A SERS-based immunoassay with highly increased sensitivity using gold/silver core-shell nanorods.

An immunoassay based on surface enhanced Raman scattering (SERS) has been developed using immuno-gold/silver core-shell nanorods with a high sensitivity. The features of these nanoparticles were characterized by UV-vis extinction spectra, TEM images, EDX analyses and SERS spectra. It was found that the obtained gold/silver core-shell nanorods showed a much higher SERS activity than uncoated gold nanorods. After the gold/silver core-shell nanorods were modified with antibody and employed in immunoassay, the antigen concentration-dependent SERS spectra and dose-response calibration curves were obtained. By comparison, it can be concluded that the detection limit of gold/silver core-shell nanorods based immunoassay reaches 70 fM, which is 10(4) times lower than gold nanorods based detection. As a result, SERS probes fabricated with gold/silver core-shell nanorods are demonstrated to be advantageous to those synthesized with gold nanorods due to their highly increased sensitivity in sandwich immunoassay, which also indicates the potential use of these gold/silver core-shell nanorods in other biological sensing applications.