We developed a new theory-based azimuthal phase retardation microscope to visualize distributions of actin filaments in biological cells without having them with exogenous dyes, fluorescence labels, or stains. The azimuthal phase retardation microscope visualizes distributions of actin filaments by measuring the intensity variations of each pixel of a charge coupled device camera while rotating a single linear polarizer. Azimuthal phase retardation δ between two fixed principal axes was obtained by calculating the rotation angles of the polarizer at the intensity minima from the acquired intensity data. We have acquired azimuthal phase retardation distributions of human breast cancer cell, MDA MB 231 by our microscope and compared the azimuthal phase retardation distributions with the fluorescence image of actin filaments by the commercial fluorescence microscope. Also, we have observed movement of human umbilical cord blood derived mesenchymal stem cells by measuring azimuthal phase retardation distributions.
We propose a new, simple theory-based, accurate polarization microscope for birefringence imaging of cytoskeletal structures of biological cells. The new theory lets us calculate very easily the phase retardation and the orientation of the principal axis of a particular area of a biological living cell in media by simply measuring the intensity variation of a pixel of a CCD camera while rotating a single polarizer. Just from the measured intensity maxima and minima, the amount of phase retardation between the fast and the slow axis of the sample area is obtained with an accuracy of 5.010±0.798×10−3 rad. The orientation of the principal axis is calculated from the angle of the polarizer for the intensity maximum. We have compared our microscopes with two previously reported polarization microscopes for birefringence imaging of cytoskeletal structures and demonstrated the utility of our microscope with the phase retardation and orientation images of weakly invasive MCF7 and highly invasive MDA MB 231 human breast cancer cells as an example.
A novel and simplest polarization microscope by single polarization modulation method to visualize cytoskeletal
structure in bio-cells have been developed. The polarization microscope visualizes cytoskeletal structure based on
birefringence characteristics of cells. In the polarization microscope, a series of intensity images according to single
modulation of rotating linear polarizer were obtained to visualize cytoskeletal structure. Phase retardation and principal
axis orientation were calculated by analytic data processing from the acquired intensity images. Phase retardation and
principal axis orientation of breast cancer cells, MCF 7 and MDA MB 231 were measured and visualized as their
birefringence characteristics by the polarization microscope. Phase retardation sensitivity of the polarization microscope
system also was measured in this paper.