Ultrasensitive SERS-Based Immunoassay of Tumor Marker in Serum Using Au–Ag Alloy Nanoparticles and Ag/AgBr Hybrid Nanostructure

Ultrasensitive detection of alpha-fetoprotein (AFP) is critical for the early diagnosis of liver cancer. In this work, a novel surface-enhanced Raman scattering (SERS)-based immunoassay complex has been successfully developed for the detection of AFP by using the Au-Ag alloy nanoparticals and the Ag/AgBr hybrid nanostructure. As the typical bimetal or metal/semiconductor plasmonic materials, besides the strong SERS enhancement characteristics, the Au-Ag alloy nanoparticals exhibit excellent monodispersity and the Ag/AgBr hybrid nanostructure demonstrates good stability. The experimental results show that the SERS-based immunoassay of AFP presents a low limit of detection of 1.86 fg/mL and a broad dynamic range from 2 fg/mL to 0.8 μ g/mL. Furthermore, the clinical applicability of the proposed SERS-based immunoassay has been assessed by the detection of AFP in the human serum samples of cancer patient and healthy person. The test data are consistent well with that of chemiluminescence immunoassay (CLIA) in the relative errors of − 8.82–8.06% and show better detection sensitivity. It reveals that the proposed immunoassay protocol is significant for giving insight into the design of ultrasensitive biosensor and the point-of-care testing of cancers.