Electrodeposition of gold–platinum alloy nanoparticles on carbon nanotubes as electrochemical sensing interface for sensitive detection of tumor marker

A novel electrochemical sensing interface, electrodeposition of gold–platinum alloy nanoparticles (Au–PtNPs) on carbon nanotubes, was proposed and used to fabricate a label-free amperometric immunosensor. On the one hand, the multiwalled carbon nanotubes (MWCNTs) could increase active area of the electrode and enhance the electron transfer ability between the electrode and redox probe; on the other hand, the Au–PtNPs not only could be used to assemble biomolecules with bioactivity kept well, but also could further facilitate the shuttle of electrons. In the meanwhile, horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) was employed to block the possible remaining active sites and avoid the nonspecific adsorption. With the synergetic catalysis effect of Au–PtNPs and HRP towards the reduction of hydrogen peroxide (H2O2), the signal could be amplified and the sensitivity could be enhanced. Using alpha-fetoprotein (AFP) as model analyte, the fabricated immunosensor exhibited two wide linear ranges in the concentration ranges of 0.5–20ngmL−1 and 20–200ngmL−1 with a detection limit of 0.17ngmL−1 at a signal-to-noise of 3. Moreover, the immunosensor exhibited good selectivity, stability and reproducibility. The developed protocol could be easily extended to other protein detection and provided a promising potential in clinical diagnosis application.