Nonlinear optical detection of proteins based on localized surface plasmons in surface immobilized gold nanospheres.
A new nonlinear optical method is presented to detect proteins binding to a gold surface without using fluorescent-dye labeling. After exposure of the protein-binding surface to a gold nanosphere solution, the nanospheres are immobilized above a gold surface with a nanogap supported by the protein. The gold nanospheres immobilized on the gold surface show strong localized surface plasmon (LSP) resonance, and the formation of this structure results in a marked increase in the optical second harmonic (SH) activity of the gold surface arising from a large enhancement of the electric field localized adjacent to the nanospheres on the LSP resonance. The SH image, therefore, gives a high contrast ratio, 7.0:1, of protein-binding spots to control spots. The contrast ratio is much greater than those obtained by linear reflectivity imaging.
Fukuba
Shin-Ya
SY
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
Tsuboi
Kazuma
K
Abe
Shinya
S
Kajikawa
Kotaro
K
D002384:Catalysis; D004058:Diffusion; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D054118:Nanospheres / Q000737:chemistry* / Q000648:ultrastructure; D017711:Nonlinear Dynamics; D010777:Photochemistry; D011506:Proteins / Q000737:chemistry*; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D020349:Surface Plasmon Resonance; D013696:Temperature; D014961:X-Ray Diffraction
D011506:Proteins; D006046:Gold