Ultrasensitive electrochemical immunosensor for ProGRP detection based on 3D-rGO@Au nanocomposite

In this work, an ultrasensitive and low-cost electrochemical immunosensor has been constructed for ProGRP detection. The prepared three-dimensional reduced graphene oxide-gold nanoparticles (3D-rGO@Au) composite as substrate materials were applied for electrode modification, which can enhance electrical conductivity and enlarge the effective surface area for immobilizing capture antibody. Detection antibody-coated non-conductive SiO 2 nanospheres were used for specifically recognize ProGRP and form a sandwich structure. The electrochemical response signal of the sandwich-type immunosensor was based on the electron transferability between the electrode and [Fe(CN) 6 ] 3−/4− . 3D-rGO@Au can significantly increase the initial current, while SiO 2 can greatly reduce the response current. The combined effects of these nanomaterials can thus effectively enhance the sensitivity. Under optimal conditions, the constructed immunosensor exhibited a wide linear range (1 fg/mL to 10 ng/mL) with a low limit of detection (0.14 fg/mL). Moreover, the immunosensor exhibited superior stability, good reproducibility, favorable selectivity, and high sensitivity. Meanwhile, the concentration of ProGRP in human serum samples was measured with satisfactory results. This device is promising in the early screening of lung cancer, which can be applied as an over-the-counter test at home or in the community.