title: Optical waveguide sensor based on silica nanotube arrays for label-free biosensing.
abstract: Label-free biosensing based on optical waveguide spectroscopy of silica nanotube (SNT) arrays is realized with high sensitivity. The SNT arrays fabricated using a porous anodic alumina (PAA) template assisted by surface sol-gel (SSG) method showed a high value of 552 reciprocal refractive index unit as the sensing figure of merit by exchanging the sensing environment with water and ethanol. A standard biotin-streptavidin affinity model was tested using the SNT arrays which support a TM1 mode and the fundamental response of the system was investigated. Results show that the response of the SNT arrays for adsorption of streptavidin is higher than the one using substrate without removing the PAA template due to the larger surface area and the stronger electromagnetic field. The limit of detection (LOD) of the SNT arrays for detection of streptavidin was estimated as 93 pM, with the detection time of 40 min. Additionally, the Fresnel calculations suggested higher potential sensitivity of the current system compared to that of the conventional SPR sensors. Thus, the SNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing due to the high performance and the large potential of the surface functionality.
authors.affiliation: Institute of Optical Imaging and Sensing, Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzen 518055, China; Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Fan
authors.affiliation: Institute of Optical Imaging and Sensing, Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzen 518055, China; Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Institute of Optical Imaging and Sensing, Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzen 518055, China; Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Ma
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Teramae
authors.affiliation: Institute of Optical Imaging and Sensing, Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzen 518055, China. Electronic address: sun.shuqing@sz.tsinghua.edu.cn.
authors.forename: Shuqing
authors.initials: S
authors.lastname: Sun
authors.affiliation: Institute of Optical Imaging and Sensing, Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzen 518055, China.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: He
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013194:Staining and Labeling / Q000379:methods; D019809:Streptavidin / Q000032:analysis*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D012822:Silicon Dioxide; D019809:Streptavidin
keywords: Biosensors; Label-free biosensing; Nanotube arrays; Optical waveguide; Porous anodic alumina; Silica