Masayuki Ono

Prototype of Atomic Force Cantilevered SNOM Based on Through-The-Lens-Type Optical Lever and Polarized Illumination and Detection System

Atomic force cantilevered scanning near-field optical microscopy (ANOM) has been proposed for observing a micromagnetic structure of a recorded magneto-optical (MO) disc. The prototype system has an ability to obtain both atomic force microscopy (AFM) and scanning near-field microscopy (SNOM) images simultaneously. This system has some special functions: (1) it keeps the sample-probe gap constant with atomic force and an AFM cantilever, (2) it generates near-field light from the small aperture formed on the tip of the cantilever, (3) it uses a polarized light in the laser beam illumination and detection systems, and (4) it adjusts laser beams incident on fixed positions of the cantilever in ANOM optics. As an experimental result, we obtained SNOM and contact mode AFM images of a commercial MO disc. We can detect a polarized plane at a minimum angle of less than 0.2 deg. and observe submicron recorded magnetic domains on a 640 MB MO disc.

Effect of Firing Temperature on Composition and Phase in Pb(Co1/3Nb2/3)O3-PbTiO3-PbZrO3 Ceramics

We studied the firing temperature dependence of ceramic bulk density, composition and crystal phase in Pb(Co 1/3 Nb 2/3 )O 3 -PbTiO 3 -PbZrO 3 ceramics to clarify the origin of their semiconducting properties. The low resistivity and large dielectric loss of the ceramics were due to B-site vacancies resulting from Co vaporization during firing. An addition of CoO to the stoichiometric ceramic compositions inhibited the vaporization and the production of a pyrochlore phase in the perovskite phase. The A-site vacancies were produced by adding excess Co at higher firing temperatures, whereby the vacancies resulted from the change in Co valence with increasing firing temperature. The dependence of resistivity and dielectric loss in the ceramics on firing temperature was well explained by the compensation between the B-site vacancies and the change in valence of Co (Co 2+ →Co 3+ ).

Ultrahigh-Sensitivity Biomarker Sensing System Based on the Combination of Optical Disc Technologies and Nanobead Technologies

The detection of biomarkers in body fluids is useful for the early detection of diseases or preventive medical care. Various types of equipment that detect biomarkers have been developed and used for various occasions. It is expected that further improvement of the detection sensitivity of biomarkers will enable the extension for their applications to various diseases. In this paper, we propose a new biomarker sensing system with higher sensitivity. In the system, by combining optical disc technologies and nanobead technologies, we developed a new sensing method. Target biomarkers are specifically immobilized onto the optical disc surface through an antigen-antibody reaction, then the nanobeads are immobilized on top of the biomarkers. Since the biomarkers and beads bind to each other one-on-one, the number of target biomarkers can be measured by counting the number of nanobeads using an optical pickup. The most significant advantage of this method is that measurement can be carried out in a fully digital scheme, in contrast to current sensing systems which measure light intensity in an analog scheme.

Holographic Data Storage Media Employing Phase-Change Reflector

We have proposed a novel structure of holographic data storage media, employing a phase-change (PC) reflector for optical disc applications. The PC layer, which is initially amorphous and has a low reflectivity in a write process, works as an absorber and inhibits reflected stray beam exposure. After the write process, the PC layer is crystallized and its reflectivity is switched to a high state, realizing a sufficient signal beam intensity in a read process. Experimental results show a low noise and a high signal-to-noise ratio, and a potential to have a large multiplexing number in the PC reflector.

Development of a Highly Sensitive Device for Counting the Number of Disease-Specific Exosomes in Human Sera

BACKGROUND Although circulating exosomes in blood play crucial roles in cancer development and progression, difficulties in quantifying exosomes hamper their application for reliable clinical testing. By combining the properties of nanobeads with optical disc technology, we have developed a novel device named the ExoCounter to determine the exact number of exosomes in the sera of patients with various types of cancer. METHOD In this system, individual exosomes were captured in the groove of an optical disc coated with antibodies against exosome surface antigens. The captured exosomes were labeled with antibody-conjugated magnetic nanobeads, and the number of the labeled exosomes was counted with an optical disc drive. RESULTS We showed that the ExoCounter could detect specific exosomes derived from cells or human serum without any enrichment procedures. The detection sensitivity and linearity with this system were higher than those with conventional detection methods such as ELISA or flow cytometry. In addition to the ubiquitous exosome markers CD9 and CD63, the cancer-related antigens CD147, carcinoembryonic antigen, and human epidermal growth factor receptor 2 (HER2) were also used to quantify cancer cell line-derived exosomes. Furthermore, analyses of a cross-sectional cohort of sera samples revealed that HER2-positive exosomes were significantly increased in patients with breast cancer or ovarian cancer compared with healthy individuals and those with noncancer diseases. CONCLUSIONS The ExoCounter system exhibits high performance in the direct detection of exosomes in cell culture and human sera. This method may enable reliable analysis of liquid biopsies.