Amperometric Immunosensor Based on Carbon Nanotubes/Chitosan Film Modified Electrodes for Detection of Human Leptin

A novel sandwich electrochemical immunosensor was developed for the quantification of human leptin in serum using the glassy carbon electrodes modified with the single-walled carbon nanotubes/chitosan film. The preparation process of the biosensor involved covalently immobilization of a specific anti-human leptin antibody (capture antibody) on the modified glassy carbon electrodes, incubating with the target human leptin and reacting with the biotinylated anti-human leptin. After the well-known sandwich-type assembly, the streptavidin-alkaline phosphatase was attached to the immunosensor surface to catalyze the hydrolysis of the substrate alpha-naphthyl phosphate. The electrochemical impedance spectroscopy and square wave voltammetry were used to characterize biosensor. For detection of human leptin, the established immunosensor displayed a good amperometric response with a wide range of 0.05 ng mL(-1) - 500 ng mL(-1) and a detection limit of 30 pg mL(-1). Furthermore, good specificity and reproducibility were obtained, and this immunosensor was successfully applied to assay the leptin in spiked serum. The results demonstrated that the novel strategy might become a potential alternative for human leptin assay in the function study of human leptin and clinical diagnostic application.