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.
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
Shin-Ya
SY
Fukuba
Kazuma
K
Tsuboi
Shinya
S
Abe
Kotaro
K
Kajikawa
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