Narrow Results

We have developed an in-air on/off axis STIM for simultaneous density mapping with PIXE and RBS, which will be useful for damage-monitoring in cell analysis and for yield correction based on the thickness distribution of X-ray self-absorption in samples. The in-air on/off axis STIM system provides a mass concentration map in the cell analysis. In the system, a thin scattering foil is placed downstream of the sample and scattered protons are detected by a Si-PIN photodiode set at 30 degrees with respect to the beam axis. These components are set in a He-gas-filled chamber to reduce energy loss, scattering and sample damage. Using this system, areal density mapping is carried out for RBL-2H3 cells simultaneously with PIXE and RBS. Correction for self-absorption is performed and areal density map of elements is converted into a mass-concentration map using the measured matrix density. The areal density distribution of P corresponds to that of matrix and mass concentration of P is uniform in the cell region. On the other hand, Br is concentrated in the nucleus, even in the mass concentration map. The Br accumulation in the nucleus is first confirmed in mass concentration using the on/off axis STIM and PIXE system. The in-air on/off STIM system will be effective for monitoring changes in cell density during beam irradiation.

To determine the effects of microwave radiation at the molecular level as well as on the germination, growth and morphology of dry spores at the single-cell level. Dry Bacillus aryabhattai MCCC 1K02966 spores were microwave-treated at different powers and characterized using single-cell optical technology. As determined by laser tweezers Raman spectroscopy, the Ca${}^{2+}$-dipicolinic acid content increased and nucleic acid denaturation occurred in response to microwave treatment. Live-cell microscopy revealed that the germination and growth rates decreased as the microwave power increased. With respect to morphology, atomic force microscopy (AFM) demonstrated that spores became wrinkled and rough after microwave treatment. Furthermore, spores became smaller as the microwave power increased. Microwave treatment can damage DNA, and high-power microwaves can inhibit the germination of spores and reduce spore volumes. These results provide a new perspective on the responses of living single cells to microwave radiation and demonstrate the application of various new techniques for analyses of microorganisms at the single-cell level.

Microfluidic systems have been widely utilized in high-throughput biology analysis, but the difficulties in liquid manipulation and cell cultivation limit its application. This work has developed a new digital microfluidic (DMF) system for on-demand droplet control. By adopting an extending-depth-of-field (EDoF) phase modulator to the optical system, the entire depth of the microfluidic channel can be covered in one image without any refocusing process, ensuring that 95% of the particles in the droplet are captured within three shots together with shaking processes. With this system, suspension droplets are generated and droplets containing only one yeast cell can be recognized, then each single cell is cultured in the array of the chip. By observing their growth in cell numbers and the green fluorescence protein (GFP) production via fluorescence imaging, the single cell with the highest production can be identified. The results have proved the heterogeneity of yeast cells, and showed that the combined system can be applied for rapid single-cell sorting, cultivation, and analysis.