Keiko Tawa

Major research fields

KeikoTawaSurface plasmon, Fluorescence imaging, Biosensor

   A “plasmonic chip” is the substrate including a wavelength-scale grating covered with thin metal layers. It can provide the enhanced fluorescence excited by the electric field based on the surface plasmon resonance. Therefore, a “plasmonic chip” has been developed for application to fluorescence bioimaging and immunosensors. Only using a plasmonic chip instead of a glass slide on a sample stage of fluorescence microscope or immunosensors can improve the detection sensitivity without further improvement of optical setup and stuffs,.

   Up to now, in the immunosensors platform on the plasmonic chip, 300x fluorescence enhancement was achieved compared with that on the glass slide. The limit of detection of antigen marker was at least several tens of fM (~ pg/mL). Such a high detection sensitivity was considered to be valid for a clinical diagnosis such as the blood test at an early stage. In fluorescence imaging, 10x brighter image was observed for neuronal cells of rat cultured on the plasmonic chip than that on the conventional glass-bottomed dish. In multicolor fluorescence imaging of cancer cells, brighter images were also obtained.

   We hope to collaborate for application of the plasmonic chip not only to biology, but also to environmental chemistry, energy science, and various fields.

Major relevant publications

  1. K. Tawa*, F.. Kodo, C. Sasakawa, K. Nagae, Y. Nakamura, A. Nozaki, T. Kaya, “Sensitive Detection of a Tumor Marker, α Fetoprotein, with a Sandwich Assay on a Plasmonic Chip,” Analytical Chemistry, 87(7), 3871–3876 (2015).
  2. K. Tawa*, C. Yasui, C. Hosokawa, H. Aota and J. Nishii, ”In Situ Sensitive Fluorescence Imaging of Neurons Cultured on a Plasmonic Dish Using Fluorescence Microscopy”, ACS Appl. Mater. Interfaces, 6 (22), 20010–20015 (2014).
  3. K. Tawa*,M. Umetsu, H. Nakazawa, T. Hattori, and I. Kumagai “Application of 300× Enhanced Fluorescence on a Plasmonic Chip Modified with a Bispecific Antibody to a Sensitive Immunosensor”, ACS Appl. Mater. Interfaces, 5 (17), 8628–8632 (2013).
  4. XQ. Cui, K. Tawa*, H. Hori, and J. Nishii “Tailored Plasmonic Gratings for Enhanced Fluorescence Detection and Microscopic Imaging” Adv. Funct. Mater. 20, 546-553 (2010).
  5. K. Tawa and W. Knoll*, “Mismatching base-pair dependence of the kinetics of DNA-DNA hybridization studied by surface plasmon fluorescence spectroscopy”, Nucleic Acids Research, 32, 2372-2377 (2004).