Fig. 5.
Specificity and reproducibility of the SERS immunoassay. (A, B) The SERS spectra from the sandwich specificity immunoassay of SARS-CoV-2 spike protein, HIV-1 p24, EBV GP350, CEA, AFP and BSA and corresponding peak intensities at 1077 cm−1. The concentration of target antigen is 0.1 ng mL−1 while the other proteins are 1 μg mL−1. (C) Reproducibility of SERS spectra of sandwich immunoassay structure. (D) Relative standard deviation (RSD) of the peak intensity at 1077 cm−1 and 1586 cm−1, respectively. The spectra were collected from different points of sandwich immunoassay structure.