Elastic property of sickle cell anemia and sickle cell trait red blood cells.

Endris Muhammed,Daniel Erenso,Daniel Devito,Maria Del Pilar Aguinaga,James Cooper,Horace Crogman,Robert Mushi

doi:10.1117/1.jbo.26.9.096502

Abstract

.Significance: We introduce a model for better calibration of the trapping force using an equal but oppositely directed drag force acting on a trapped red blood cell (RBC). We demonstrate this approach by studying RBCs’ elastic properties from deidentified sickle cell anemia (SCA) and sickle cell trait (SCT) blood samples.Aim: A laser trapping (LT) force was formulated and analytically calculated in a cylindrical model. Using this trapping force relative percent difference, the maximum (longitudinal) and minimum (transverse) radius rate and stiffness were used to study the elasticity.Approach: The elastic property of SCA and SCT RBCs was analyzed using LT technique with computer controlled piezo-driven stage, in order to trap and stretch the RBCs.Results: For all parameters, the results show that the SCT RBC samples have higher elastic property than the SCA RBCs. The higher rigidity in the SCA cell may be due to the lipid composition of the membrane, which was affected by the cholesterol concentration.Conclusions: By developing a theoretical model for different trapping forces, we have also studied the elasticity of RBCs in SCT (with hemoglobin type HbAS) and in SCA (with hemoglobin type HbSS). The results for the quantities describing the elasticity of the cells consistently showed that the RBCs in the SCT display lower rigidity and higher deformability than the RBCs with SCA.

Highlights

Several experimental approaches such as rheoscopy, flow channels, ektacytometry, and atomic force microscopy (AFM) have been used to study red blood cell (RBC) deformability, with each technique having its unique strengths and limitations
This paper introduces a model for better calibration of the trapping force using an equal but oppositely directed drag force acting on a trapped RBC
The stiffness k is the change of stretching force over relative change of radius for the individual HbSS and HbAS cells, which is expressed as k 1⁄4 ΔF∕ΔR, where ΔR 1⁄4 Rsheer − Rtrap

Summary

Introduction

Several experimental approaches such as rheoscopy, flow channels, ektacytometry, and atomic force microscopy (AFM) have been used to study red blood cell (RBC) deformability, with each technique having its unique strengths and limitations. Muhammed et al.: Elastic property of sickle cell anemia and sickle cell trait red blood cells for the entire RBC population, both the abnormal and normal RBCs, potentially underestimating the abnormal RBC population’s rigidity in the blood.[2] Like ektacytometry, rheoscopy measures cell deformability as a function of shear force through the microscope.[5] The mechanical property of a membrane can be determined using micropipette aspiration on lipid vesicles[6] and AFM on lipid bilayers[7] or pore-spanning membranes.[8] Micropipette aspiration experiments conducted on lipid vesicles showed that the lipid degree of saturation and the cholesterol concentration primarily affect the membrane stiffness.[9,10,11] AFM experiments showed that cholesterol and sphingolipids enhance lipid bilayers’ mechanical resistance.[12,13] Quantitative phase imaging is an optical technique that has been used to study the morphology and mechanics of RBCs13–15 and has enabled the development of non-invasive live cell imaging systems Another approach is molecular dynamics simulations, which can investigate the effect of lipid content on membrane properties. Molecular simulations have been widely used to elucidate how cholesterol and lipid types influence membrane structure and dynamics.[16,17,18] Both atomistic and coarse-grained simulations have been used to clarify the response of the membrane to the mechanical stress by applying tension to the membrane[19,20,21] or by applying an unsteady deformation to the lipid bilayer.[22]

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