13 March 2012 Immunoassay for CEA using the novel probe-labeled Ag nanoparticles based on surface-enhanced Raman scattering
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In this study, we report the Ag nanoparticles aggregated in the process of the labeling that use the crystal violet as the Raman probe. After this process- immune nanoparticles aggregate with high SERS sensitivity and biological specificity are created. We track and characterize the preparation by employing UV-Vi absorption spectra, Transmission Electron Microscope (TEM) and SERS spectra. With the increase of crystal violet, the aggregate of the Ag nanoparticles also increase, while the intensity of absorption peaks decrease. When the concentration of crystal violet reaches 1.0×10-4 mol/L, new peaks were found in the long wavelengths, and with the increase of the crystal violet, the intensity of the new peaks increase as well. We observe from the TEM, that with the increase of crystal violet, the aggregation degree of the Ag nanoparticles also increase and then they unite together. The SERS activity of the aggregates was directly related to the aggregation degree. Detecting the SERS activity of Ag NPs aggregates labeled with different amount of crystal violet, we found that with the increase of the crystal violet, the SERS signals of NPs aggregates enhanced. However, when the amount of crystal violet exceeded 25μL in 1mL colloidal silver, the Ag NPs occurred agglomeration and thereafter the next preparation of immune-label aggregates was hindered. Whereas, the probe labelled with 12μL crystal violet exhibited a better stability, stronger SERS activity and higher biological specificity, and it may accomplish a highly efficient SERS-based immunoassay. This immune probe was applied for detecting the expression of carcinoembryonic antigen (CEA) in the colon cancer tissue slice. Results show that appropriate immune aggregates labelled with optimum quantity of crystal violet present high stability, strong SERS activity and good immune specificity, which are expected to be applied in the analysis of the protein expression in the tissue section and promising for developing into a clinical tool for diagnosis.
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Xiaoqian Lin, Xiaoqian Lin, Gangqin Xi, Gangqin Xi, Yanping Chen, Yanping Chen, Gang Chen, Gang Chen, Xiongwei Zheng, Xiongwei Zheng, Jinping Lei, Jinping Lei, Lin Ou, Lin Ou, Shangyuan Feng, Shangyuan Feng, Haishan Zeng, Haishan Zeng, Rong Chen, Rong Chen, Liqing Sun, Liqing Sun, } "Immunoassay for CEA using the novel probe-labeled Ag nanoparticles based on surface-enhanced Raman scattering", Proc. SPIE 8329, Tenth International Conference on Photonics and Imaging in Biology and Medicine (PIBM 2011), 83290J (13 March 2012); doi: 10.1117/12.918954; https://doi.org/10.1117/12.918954

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