Electrochemical immunosensor for detection of topoisomerase based on graphene–gold nanocomposites

A facile electrochemical immunosensor based on graphene–three dimensional nanostructure gold nanocomposites (G–3D Au) using simple and rapid one-step electrochemical co-reduction technique was developed for sensitive detection of topoisomerase. The resultant G–3D Au nanocomposites were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy, and then were used as a substrate for construction of the “sandwich-type” immunosensor. Amperometric current–time curve was employed to monitor the immunoreaction on the protein modified electrode. The proposed method could respond to topoisomerase with a linear calibration range from 0.5 ng mL−1 to 50 ng mL−1 with a detection limit of 10 pg mL−1. This new biosensor exhibited a fast amperometric response, high sensitivity and selectivity, and was successfully used in determining the topoisomerase which was added in human serum with a relative standard deviation (n=5)<5%. The immunosensor served as a significant step toward the practical application of the immunosensor in clinical diagnosis and prognosis monitor.