Birefringence of a normal human red blood cell and related optomechanics in an optical trap

Belavadi Venkatakrishnaiah Nagesh; . Yogesha; Ramarao Pratibha; Praveen Parthasarathi; Shruthi Subhash Iyengar; Sarbari Bhattacharya; Sharath Ananthamurthy

doi:10.1117/1.JBO.19.11.115004

14 November 2014 Birefringence of a normal human red blood cell and related optomechanics in an optical trap

Belavadi Venkatakrishnaiah Nagesh, . Yogesha, Ramarao Pratibha, Praveen Parthasarathi, Shruthi Subhash Iyengar, Sarbari Bhattacharya, Sharath Ananthamurthy

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Journal of Biomedical Optics, Vol. 19, Issue 11, 115004 (November 2014). https://doi.org/10.1117/1.JBO.19.11.115004

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.

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Belavadi Venkatakrishnaiah Nagesh, . Yogesha, Ramarao Pratibha, Praveen Parthasarathi, Shruthi Subhash Iyengar, Sarbari Bhattacharya, and Sharath Ananthamurthy "Birefringence of a normal human red blood cell and related optomechanics in an optical trap," Journal of Biomedical Optics 19(11), 115004 (14 November 2014). https://doi.org/10.1117/1.JBO.19.11.115004

Published: 14 November 2014

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