An immunoassay detection based on surface-enhanced Raman scattering (SERS) from gold nanorods (NRs) was studied. Raman active molecule 4-mercaptobenzoic acid was adsorbed on gold NRs, forming SERS-tagged gold nanoprobes. Upon adsorption of antibody to the nanoprobes, the antibody was tagged by SERS. Through the immunoassay reactions among the SERS-tagged antibody, detected antigen, and antibody supported on solid substrate (capture antibody), SERS-tagged antibody-antigen-capture antibody sandwich conjugates were formed on the solid substrate. The higher the concentration of the detected antigen is, the larger the number of the gold nanoprobes on the solid substrate is. Therefore, SERS intensity signals the concentration of the detected antigen. Because the position of surface plasmon resonance (SPR) of the gold NRs can be tuned in a wide range, one can couple the SPR and the excitation line to maximize the SERS signals and thus the immunoassay sensitivity. The detected concentration for a single antigen component is higher than 1×10－8 mg•mL－1.

Key words: gold nanorod, thiolated PEG, 4-mercaptobenzoic acid, immunoassay, surface-enhanced Raman scattering