Gold Nanorods and Gold Nanospheres as Surface-Enhanced Raman Scattering Substrates for Biodetection

• Main Authors: Huang, Chia-Chi, 黃家琪
• Other Authors: Yang, Tzyy-Schiuan
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/18918112525450189207

博士 === 國立中正大學 === 化學暨生物化學研究所 === 101 === There are two biosensing approaches based on surface enhanced Raman spectroscopy (SERS): surface enhanced Raman tags (SERS tags) and label-free methods. In this study, the biosensor fabrication methodology and the signal amplification technique can be described as the following three parts: First, the status of protective layer of cetyltrimethylammonium bromide (CTAB) on gold nanorod (AuNR) surface can be modulated by controlling the concentration of CTAB. Thus, the monodispersive SERS core-shell tag based on an AuNR was fabricated successfully. Because of the core-shell structure, the SERS tags were more stable and the outer shell can provide a larger surface area for biomoleculear immobilization. AuNR SERS core-shell tags attached to polystyrene bead which mimics bacteria via biotin–streptavidin labeling protocol were used in SERS detection. These results show that the SERS signal intensity of AuNR core-shell SERS tags is about 1/3 fold compared to that of the nanoaggregate-embedded beads (NAEBs), suggesting a strong enhancement effect from the AuNR substrate. Moreover, the SERS signal variation among six repeated measurements of the detected AuNR core-shell beads was within 6%. Besides, the AuNR core-shell SERS tag encoded with both fluorescence characteristic and Raman signatures may lead to a kind of powerful dual-mode biosensor. Second, 5 different types of SERS substrates were fabricated and applied to detection of 20 kinds of amino acids, mimicked RGD (Arg-Gly-Asp) peptides and snake venom. The SERS efficiency of 5 different SERS substrates was compared. Among these SERS substrates, the dog-bone shaped gold nanorod exhibited excellent SERS enhancement. Furthermore, this substrate can successfully distinguish the secondary protein structure between Bungarus multicinctus and Trimeresurus stejnegeri from their collected SERS spectra. According to the SERS results of dog-bone shaped AuNRs, the present work has developed a SERS substrate suitable for biological macromolecules detection. Third, the model of the effect of CTAB morphology on the surface properties of AuNR accompanied by varying the solution CTAB concentration was established, and this model applied to DNA sequence detection was further demonstrated. The SERS signal of Hum23 at 2 × 10-7 M resulting from the coulombic interactions between the positive charge of CTAB and negative charge of Hum23 sequence (TAGGG(TTAGGG)3) was detected successfully. Furthermore, the anticancer drug 3,6-bis(1-methyl-4-vinylpyrazinium)carbazole diiodide (BMVC-4) and Hum23 sequence can form a complex and directly absorb on AuNR surface. According to the difference SERS spectra of BMVC-4 after interacting with Hum23, the results indicate that the pyrazine ring interacts with the backbone of DNA. Thus, this model could be a protocol for controlling the analyte absorbed on the Au surface, indicating the potential of AuNRs as a substrate for SERS detection.