Optical Waveguide Biosensors for Highly Sensitive and High-Throughput Applications
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Optical Waveguide Biosensors for Highly Sensitive and High-Throughput Applications Ikuo Uematsu1, 2, Ichiro Tohno2, Shingo Kasai2, Masaaki Hirakawa2, Kayoko Omiya2, and Hidetoshi Matsumoto1 1 Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Mail Box S827, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan 2 Corporate Manufacturing Engineering Center, Toshiba Corporation, 33 Shin-Isogo-Cho, Isogoku, Yokohama 235-0017, Japan ABSTRACT In the present study, highly sensitive and high-throughput optical waveguide biosensors were fabricated by using the sensing membranes containing dye and polymer-enzyme complex. Optical light waveguide can detect the optical change in the vicinity of the guide surface with high sensitivity due to the evanescent wave scattering. The glucose sensing membranes, composed of dye, enzymes, and biocompatible polymers were prepared by solution processing on the optical waveguide. Herein, we used 3, 3’, 5, 5’-tetramethylbenzidine (TMBZ) as a dye, glucose oxidase (GOD) and peroxidase (POD) as enzymes, phosphatide polymer for protection of biological activity of enzyme, and carboxymethyl cellulose (CMC) as a binder. Then we focused on the optimal composition and structure of sensing membranes for the enhancement in the sensitivity and response speed. The developed glucose sensors demonstrated 20 times higher sensitivity than the conventional light waveguide glucose sensors and the low-detection limit of 0.1g/L glucose within the detection time of 60 sec. For further improvement in the sensitivity, microporous sensing membranes were fabricated by using electrospraying technique. The electroprayed sensing membranes gave 40 % higher sensitivity than nonporous sensing membranes. These results show that both the composition and structure of sensing membrane are crucial factors for highly sensitive and high-throughput optical waveguide biosensors. INTRODUCTION In the field of clinical diagnostics, highly sensitive sensing system is strongly required to quickly obtain diagnostics results during medical treatments or to continuously monitor a very small amount of specimens of subcutaneous tissue fluid. Optical waveguide sensors have attracted much attention in the field of chemical and biological sensing applications, due to their high sensitivity, fast response rate, and compactness and convenience [1]. In particular, glucose (Glc) biosensors have continuous research interests for the accomplishment of more reliable in vitro or in vivo measurements. Figure 1 shows the schematic diagram of our optical waveguide sensor [2, 3]. A pair of diffraction gratings is fabricated by line-and-space patterning of titanium dioxide (TiO2) film in the vicinities of both ends of the glass substrate. Protective film with high-refractive-index (approximately 1.5 times higher than glass substrate) is coated on the gratings. The Glc sensing membrane is formed between the two gratings. The incident light from a laser emitting diode into one grating is diffracted in the waveguide and then emitted from
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