@article{Pham2020, 
author = {Xuan-Hung Pham and Eunil Hahm and Tae Han Kim and Hyung-Mo Kim and Sang Hun Lee and Sang Chul Lee and Homan Kang and Ho-Young Lee and Dae Hong Jeong and Hak Soo Choi and Bong-Hyun Jun},
title = {Enzyme-amplified SERS immunoassay with Ag-Au bimetallic SERS hot spots},
year = {2020},
journal = {Nano Research},
volume = {13},
number = {12},
pages = {3338-3346},
keywords = {surface-enhanced Raman scattering, surface-enhanced Raman scattering (SERS)-based immunoassay, Au-Ag alloy, silica template, immunoglobulin G (IgG) detection},
url = {https://www.sciopen.com/article/10.1007/s12274-020-3014-3},
doi = {10.1007/s12274-020-3014-3},
abstract = {Surface-enhanced Raman scattering (SERS) enables rapid detection of single molecules with high specificity. However, quantitative and sensitive SERS analysis has been a challenge due to the lack of reliable SERS-active materials. In this study, we developed a quantitative SERS-based immunoassay using enzyme-guided Ag growth on Raman labeling compound (RLC)-immobilized gold nanoparticle (Au NP)-assembled silica NPs (SiO2@Au-RLC@Ag). The enzyme amplified Ag+ reduction as well as Ag growth on the RLC-immobilized Au NP-assembled silica NPs (SiO2@Au-RLC), which resulted in a significant increase in SERS signal. In the presence of target antigens such as immunoglobulinG (IgG) or prostate-specific antigen (PSA), Ab1-Antigen-Ab2 immune complex with alkaline phosphatase triggered an enzyme-catalyzed reaction to convert 2-phospho-L-ascorbic acid (2-phospho-L-AA) to ascorbic acid (AA). As produced AA reduced Ag+ to Ag, forming an Ag hot spot on the surface of SiO2@Au-RLC, which enhanced the SERS signal of SiO2@Au-RLC@Ag in a solution with a target antigen concentration. The plasmonic immunoassay for IgG detection showed a high linearity of SERS intensity in the range of 0.6 to 9.0 ng/mL with a detection limit (LOD) of 0.09 ng/mL, while an LOD of 0.006 ng/mL was obtained for PSA. The results indicate that the sensitivity of our novel SERS-based immunoassay is higher than that of conventional enzyme-based colorimetric immunoassays.}
}