Cell membrane force measurements
Cell membrane force, tension and stiffness measurements
SENSOCELL will allow you to perform cell membrane tether pulling experiments with cultured cells & explants to assess their mechanical properties and local cell membrane tension. Automatize your custom tether pulling experiments with LightAce’s programmable routines in a simple and easy way. Measure the local cell membrane stiffness by performing indentation tests with external microspheres. Apply cell membrane deformations or carry out cell stretching experiments exerting optical trapping forces directly on the cell membrane itself or using adhered microspheres as handles while simultaneously measuring the forces for each optical trap used in the experiment.
Application example 1. Membrane tether pulling on neurons and HELA cells.
Application example 2. Cell stretching by applying forces directly on the cell membrane in a dual trap experiment.
Related Application: apply a local tension to activate mechanosensitive ion channels. >> see more
Using IMPETUX’s SENSOCELL optical tweezers platform, a membrane tether pulling experiment was performed by adhering a 1 µm optically trapped fluorescent bead to a neuron. When the adhered bead is pulled away, a lipid filament (tether) is extruded from the cell surface (Fig.1).
Fig.1 Top; scheme of a tether pulling experiment performed on a neuron. Bottom: back and forth motion of a trapped fluorescent bead moving towards a neuron axon in one of the experiments.
The cell membrane tether is elongated during consecutive pulling steps producing force peaks. After each pulling step, the bead is kept fixed for a certain period of time. During this time, the cell adds material to the membrane tether and the force signal decays. Different pulling rates can be applied at subsequent steps using SENSOCELL’s customizable routines. The system monitors the applied cell membrane force and bead position at real time.
Cell membrane force measurements in tether pulling experiments
Below, Fig. 2 shows the force and trap position data for each subsequent pulling and relaxation steps. In this case, the tether is pulled at increasing speeds to produce force peaks of increasing height. A model (Datar et al. Biophys J. 2015 Feb 3; 108(3): 489–497) is used to fit the force decay response during relaxation and extract information such as the local cell membrane tension.
Fig. 2 Force and trap position signal during a tether pulling experiment performed on a neuron axon. The pulling rate is increased for each subsequent step. Fitting of force data during the relaxation process after each pulling step is shown in red.
The same type of experiment was performed on HELA cancer cells. Fig. 3 shows the formed membrane tether generated from a HELA cancer cell and attached to the pulling bead.
Fig. 3 Membrane tether formed from a HELA cancer attached to a microsphere cell during an experiment.
Similarly, Fig. 4 shows the force and trap position data obtained two different experiments performed on HELA cancer cells (blue and red data are for high and low pulling rates respectively). Note that the force signal has negative sign due to the chosen pulling direction.
Fig. 4 Force and trap position data obtained during two different (blue and red data) experiments performed on a HELA cancer cells. The applied pulling rate is higher for the blue data than for the red data.
Cell membrane tether pulling video
Custom pulling trajectories with LightAce
Cell stretching by applying forces directly on the cell membrane in a dual trap experiment
In house R&D
In this example, we show a cell stretching experiment performed on a yeast cell. The experiment is done in three steps as shown in Fig. 1. No beads were used for trapping and stretching the cell. Optical trapping forces can be applied over trappable cellular structures, in this case the cell membrane itself, and directly measured by our force spectroscopy technology without needing any previous calibration.
Cell stretching video. Forces are applied directly on the cell membrane
The following figure plots the obtained applied force vs. stretch ratio data, showing a s-shaped curve behavior typical of viscoelastic materials.
Fig. 2 Applied force vs stretch ratio for a yeast cell stretching experiment.
Other publications related with cell membrane forces or membrane deformation experiments with our technology:
V. Venturi, F. Pezzano, F. Català-Castro, H.- M. Häkkinen, S. Jiménez-Delgado, M. Colomer-Rosell, M. Marro-Sánchez, Q. Tolosa-Ramon, S. Paz-López, M. A. Valverde, P. Loza-Alvarez, M. Krieg, S. Wieser and V. Ruprecht, “The nucleus measures shape changes for cellular proprioception to control dynamic cell behavior,” SCIENCE | 16 Oct 2020: Vol. 370, Issue 6514, eaba2644. DOI: 10.1126/science.aba2644
R. Ombid, G. Oyong, E. Cabrera, W. Espulgar, M. Saito, E. Tamiya, and R. Pobre, “In-vitro study of monocytic THP-1 leukemia cell membrane elasticity with a single-cell microfluidic-assisted optical trapping system,” Biomed. Opt. Express 11, 6027-6037 (2020).
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