Erythrocyte Membrane Failure by Electromechanical Stress

Abstract

We envision that electrodeformation of biological cells through dielectrophoresis as a new technique to elucidate the mechanistic details underlying membrane failure by electrical and mechanical stresses. Here we demonstrate the full control of cellular uniaxial deformation and tensile recovery in biological cells via amplitude-modified electric field at radio frequency by an interdigitated electrode array in microfluidics. Transient creep and cyclic experiments were performed on individually tracked human erythrocytes. Observations of the viscoelastic-to-viscoplastic deformation behavior and the localized plastic deformations in erythrocyte membranes suggest that electromechanical stress results in irreversible membrane failure. Examples of membrane failure can be separated into different groups according to the loading scenarios: mechanical stiffening, physical damage, morphological transformation from discocyte to echinocyte, and whole cell lysis. These results show that this technique can be potentially utilized to explore membrane failure in erythrocytes affected by other pathophysiological processes.

Keywords: cell biomechanics; cell lysis; dielectrophoresis; erythrocyte; membrane failure; microfluidics.

Figure 1

Schematic of electrostatics of biological cells in a non-uniform electric field. (a) The interactions between the electric field and the induced dipole charges at a thin ellipsoidal shell generate a net force, which acts to elongate the shell in the direction of electric field. The movement of the shell is known as dielectrophoresis. The direction of cell movement retains when the direction of field changes. (b) When the cell approaches the higher field strength and reaches an equilibrium state with no net movement, cell membrane is stretched uniaxially due to the force components in the opposite directions.

Figure 2

Experimental observations of electrodeformation of erythrocyte membranes in interdigitated electrode settings. (a) Cells are freely suspended in the medium when the electric field is off. (b) Cells are stretched by the DEP force when the electric field is supplied. (c) Representative electrodeformation of the cell membrane, d, as quantified by the maximum displacement of the cell membrane to the edge of the electrode. Insets show representative deformation of the cell membranes with time.

Figure 3

Electrodeformation of erythrocyte membranes during cyclic sinusoidal waveforms. (a) Electrical excitation was supplied to the erythrocyte suspension, each cycle consists of a duration for 4 s and a relaxation for 4 s. V_rms value is 2 V. (b) Displacement of erythrocyte membrane to the electrode edge as a function of time (n = 10) during the 1st and 450th cycles, respectively. Error bar represents the standard deviation. (c) Morphological of cells before electrodeformation and after the 1st and 450th cycles of electrodeformation.

Figure 4

Electrodeformation of erythrocyte membranes during cyclic square waveforms. (a) Electrical excitation was supplied to the erythrocyte suspension, each cycle consists of a duration for 10 s and a relaxation for 10 s. V_rms value is 2 V. (b) Displacement of erythrocyte membrane to the electrode edge as a function of time (n = 5) during the 1st and 180th cycles, respectively. Error bar represents the standard deviation. (c) Morphological of cells before electrodeformation and after the 1st and 180th cycles of electrodeformation.

Figure 5

Creep and recovery test during cyclic loading conditions. Error bar represents the standard deviation.

Figure 6

Erythrocyte response to high field strength excitations. (a) Induced membrane failure test was conducted by subjecting erythrocyte suspension to a constant high electric field strength for a duration of 22 s and removed after that. V_rms value is 7 V. (b) Such a load caused a strain in erythrocyte membranes as a function of time. It decreased gradually in an exponential function (n = 6). Error bar represents the standard deviation. (c) After the loading condition was removed, cells recovered with permanent damages in the membranes, similar to the echinocytes with small volume and thorny projections at multiple places.

Figure 7

Release of hemoglobin from erythrocytes upon the coupling of membrane electrical breakdown and the electromechanical tensile stress. (a) Time elapse of a representative erythrocyte in response to 7 V_rms excitation. (b, c) Re(f_CM) as a function of electrical frequency for erythrocytes with different interior electrical conductivity, using ellipsoid and spherical models of the same volume, respectively. The three principal axes of the ellipsoidal erythrocyte were assumed to be 5 μm, 1.5 μm, and 1.3 μm, respectively. The dashed line indicates the excitation frequency of 1.58 MHz used in this study.