Electrochemical aptasensor for the detection of HER2 in human serum to assist in the diagnosis of early stage breast cancer

Human epidermal growth factor receptor-2 (HER2) is an important biomarker in the diagnosis and prognosis of breast cancer. This work aimed to develop an aptasensor to detect HER2 in human serum. HER2 aptamer was immobilized by electrostatic adsorption on the surface of a homemade screen-printed electrode modified with poly-l-lysine. Measurements were made by differential pulse voltammetry using methylene blue as a redox indicator. A calibration curve was constructed (R2 = 0.997) using different concentrations of HER2 protein (10–60 ng/mL) in PBS buffer (pH 7.4), with a detection limit of 3.0 ng/mL. The aptasensor showed good reproducibility with relative standard deviations (RSDs) of 3% and remained stable for 3 days with an RSD around 2%. When the tests were performed with serum from a healthy woman, a peak of 6.72 μA was found without the addition of the protein. When we tested the serum of a woman with HER2+ breast cancer, we obtained a signal of 2.65 μA; the same pattern was found when adding to protein in serum control, i.e., the higher the concentration of protein, the lower the signal. The aptasensor was characterized by scanning electron microscopy and isothermal titration calorimetry (ITC), showing excellent interaction between aptamer and target protein. The results revealed a promising and sensitive tool capable of detecting HER2 protein in human serum with albumin depletion, aiding in the molecular diagnosis of breast cancer.