SERS-based multiplex immunoassay of tumor markers using double SiO2@Ag immune probes and gold-film hemisphere array immune substrate

Highly sensitive and specific detection of tumor markers is extremely significant for the early diagnosis and treatment of cancer. We proposed a novel surface-enhanced Raman scattering (SERS)-based multiplex immunoassay proposal to implement the ultrasensitive detection of multiple tumor markers. In our work, the prostate specific antigen (PSA) and a-fetoprotein (AFP) as two kinds of target analytes were simultaneously detected by using the sandwich immune complex consisted of 4MBA-labeled SiO2@Ag immune probes, 4NTP-labeled SiO2@Ag immune probes and the gold-film hemisphere array (Au-FHA) immune substrate. And the selection of Raman molecules and the regulation of SERS signals among the probes are the technical keys to realize the effective multiplex immunoassay. The experiment results demonstrate that the constructed immunoassay platform exhibits a wider dynamic linear range from 10 fg mL(-1) to 400 ng mL(-1) and the limit of detection of 3.38 and 4.87 fg mL(-1) for PSA and AFP, respectively. And more, the CA-125 was selected as an unspecific antigen to verify the high-specificity of the multiplex immunoassay. In addition, the PSA and AFP in human serum samples had been detected by the proposed immunoassay proposal and the test data present a good consistent with that of chemiluminescent immunoassay (CLIA). It is expected that the SERS-based multiplex immunoassay proposal could be applied in the practical clinical diagnoses of cancer.