Lipid Coated In-Situ Synthesize Gold Nanorods as Surface Enhanced Raman Scattering Substrate for Detection of Bacteriorhodopsin

• Main Authors: Li, Chen-Chi, 李振綺
• Other Authors: Yang, Tzyy-Schiuan
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/18577343348109244442

碩士 === 國立中正大學 === 化學暨生物化學研究所 === 101 === The optical properties of gold nanorods (AuNRs) can be varied by changing the aspect ratio (length/width). This feature can be simply identified by the UV-vis absorption spectrum. This is, when the aspect ratio changes, the plasmonic absorption bands of AuNRs shift. This phenomenon allows the wavelength of the absorption peak of gold nanorods to be adjusted to fit the excitation wavelength and the absorption peak of the analyte. The first part of this study is to use in-situ seed formation, instead of the pre-seed method, to simplify the AuNR sysntehsis and to examine the factors that influence the synthesis. The nucleation and growth reaction occur in the same pot. Therefore the preparation of a seed solution for the growth can be omitted. In the second part, we used phospholipids to replace hexadecyltrimethyl- ammonium bromide (CTAB) on the surface of AuNR for biomolecular detection. CTAB is toxic in biology and not suitable for applications in the biochemical field. In the third part, we used phospholipid-coated AuNRs to detect bacteriorhodopsin. The SERS spectrum of bacteriorhodopsin was analyzed and discussed. In the in-situ-seed-growth method, we first mixed CTAB solution (0.1 M) and tetrachloroauric acid solution (0.5 m M). Then, we added silver nitrate (0.02 mM), L-ascorbic acid solution (0.6 mM), and sodium borohydride (0.64 μM) solution in sequence. We use The reaction temperature was kept at 25℃and the reaction time was one hour. The UV spectrum showed that the gold nanorods synthesized by in-situ seed-growth method have greater aspect ratios than those prepared by the pre-seed-growth method in the same reaction concentrations.. The absorption of the longitudinal plasmonic band shifted to the near IR region. In order to fit to our laser excitation light (633 nm), we lowered the concentration of silver nitrate to adjust the absorption band of the long axis of AuNRs close to the laser wavelength. Next, we mixed CTAB- coated gold nanorods with phospholipid micelles to replace CTAB and produced phospholipid-coated gold nanorods. After lipid replacement, the absorption peak of AuNRs shifted to blue by 20 nm and the zeta- potential reduced to 25mV. These results proved the replacement of CTAB by phospholipids. The blue shift of the longitudinal Plasmon band implied the presence of a water layer between the phospholipid layer and the gold nanorod. Nile-red, a lipid probe, was used to test the sensing ability of phospholipid-coated AuNRs. The SERS spectrum of nile red on phospholipid coated AuNRs had fluorescence interference. Finally, we used phospholipid-coated gold nanorods to detect the orientation of bacteriorhodopsin in the charge-neutral lipid bilayer. By analyzing the SERS signals and examining the amino acid structure of bacteriorhodopsin, we suggest that bacteriorhodopsin inserted into phospholipid layer through the extracellular side.