Plasmonic Cu2- xS ySe1- y Nanoparticles Catalyzed Click Chemistry Reaction for SERS Immunoassay of Cancer Biomarker.

Nature enzyme-based immunoassays have been widely used in fundamental scientific research and clinical diagnosis. However, the limitations of natural enzyme, such as the low physical/chemical stability or susceptibility to protein denaturation, greatly restrained its applications. In this article, we reported a new enzyme-free SERS immunoassay by utilizing plasmonic Cu2- xS ySe1- y nanoparticles (NPs) as nanocatalyst to catalyze the click chemistry between the azido and alkynyl substrate which is used as the SERS signal reporter. The unique vibration of C≡C of alkynyl in the Raman-silent region (1800-2800 cm-1) is not overlapped with the signals of the other conventional Raman reporters or endogenous biological species, and thus it can make sure the enzyme-free SERS immunoassay has high selectivity and sensitivity. As a proof of concept, prostate-specific antigen (PSA), a biomarker of prostate cancer in blood, has been detected. The SERS immunoassay shows good analytical performance for PSA in the range of 3-120 ng mL-1, and it has been successfully applied to detect PSA in the serum samples of prostate cancer patients, proving that the proposed enzyme-free SERS immunoassay has great potential in the clinical diagnosis of cancer.