Grating Coupled Surface Plasmon Resonance Enhanced Fluorescence and Its Application for Cell Observation
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1208-O18-12
Grating Coupled Surface Plasmon Resonance Enhanced Fluorescence and Its Application for Cell Observation. Xiaoqiang Cui1, Keiko Tawa1 and Junji Nishii2 1 Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan. 2 Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan. ABSTRACT One-dimensional grating with 400 nm pitch was fabricated on a SiO2 glass surface. The grating was applied for detection of fluorescence excited by the electric field of the gratingcoupled surface plasmon resonance and highly sensitive observation of fluorescence image by optical microscope. 40-times of fluorescence enhancement was obtained under optimal condition after our systematically investigating depth and duty ratio dependent behavior. INTRODUCTION Fluorescence spectroscopy is rapidly becoming a leading methodology in life science and has been widely used in biological and medical research or diagnosis. Especially fluorescence microscopy is one of the most useful techniques in those fields. Improving its sensitivity, to get lower detection limit for analytical and biological science, remains a great challenge. The efforts to do this lead to a new area so called surface enhanced fluorescence (SEF)[1-3]. Up to now, most of the efforts for surface enhanced fluorescence were focused on metal nanoparticle based localized surface plasmon resonance, in which assembled nanoparticles or deposited nano islands were adopted[4-7]. However, nanoparticle method is greatly suffering from the poor reproducibility. On the other hand, the fluorescence enhancement based on propagated surface plasmon resonance (SPR) has been developed for reliable biospecific interaction analysis[5, 8, 9]. In this strategy, the Kretschmann geometry was used to get prism-coupled SPR by attenuated total internal reflection setup. In order to apply the fluorescence enhanced by SPR field for sensitively taking the fluorescence microscopic images, complicated optical setup such as prism and a large resonance angle around 60 degree at 630nm wavelength in water ambience are barrier in the view of utilizing a commercial microscope. Therefore, the fluorescence excited by the electric field of grating-coupled surface plasmon resonance (GC-SPR), which can be obtained at grating surface on the same side of the incident light, becomes an ideal candidate to upright fluorescence microscopic observation[10-12]. By adjusting the grating pitch, the coupling between surface plasmon polaritons (SPP) and radiation for excitation was obtained at a quite small incident angle, which will greatly benefit the observation of fluorescence under microscope without high numerical aperture (NA) objective lens. Recently, GC-SPR excited fluorescence was utilized for organic light-emitting diodes (OLEDs) and biosensor by Alq3 or dielectric grating structure composed of metal layer[13, 14], The application of GC-SPR excited fluorescen
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