furthermore, the proposed aptasensor has a very low LOD of 0.05 ng mL-1 HER2 within the detection range of 0.02–50 ng mL-1. The aptasensor also presents high specificity and reproducibility for HER2, which is unaffected by the coexistence of other proteins.