Optical tweezer for probing erythrocyte membrane deformability (original) (raw)
Related papers
Orientational dynamics of human red blood cells in an optical trap
Journal of Biomedical Optics, 2013
We report here on studies of reorientation of human red blood cells (RBCs) in an optical trap. We have measured the time required, t re , for the plane of the RBC entering the optical trap to undergo a 90-deg rotation to acquire an edge on orientation with respect to the beam direction. This has been studied as a function of laser power, P, at the trap center. The variation of t re with increasing P shows an initial sharp decrease followed by a much smaller rate of further decrease. We find that this experimentally measured variation is not in complete agreement with the variation predicted by a theoretical model where the RBC is treated as a perfectly rigid circular disk-like body. We argue that this deviation arises due to deformation of the RBC. We further reason that this feature is dominated by the elastic behavior of the RBC membrane. We compare the studies carried out on normal RBCs with RBCs where varying conditions of membrane stiffness are expected. We propose that the value of energy used for maximum deformation possible during a reorientation process is an indicator of the membrane elasticity of the system under study.
Shape anisotropy induces rotations in optically trapped red blood cells
Journal of Biomedical Optics, 2010
A combined experimental and theoretical study has been carried out to probe the rotational behaviour of red blood cells (RBCs) in a single beam optical trap. We have induced shape changes in RBCs by altering the properties of the suspension medium in which live cells float. We find that certain shape anisotropies result in the rotation of optically-trapped cells. Indeed, even normal (healthy) RBCs can be made to rotate using linearlypolarized trapping light by altering the osmotic stress the cells are subjected to. Hyperosmotic stress is found to induce shape anisotropies. We have also probed the effect of the medium's viscosity on cell rotation. The observed rotations have been modelled using a Langevin-type equation of motion that takes into account frictional forces that are generated as RBCs rotate in the medium. We observe good correlation between our measured data and calculated results.
Birefringence of a normal human red blood cell and related optomechanics in an optical trap
Journal of Biomedical Optics, 2014
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 AE 1.5 nm for linearly polarized green light (λ ¼ 546 nm). We also estimate a retardation of 1.87 AE 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.
Analysis of the behaviour of erythrocytes in an optical trapping system
Optics Express, 2000
We present a theoretical analysis of the behaviour of erythrocytes in an optical trapping system. We modeled erythrocyte behaviour in an optical trap by an algorithm which divided the cell surface into a large number of elements and recursively summed the force and torque on each element. We present a relationship between the torque and angle of orientation of the cell, showing that stable equilibrium orientations are at angles of 0 o , 180 o and 360 o and unstable equilibrium orientations are at 90 o and 270 o relative to the axis of beam propagation. This is consistent with our experimental observations and with results described in the literature.
Macromolecular Symposia, 2017
The dynamics of trapped entities in an Optical Trap (OT) can yield information with regards to their viscoelastic response as well as optical anisotropy, if any. Detailed analysis of such dynamics correlated with parameters which affect the response can yield additional clues to the exact effect of these on the trapped entities. In this work, we illustrate this point by showing how the altered behavior of Red Blood Cells (RBC) treated with Bovine Serum Albumin (BSA) yields information about the nature of action of BSA, on which there is no current consensus in literature. We conclude from our studies that BSA treatment leads to a change in the birefringence of the RBCs, a conclusion arrived at from the altered optomechanical response of such cells in a linearly polarized Gaussian beam OT. Furthermore, we argue that the observed changes in cellular optical anisotropy may be thought of as due to changes in the curvature of the RBC membrane. We also note that BSA action could help mimi...
Detection of Calcium-Induced Morphological Changes of Living Cells Using Optical Traps
IEEE Photonics Journal, 2010
In this paper, we investigate an optical-trap-based method for the detection of structural changes of the red blood cell (RBC) membrane affected by Ca 2þ ions. Individual cells are immobilized by the use of optical tweezers and are monitored live, while the concentration of Ca 2þ ions in the buffer is changed simultaneously. Ca 2þ ions are known to affect the cells' membrane morphology. These changes are attributed to the formation of calcium-induced hydrophobic aggregates of phospholipid molecules in the RBC membrane, resulting in a net change in membrane rigidity. Membrane deformation results in the change of effective radius and the drag coefficient of the cell, both of which affect the Brownian motion of the cell in solution. This motion is indirectly measurable by monitoring the forward scattering light and its dependence on the size and drag coefficient of the cell. We show the relationship between the Ca 2þ ion concentration and the optical trap specifications. The results are in agreement with previous biological studies and the phase contrast observations of living RBCs under investigation.
A biophotonic study of live, flowing red blood cells in an optical trap
Photonics 2010: Tenth International Conference on Fiber Optics and Photonics, 2010
We investigate the physics of an optically trapped red blood cell under physiological conditions. When a single, live red blood cell, is placed in an optical trap, the normal biconcave disk shaped cell is observed to undergo a folding action and thereby take up a rod like shape. If such an RBC has any shape anisotropies due to perturbation through malarial infection or hyperosmotic stress, it is observed to rotate in the linearly polarised laser field. Finally when such an optically trapped RBC is exposed to a shear flow, a tank treading like behaviour of the red blood cell membrane is visualised (wherein the RBC membrane revolves around the central body of the cell). The tank treading motion of a red blood cell held stationary in the optical trap allows for the dynamics to be viewed in a prolonged manner without the usage of earlier constraints such fast imaging system.
2018
A rapid local deformation of the erythrocyte membrane in the shape of an imprint caused by illumination with a focused laser beam in the presence of an external fluorophore has been investigated. This morphological change of the membrane appeared to be the very first observable step of the photohemolysis process which is exploited in photodynamic therapy. I showed that when a laser beam was focused on the erythrocyte membrane, the mt:mbrane was pulled toward the inside of the cell, independently of the direction in which the light was traveling. Imprint formation was observed neither on the lipid membrane )f giant unilamellar vesicles nor on the membrane of nucleated mammalian cells ~:uch as HeLa cells. It shows that the effect is specific to erythrocytes; suggesting that it might be due to the unique structure of the erythrocyte membrane cytoskeleton. Alsl), I found that the rate of the imprint formation depended on laser input power, fluorophore concentration, and the presence of ...
Stretching of red blood cells using an electro-optics trap
Biomedical Optics Express, 2014
The stretching stiffness of Red Blood Cells (RBCs) was investigated using a combination of an AC dielectrophoretic apparatus and a single-beam optical tweezer. The experiments were performed at 10 MHz, a frequency high enough to avoid conductivity losses, but below the second turnover point between positive and negative dielectrophoresis. By measuring the geometrical parameters of single healthy human RBCs as a function of the applied voltage, the elastic modulus of RBCs was determined (µ = 1.80 ± 0.5 µN/m) and compared with similar values of the literature got by other techniques. The method is expected to be an easy-touse, alternative tool to determine the mechano-elastic properties of living cells, and, on this basis, to distinguish healthy and diseased cells
Recent Progresses in Optical Trap-and-Stretch of Red Blood Cells
Biophotonics 2007: Optics in Life Science, 2007
In this paper, we briefly review earlier approaches for optical stretching of red blood cells (RBCs) and introduce a novel approach based on oscillatory optical tweezers. Preliminary experimental data for optical trap-and-stretch of RBCs by two approaches, namely the counter-propagating dual-beam trap-and-stretch and the oscillatory optical tweezers, are presented and discussed. Please verify that (1) all pages are present, (2) all figures are acceptable, (3) all fonts and special characters are correct, and (4) all text and figures fit within the margin lines shown on this review document. Return to your MySPIE ToDo list and approve or disapprove this submission.