Mechanical Characterization of Human Red Blood Cells Under Different Osmotic Conditions by Robotic Manipulation With Optical Tweezers

Abstract

The physiological functions of human red blood cells (RBCs) play a crucial role to human health and are greatly influenced by their mechanical properties. Any alteration of the cell mechanics may cause human diseases. The osmotic condition is an important factor to the physiological environment, but its effect on RBCs has been little studied. To investigate this effect, robotic manipulation technology with optical tweezers is utilized in this paper to characterize the mechanical properties of RBCs in different osmotic conditions. The effectiveness of this technology is demonstrated first in the manipulation of microbeads. Then the optical tweezers are used to stretch RBCs to acquire the force-deformation relationships. To extract cell properties from the experimental data, a mechanical model is developed for RBCs in hypotonic conditions by extending our previous work , and the finite element model is utilized for RBCs in isotonic and hypertonic conditions. Through comparing the modeling results to the experimental data, the shear moduli of RBCs in different osmotic solutions are characterized, which shows that the cell stiffness increases with elevated osmolality. Furthermore, the property variation and potential biomedical significance of this study are discussed. In conclusion, this study indicates that the osmotic stress has a significant effect on the cell properties of human RBCs, which may provide insight into the pathology analysis and therapy of some human diseases.

Biophysical characterization of hematopoietic cells from normal and leukemic sources with distinct primitiveness

“…With this technology, we and others have examined the deformability of erythrocytes at physiological and pathological states. 8,[13][14][15] In this study, we hypothesize that hematopoietic cells at different hierarchical stages during normal and leukemic differentiation might exhibit distinctive biophysical properties. If so, the information could provide us with another dimension by which these cellular processes can be interrogated in the future.…”

“…[12][13][14] Specifically, the amount of force (in pico-Newton) applied to a cell and the degree to which it is deformed (in nanometers) can provide information about its mechanical compliance. With this technology, we and others have examined the deformability of erythrocytes at physiological and pathological states.…”

“…Under isotonic condition, both populations could not be stretched with optical tweezers, consistent with the results obtained from UCB CD34 þ cells. In hypotonic conditions, both CD34 þ CD38 À and CD34 þ CD38 þ populations exhibited significantly cell softening and more percentage of cells became stretchable when the tonicity decreased, 14 particularly in the CD34 þ CD38 À cells [P < 0.05, 16 Fig. 1(a)].…”

“…We further characterized and compared the biophysical properties of UCB CD34 þ CD38 À and CD34 þ CD38 þ cells as well as leukemic CD33 þ CD34 þ and CD33 þ CD34 À myeloblasts, based on a continuum biomechanical model, 14,17,18 where membrane tensions are linearly related to the biophysical parameter of cells, e.g., the elastic area compressibility modulus k a . 18 The distributions of stiffness of these cell populations in both isotonic and hypotonic conditions were all fitted by Gaussian functions.…”

Detecting Swelling States of Red Blood Cells by “Cell–Fluid Coupling Spectroscopy”

“…RBCs were exposed to solutions of different tonicity to induce cell swelling and therefore a controllable and reproducible difference between the cells in each blood sample 35, 36. Changing the tonicity also induces a change in cell stiffness and shape depending on the swelling state without the need of drug treatment or biochemical modification 35, 37.…”