Yasutake Inoue

Proposal of spectroscopy-tomography of single cell

Currently, diagnosis of cancer is performed by biopsy, whereby medical doctors observe a removed specimen, focusing their attention on morphological changes in the cell sequence and cell nuclei. For early cancer, the only effect is a slight increase in the size of the cell nuclei in comparison with normal cells. Based on medical knowledge, it is presumed that an extremely small amount of a specific protein may be contained in a cell nucleus. We propose spectroscopy-tomography of single cell to measure slight changes in this protein. This technology is composed of two elemental technologies, high spatial resolution spectrometry and a precise single cell rotating method. We propose variable phase-contrast spectrometry as the high spatial resolution spectrometry and proximal two-beam optical tweezers as the precise rotating method. By these methods, we can obtain a 3-dimensional distribution of the cell components to a high spatial resolution. We verified the accuracy of variable phase-contrast spectrometry by measuring the height of a diffraction grating. We confirmed that a microsphere can be rotated by proximal two-beam optical tweezers.

6-DOF control of single living cells by proximal two-beam optical tweezers

We performed a spectroscopy-tomography study of a single living cell to obtain 3-dimensional distribution of proteins in high spatial resolution in real time. In this report, we mention the 6-DOF manipulation of a single living cell to achieve the high spatial resolution 3-dimentional spectrometry. We propose the proximal two- beam optical tweezers as rotational operation. We decided to illuminate the proximal two points in each from different directions using two beams. In this case, the light pressure generated by light absorption is made to act as rotating torque. Using this proposed method, we can operate the rotational velocity of a microsphere regardless of refractive index distribution by non-contact operation. In addition, rotational speed is controlled by optical PWM operation. This proposed optical PWM operation is that the received light intensity is changed by the illumination time. This method can be developed into the 6-DOF control of single-cell. And we propose the optical spatial filtering method, paying attention to the diffracted light that is generated from a sample, as translational velocity measurement. This measurement derives the arbitrary component of the spatial frequency from the random refracted index distribution as the periodic light intensity distribution. This periodic light intensity distribution changes in accordance with the translation of an object. Therefore, we can obtain the translational velocity of the non- labeled cell by high-response photodiode.

Variable phase-contrast spectrometry for reconstructing the 3- dimensional distribution of components in single living cells

We propose the spectroscopy-tomography of single cells to improve the early detection and treatment of cancer. This technology can obtain the 3-dimensional distribution of components at a high spatial resolution. In this paper, we mention the analysis result of the cross-sectional images of the microsphere whose diameter is 10 μm. The distribution of the internal submicron-defect in the microsphere can be analyzed. To obtain the correct 3-dimensional absorption distribution, the axial runout can not be allowed. However, the center of rotation is displaced because the cells have complex refractive index distribution. Therefore we propose the image processing that uses the normalized correlation function as estimated value. The cross-sectional image of the microsphere is improved and the vague internal defect becomes to be distinguished by this proposed method. Moreover, based on this method, the 3-dimentional refractive index distribution in a single cell is estimated and the part which has a high refractive index in the cell is distinguished clearly. And we mention the proposed variable phase-contrast spectrometry as the 2-dimensional high spatial resolution spectrometry. This proposed method is a phase-shift interferometry between the 0th order diffracted light and the higher order diffracted light. We discuss the experimental results of the spectral characteristics using the proposed variable phase-contrast spectrometry. We measured the spectral characteristics at each pixel using the color filter of the liquid crystal and verified that the 2-dimensional spectral characteristics can be measured with good result.