[OPTICAL REVIEW Vol. 14, No. 4 (2007) 161-164]
© 2007 The Optical Society of Japan

A Method for Measuring the Three-Dimensional Refractive-Index Distribution of Single Cells Using Proximal Two-Beam Optical Tweezers and a Phase-Shifting Mach–Zehnder Interferometer

Toshiki YASOKAWA, Ichirou ISHIMARU, Masahiro KONDO, Shigeki KURIYAMA1, Tsutomu MASAKI1, Kaoru TAKEGAWA2, and Naotaka TANAKA2

Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396, Japan
1Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0793, Japan
2Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan

(Received December 1, 2006; Accepted April 4, 2007)

This paper describes a method for measuring the three-dimensional (3D) refractive-index distribution in a single cell. The method can be used to observe the distribution of cell components without fluorescence staining. The two-dimensional optical path length distributions from multiple directions are obtained by non-contact rotation of the cell. These optical path lengths are converted into the line integrals of the refractive index, and the 3D refractive-index distribution is reconstructed by means of computed tomography. The refractive-index distribution in a breast cancer cell can be measured using a phase-shifting Mach–Zehnder interferometer in conjunction with proximal two-beam optical tweezers.

Key words: cell, refractive index, three-dimensional imaging, computed tomography, rotation, optical tweezers, light pressure, phase shift interferometer, Mach–Zehnder interferometer