Carbon nanosphere-functionalized graphenenanosheets for sensing biomolecules based on platinum nanoflower labeling

Abstract

A specific sandwich-type electrochemical immunosensor for the sensitive detection of neuron-specific enolase (NSE) is described by using platinum nanoflower (PtNF)-labeled horseradish peroxidase-anti-NSE conjugate (HRP-mAb₂) as a secondary antibody on a carbon nanosphere-functionalized graphene sensing platform. In the presence of the target NSE, the sandwiched immunocomplex is formed on the functionalized graphene sensing interface between the labeled mAb₂ on the platinum nanoflowers and the immobilized primary antibody (pAb₁) on the electrode. Upon addition of hydrogen peroxide to the detection solution, the horseradish peroxidase can catalyze the reduction of the hydrogen peroxide with the aid of the immobilized thionine on the electrode in pH 5.5 acetic acid buffer. Under the optimal conditions, the cathodic current of the as-prepared immunosensor increases with the increasing NSE concentration, and exhibits a dynamic linear range from 0.01 to 120 ng mL⁻¹ with a detection limit of 5.0 pg mL⁻¹ NSE at S/N = 3. Intra- and inter-assay coefficients of variation were below 10%. The methodology was evaluated by assaying spiked serum samples, and the variation coefficients were 1.9–3.6%.