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    Microheater-integrated zinc oxide nanowire microfluidic device for hybridization-based detection of target single-stranded DNA
    (2021-06-18)
    Takahashi, Hiromi
    ;
    Yasui, Takao
    ;
    Kashida, Hiromu
    ;
    Makino, Koki
    ;
    Shinjo, Keiko
    Detection of cell-free DNA (cfDNA) has an impact on DNA analysis in liquid biopsies. However, current strategies to detect cfDNA have limitations that should be overcome, such as having low sensitivity and requiring much time and a specialized instrument. Thus, non-invasive and rapid detection tools are needed for disease prevention and early-stage treatment. Here we developed a device having a microheater integrated with zinc oxide nanowires (microheater-ZnO-NWs) to detect target single-stranded DNAs (ssDNAs) based on DNA probe hybridization. We confirmed experimentally that our device realized in-situ annealed DNA probes by which we subsequently detected target ssDNAs. We envision that this device can be utilized for fundamental studies related to nanobiodevice-based DNA detection.
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    Engineering Nanowire-Mediated Cell Lysis for Microbial Cell Identification
    (2019-02-26)
    Yasui, Takao
    ;
    Yanagida, Takeshi
    ;
    Shimada, Taisuke
    ;
    Otsuka, Kohei
    ;
    Takeuchi, Masaki
    Researchers have demonstrated great promise for inorganic nanowire use in analyzing cells or intracellular components. Although a stealth effect of nanowires toward cell surfaces allows preservation of the living intact cells when analyzing cells, as a completely opposite approach, the applicability to analyze intracellular components through disrupting cells is also central to understanding cellular information. However, the reported lysis strategy is insufficient for microbial cell lysis due to the cell robustness and wrong approach taken so far (i.e., nanowire penetration into a cell membrane). Here we propose a nanowire-mediated lysis method for microbial cells by introducing the rupture approach initiated by cell membrane stretching; in other words, the nanowires do not penetrate the membrane, but rather they break the membrane between the nanowires. Entangling cells with the bacteria-compatible and flexible nanowires and membrane stretching of the entangled cells, induced by the shear force, play important roles for the nanowire-mediated lysis to Gram-positive and Gram-negative bacteria and yeast cells. Additionally, the nanowire-mediated lysis is readily compatible with the loop-mediated isothermal amplification (LAMP) method because the lysis is triggered by simply introducing the microbial cells. We show that an integration of the nanowire-mediated lysis with LAMP provides a means for a simple, rapid, one-step identification assay (just introducing a premixed solution into a device), resulting in visual chromatic identification of microbial cells. This approach allows researchers to develop a microfluidic analytical platform not only for microbial cell identification including drug- and heat-resistance cells but also for on-site detection without any contamination.
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    A Free-space interferometric refractometer structure with simple microfluidic chips
    (2012-01-01)
    Sumriddetchkajorn, Sarun
    ;
    Chaitavon, Kosom
    ;
    Nukeaw, Jiti
    We introduce and experimentally demonstrate an optofluidics-based refractometer structure arranged in a simple free-space Young interferometer design. Our key idea is based on the use of a very simple microfluidic chip structure that consists of one or two flow channels arranged in parallel. We then pass the optical beam through the flow channels of the microfluidic chip. Behind the flow channels, there are two small apertures where the incident optical beam is automatically divided into two optical beams. These two optical beams are propagating in free space for a desired distance before they interfere with each other at the observation plane. Key features include simplicity in design, ease of implementation, and robustness. In the experimental demonstration, we use a 655-nm wavelength laser diode; the free-space propagation distance is 57.5 cm. The two-channel microfluidic chip has a 900-μm channel spacing, a 100-μm channel width, and a 100-μm channel depth (i.e., d/L = 9). Results indicate a sensitivity of 1.34 × 10 <sup>-4</sup> RIU in measuring the refractive index of the sucrose solution which clearly agrees with the theoretical analysis. A higher sensitivity of 6.19 × 10 <sup>-6</sup> RIU is also accomplished when the single-channel microfluidic chip with a measured d/L ratio of 0.52 is combined with an optical mask having a 600-μm channel spacing. © 2011 IEEE.