Abstract
We demonstrate the use of a double-beam optical tweezers system to stabilize red blood cell (RBC) orientation in the optical tweezers during measurements of elastic light scattering from the trapped cells in an angle range of 5-30 degrees. Another laser (He-Ne) was used to illuminate the cell and elastic light scattering distribution from the single cell was measured with a goniometer and a photomultiplier tube. Moreover, CCD camera images of RBCs with and without laser illumination are presented as complementary information. Light scattering from a RBC was measured in different fixed orientations. Light scattering from cells was also measured when the length of the cell was changed in two different orientations. Light scattering measurements from spherical and crenate RBCs are described and the results are compared with other cell orientations. Analysis shows that the measured elastic light scattering distributions reveal changes in the RBC’s orientation and shape. The effect of stretching on the changes in scattering is larger in the case of face-on incidence of He-Ne laser light than in rim-on incidence. The scattering patterns from RBCs in different orientations as well as from a spherical RBC were compared with numerical results found in literature. Good correlation was found.
Highlights
Light scattering from red blood cells (RBCs) is an important research problem and has been studied considerably
The light scattering from the RBC depends on the shape, orientation, and volume of the RBC, as well as its refractive index, which depends on the hemoglobin concentration [5,6]
In this paper we demonstrate the usability of a setup consisting of optical tweezers with two optical traps combined with a light scattering measurement system
Summary
Light scattering from red blood cells (RBCs) is an important research problem and has been studied considerably. Because of the biconcave shape and the ability of RBCs to deform, the cross-section toward an illuminating laser source varies This variation makes it difficult to determine the exact mean cell volume [10]. Optical tweezers have been combined with other measurement instruments, such as light scattering goniometers [28,29,30] and a Raman spectrometer [31] In these studies, single cells and particles are kept still under the microscope objective with laser tweezers during the measurement. No optical tweezers with enough axial trapping force were combined with the IRAM system to control the orientation of the sample cell [33]. We discuss the effect of an osmotic environment on the RBC’s shape and light scattering properties at the single-cell level. The results are discussed in relation to published simulation and experimental results found in literature
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