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Journal of Biomedical Optics

Birefringence of a normal human red blood cell and related optomechanics in an optical trap
Author(s): Belavadi Venkatakrishnaiah Nagesh; . Yogesha; Ramarao Pratibha; Praveen Parthasarathi; Shruthi Subhash Iyengar; Sarbari Bhattacharya; Sharath Ananthamurthy
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Paper Abstract

A normal human red blood cell (RBC) when trapped with a linearly polarized laser, reorients about the electric polarization direction and then remains rotationally bound to this direction. This behavior is expected for a birefringent object. We have measured the birefringence of distortion-free RBCs in an isotonic medium using a polarizing microscope. The birefringence is confined to the cell’s dimple region and the slow axis is along a diameter. We report an average retardation of 3.5±1.5  nm for linearly polarized green light (λ=546  nm). We also estimate a retardation of 1.87±0.09  nm from the optomechanical response of the RBC in an optical trap. We reason that the birefringence is a property of the cell membrane and propose a simple model attributing the origin of birefringence to the phospholipid molecules in the lipid bilayer and the variation to the membrane curvature. We observe that RBCs reconstituted in shape subsequent to crenation show diminished birefringence along with a sluggish optomechanical response in a trap. As the arrangement of phospholipid molecules in the cell membrane is disrupted on crenation, this lends credence to our conjecture on the origin of birefringence. Dependence of the birefringence on membrane contours is further illustrated through studies on chicken RBCs.

Paper Details

Date Published: 14 November 2014
PDF: 12 pages
J. Biomed. Opt. 19(11) 115004 doi: 10.1117/1.JBO.19.11.115004
Published in: Journal of Biomedical Optics Volume 19, Issue 11
Show Author Affiliations
Belavadi Venkatakrishnaiah Nagesh, Bangalore Univ. (India)
M.S. Ramaiah Institute of Technology (India)
. Yogesha, Bangalore Univ. (India)
Ramarao Pratibha, Raman Research Institute (India)
Praveen Parthasarathi, Bangalore Univ. (India)
Shruthi Subhash Iyengar, Bangalore Univ. (India)
Sarbari Bhattacharya, Bangalore Univ. (India)
Sharath Ananthamurthy, Bangalore Univ. (India)

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