Shigeru Toyama

Design and fabrication of a waveguide-coupled prism device for surface plasmon resonance sensor

Abstract A novel waveguide-coupled prism device as a surface plasmon resonance sensor has been developed. The waveguide was fabricated by depositing Ag, SiO 2 , and Au thin films in this order on a prism. The device demonstrated a sharp absorption in the light reflectance curve due not only to the insertion of polarized light where electric field was parallel to the reflection plane (P-wave) but to that perpendicular to the reflection plane (S-wave). The experimental reflectance curves for both P- and S-waves were well predicted by the Fresnel formulas. The former and the latter absorptions are due to surface plasmon resonance and the attenuation of propagating light through the waveguide by the repetitive absorption at the metal/SiO 2 boundary, respectively.

Surface design of SPR-based immunosensor for the effective binding of antigen or antibody in the evanescent field using mixed polymer matrix

Abstract Hydroxyethyl starch (HES) and dextran sulfate (DS), having respective molecular weight of 258 000 and 12 100 thousand Dalton, were oxidized and then immobilized at the surface of a gold thin layer for a surface plasmon resonance (SPR) sensor. Human serum albumin (HSA) was immobilized at the activated polymer matrix and then the sensor worked as a sensing device for anti-human serum albumin (anti-HSA). The sensor exhibited the maximum response when the mixing ratio of HES to DS was 3:2 (w:w). The detection limit was down to 10−7 g ml−1 at this mixing ratio.

Surface plasmon resonance of electrochemically deposited Au-black

Au-black, a kind of gold nanostructure, was electrochemically deposited on a Au-vapor-deposited glass plate, and its optical properties were evaluated with a surface plasmon resonance (SPR) measurement system. The Au-black was found to exhibit an extraordinary high resonance angle (minimum reflectance angle) compared to that of the Au-vapor-deposited glass plate. We proposed a five-layer model, which consists of glass, Cr, Au, Au-black, and solution layers, to explain the high resonance angle of the Au-black plate. The calculation was based on the Fresnel formulas extended for multilayers. When the Bruggeman formula was used to obtain a refractive index of the Au-black layer, the numerical simulation could qualitatively explain the experimental observations. The curve fitting method by the five-layer model enabled us to simultaneously estimate the thickness of the Au-black layer and the volume fraction of Au in Au-black.

Measurement of voltage dependence of capacitance of planar bilayer lipid membrane with a patch clamp amplifier

The voltage dependence of capacitance was measured by using the setup which was almost the same as that for the study of ion channels. The coefficient which represents the voltage dependence of capacitance itself also changes as a function of the duration of voltage application if hexadecane is contained in bilayer lipid membrane (BLM). The method of Alvarez, O., and R. Latorre (1978. Biophys. J. 21:1-17) was extended to treat BLM with hexadecane.

Conformational change of photochromic spirobenzopyran in a bilayer lipid membrane observed via the current of ion-carriers

Abstract A change in the current of ion-carriers through a bilayer lipid membrane which contained a photochromic compound, was observed on irradiation with UV and visible light. The patterns of the current photoresponse depended on the type of ion-carrier.

Measurement of voltage dependence of capacitance of bilayer lipid membrane under the existence of ion carriers

The capacitance of a bilayer lipid membrane depends on the applied voltage. The difference of the boundary potentials of the two surfaces of the membrane can be obtained by using this property. However the conventional method have not taken the existence of ion-carrier in membrane into consideration. The current of ion-carrier changes nonlinearly by the applied voltage on the membrane, which cause difficulty to measure the voltage dependence of the capacitance. Here a method to avoid such a difficulty is described The validity of the method was checked both by experimentally and by the computer simulation.