Quantitative evaluation of erythrocyte viscoelastic properties from diffractometric data: Applications to hereditary spherocytosis and hemoglobinopathies

Abstract

A numerical process is proposed to evaluate viscoelastic properties of mammalian erythrocyte membranes from diffractometric data obtained with the Erythrodeformeter (1). The numerical process is based on an idealized model of the cell response to the applied fluid shear stress assuming that the tank treading motion start lags the start of the shear stress field by several milliseconds. Photometric readings performed on the elliptical diffraction pattern generated by the shear elongated cells and photometrically recorded curves of creep and recovery of cells, are used in the calculations of rheological properties, averaged over several millions of cells. Results obtained from different hematological disorders are presented and compared with those obtained from healthy donors, showing significative differences that are in accordance with the type and the state of the corresponding disease. Computed values representative of the elastic modulus of normal cells agree very well with those ones determined with the micropipette technique (2) while retardation time, and consequently values of surface viscosity, obtained by the diffractometric technique are somewhat smaller than the ones obtained by the shape recovery in micropipettes.