The Optical Stretcher: A Novel Laser Tool to Micromanipulate Cells

Center for Nonlinear Dynamics, Department of Physics, University of Texas at Austin, Texas 78712, USA.
Biophysical Journal (Impact Factor: 3.97). 09/2001; 81(2):767-84. DOI: 10.1016/S0006-3495(01)75740-2
Source: PubMed


When a dielectric object is placed between two opposed, nonfocused laser beams, the total force acting on the object is zero but the surface forces are additive, thus leading to a stretching of the object along the axis of the beams. Using this principle, we have constructed a device, called an optical stretcher, that can be used to measure the viscoelastic properties of dielectric materials, including biologic materials such as cells, with the sensitivity necessary to distinguish even between different individual cytoskeletal phenotypes. We have successfully used the optical stretcher to deform human erythrocytes and mouse fibroblasts. In the optical stretcher, no focusing is required, thus radiation damage is minimized and the surface forces are not limited by the light power. The magnitude of the deforming forces in the optical stretcher thus bridges the gap between optical tweezers and atomic force microscopy for the study of biologic materials.

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Available from: Revathi Ananthakrishnan, Oct 06, 2015
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    • "Briefly, cells were held in between two counter propagating laser beams (λ = 1064 nm). Due to applied laser power, cells experienced both an optical force pulling on the cell membrane (σ ≈ 10Pa peak stress [16]) and an increase in temperature caused by laser light absorption ( "
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    ABSTRACT: Temperature has a reliable and nearly instantaneous influence on mechanical responses of cells. As recently published, MCF-10A normal epithelial breast cells follow the time–temperature superposition (TTS) principle. Here, we measured thermorheological behaviour of eight common cell types within physiologically relevant temperatures and applied TTS to creep compliance curves. Our results showed that superposition is not universal and was seen in four of the eight investigated cell types. For the other cell types, transitions of thermorheological responses were observed at 36 °C. Activation energies (E A) were calculated for all cell types and ranged between 50 and 150 kJ mol−1. The scaling factors of the superposition of creep curves were used to group the cell lines into three categories. They were dependent on relaxation processes as well as structural composition of the cells in response to mechanical load and temperature increase. This study supports the view that temperature is a vital parameter for comparing cell rheological data and should be precisely controlled when designing experiments.
    New Journal of Physics 07/2015; 17(7). DOI:10.1088/1367-2630/17/7/073010 · 3.56 Impact Factor
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    • "Single suspended cells are transported through a square glass capillary placed perpendicularly to the optical fibers. Two counter-propagating 'stretch laser fibers' (yellow) form the classical optical stretcher trap, where the cells can be held and stretched by optical forces [43]. In our setup, the temperature of the trapped cells can be changed quickly by laser light emission of the additional 'heat laser fibers' (red). "
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    ABSTRACT: DNA is known to be a mechanically and thermally stable structure. In its double stranded form it is densely packed within the cell nucleus and is thermo-resistant up to . In contrast, we found a sudden loss of cell nuclei integrity at relatively moderate temperatures ranging from 45 to . In our study, suspended cells held in an optical double beam trap were heated under controlled conditions while monitoring the nuclear shape. At specific critical temperatures, an irreversible sudden shape transition of the nuclei was observed. These temperature induced transitions differ in abundance and intensity for various normal and cancerous epithelial breast cells, which clearly characterizes different cell types. Our results show that temperatures slightly higher than physiological conditions are able to induce instabilities of nuclear structures, eventually leading to cell death. This is a surprising finding since recent thermorheological cell studies have shown that cells have a lower viscosity and are thus more deformable upon temperature increase. Since the nucleus is tightly coupled to the outer cell shape via the cytoskeleton, the force propagation of nuclear reshaping to the cell membrane was investigated in combination with the application of cytoskeletal drugs.
    New Journal of Physics 07/2014; 16(7):073009. DOI:10.1088/1367-2630/16/7/073009 · 3.56 Impact Factor
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    • "Measurements of cellular deformability are performed using the microfluidic optical stretcher (MOS) system provided from the Lab of Prof. Josef Kaes (University Leipzig, Germany). For a detailed description of MOS we refer to Guck et al. (2001). In brief, the MOS is based on exposing cells to two opposing rays of infrared laser light (wavelength¼ 1060 nm) which generates stretching forces on the boundaries between optically different media. "
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    ABSTRACT: Mechanical cell properties play an important role in many basic biological functions, including motility, adhesion, proliferation and differentiation. There is a growing body of evidence that the mechanical cell phenotype can be used for detection and, possibly, treatment of various diseases, including cancer. Understanding of pathological mechanisms requires investigation of the relationship between constitutive properties and major structural components of cells, i.e., the nucleus and cytoskeleton. While the contribution of actin und microtubules to cellular rheology has been extensively studied in the past, the role of intermediate filaments has been scarcely investigated up to now. Here, for the first time we compare the effects of drug-induced disruption of actin and vimentin intermediate filaments on mechanical properties of suspended NK cells using high-throughput deformability measurements and computational modeling. Although, molecular mechanisms of actin and vimentin disruption by the applied cytoskeletal drugs, Cytochalasin-D and Withaferin-A, are different, cell softening in both cases can be attributed to reduction of the effective density and stiffness of filament networks. Our experimental data suggest that actin and vimentin deficient cells exhibit, in average, 41% and 20% higher deformability in comparison to untreated control. 3D Finite Element simulation is performed to quantify the contribution of cortical actin and perinuclear vimentin to mechanical phenotype of the whole cell. Our simulation provides quantitative estimates for decreased filament stiffness in drug-treated cells and predicts more than two-fold increase of the strain magnitude in the perinuclear vimentin layer of actin deficient cells relatively to untreated control. Thus, the mechanical function of vimentin becomes particularly essential in motile and proliferating cells that have to dynamically remodel the cortical actin network. These insights add functional cues to frequently observed overexpression of vimentin in diverse types of cancer and underline the role of vimentin targeting drugs, such as Withaferin-A, as a potent cancerostatic supplement.
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