Research Center for Spatio Temporal Biological Network

Tokyo, Japan

Research Center for Spatio Temporal Biological Network

Tokyo, Japan

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Ko P.J.,Tokyo Institute of Technology | Ko P.J.,Research Center for Spatio Temporal Biological Network | Ishikawa R.,Tokyo Institute of Technology | Ishikawa R.,Research Center for Spatio Temporal Biological Network | And 8 more authors.
Nanoscience and Nanotechnology Letters | Year: 2011

Biosensing platforms based on functionalized submicron-sized superparamagnetic beads (SPBs) that act as magnetic labels are being extensively researched for applications involving portable, rapid, easy-to-use and highly sensitive point-of-care medical testing (POCT) equipment. Recently, in order to achieve greater sensitivity and improved quantification, there have been increasing demands for the use of SPBs with diameters of less than 300 nm. However, the detection of low densities of sub-250 nm diameter SPBs using typical magnetoresistive-based biosensors is extremely challenging due to the intrinsic noise that affects these devices, as well as the weak magnetic signals that are derived from nano-sized SPBs. Here, we demonstrate an easy, quick, and economical method for the detection of small numbers of SPBs by optically monitoring the intensity of light that is reflected back from porous silicon photonic crystals (multi-layer-PSi) in less than 60 seconds. Copyright © 2011 American Scientific Publishers. All rights reserved.


Ko P.J.,Tokyo Institute of Technology | Ko P.J.,Research Center for Spatio Temporal Biological Network | Takamura T.,Tokyo Institute of Technology | Takamura T.,Research Center for Spatio Temporal Biological Network | And 2 more authors.
Journal of Physics: Conference Series | Year: 2012

Optically monitoring biosensing procedures based on the dynamics of an aqueous solution containing functionalized superparamagnetic beads in the application of the external rotating magnetic field has been developed for a rapid, highly sensitive, and inexpensive bioassay. Typically, the dynamics of micrometer diameter beads is observed by conventional optical microscopes. For greater affinity to biomolecules, there is a demand which necessitates the use of nanometer sized superparamagnetic beads, comparable size to actual biomolecules. However, a limited amount of work for monitoring the dynamics of nanometer sized beads has been performed thus far due to the maximum resolution of microscopes. Here, we propose a novel protocol enabling us monitor the dynamics of nanometer-diameter beads via change in the optical transmittance. © Published under licence by IOP Publishing Ltd.


Takamura T.,Tokyo Institute of Technology | Takamura T.,Research Center for Spatio Temporal Biological Network | Morimoto Y.,Tokyo Institute of Technology | Sandhu A.,Tokyo Institute of Technology | And 2 more authors.
Japanese Journal of Applied Physics | Year: 2011

Superparamagnetic beads (SPBs) used as magnetic labels offer potential for the realization of high sensitivity and low cost biosensors for point of care treatment (POCT). For better biomolecular affinity and higher sensitivity, it is desirable to use sub-200-nm-diameter SPBs comparable in size to actual biomolecules. However, the detection of small concentrations of such SPBs by magnetoresistive devices is extremely challenging due to small magnetic response of SPBs. As a solution to these limitations, we describe a simple detecting procedure where the capture of micro-SPBs by immobilized nano-target SPBs due to self-assembly induced by an external magnetic field, which was monitored under an optical microscope. Here we describe biosensing system based on self-assembly of micro-SPBs by nanoSPBs targets using a system without external pumps, thereby enabling greater miniaturization and portability. © 2011 The Japan Society of Applied Physics.


Zahmani A.H.,Tokyo Institute of Technology | Sandhu A.,Tokyo Institute of Technology | Sandhu A.,Research Center for Spatio Temporal Biological Network | Sandhu A.,Toyohashi University of Technology
Journal of Nanoscience and Nanotechnology | Year: 2011

The potential of AlGaN/GaN heterostructures integrated with zinc oxide (ZnO) nanowires for gas sensing applications is demonstrated. Single crystal ZnO nanowires, serving as sensing probes, were selectively grown between two ohmic electrodes of AlGaN/GaN two dimensional electron gas heterostructures by thermal oxidation of sputtered zinc films in air. Electron diffraction and transmission electron microscopy showed the ZnO-nanowires to be crystalline structures oriented in the [001] direction. The fabricated structures were used to detect ethanol, acetone and methanol in a nitrogen background. The results indicate that the hybrid AlGaN/GaN-ZnO nanowires gas sensors are operable over a broad range of temperatures and could potentially be integrated with devices for wireless environmental monitoring. Copyright © 2011 American Scientific Publishers All rights reserved.

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