Active Micro-Rheology
Active Micro-Rheology
The optical tweezers platform SENSOCELL allows performing active & passive micro-rheology experiments in viscoelastic media like cell’s cytoplasm, hydrogels or biofilms.:
- Use our automatized and customizable built-in routines for active and passive micro-rheology assays.
- Trap native structures such as organelles or vesicles or inject microbeads to perform rheology assays inside cells.
- Obtain rheological information of the extracellular matrix or soft gels.
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Micro-rheology of soft biological samples using SENSOCELL optical tweezers.
In collaboration with the University of Barcelona.
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Summary:
In this application note, we show how the microrheology module of the SENSOCELL optical tweezers system can be used to measure the viscoelastic properties of extracellular matrices or living cells, with stiffnesses ranging from tens of Pa to several kPa and at probing frequencies up to the kHz regime.
Active & passive micro-rheology of water:glycerol mixtures and polyacrylamide gels.
The active & passive micro-rheology routine in our SENSOCELL optical tweezers system allows measuring the viscosity of liquids. In this experiment, we have added 3-micron latex beads to different water:glycerol mixtures (0%, 20%, 40%, 60% and 80% glycerol in water). For each single experiment, a bead was trapped using our optical tweezers and forced to oscillate sinusoidally with 200 nm amplitude at increasing frequencies (3Hz to 100 Hz). The calculated viscosity values were then obtained by fitting the frequency dependence of the measured loss modulus (G”).
Fig. 1 Left: example of measured loss moduli at increasing frequencies for a 40% glycerol mixture. Right: predicted versus measured viscosity values of the different mixtures (increasing viscosity values correspond to increasing glycerol percentages). Symbols indicate mean of 9 different beads probed, error bars indicate S.D.
In a smiliar fashion, active micro-rheology has been carried out inside polyacrylamide gels with embedded micrometer beads to get the complex shear moduli of polyacrylamide gels.
Fig 2. Example of the frequency-dependent behavior of the complex shear moduli of soft polyacrylamide gels. Blue symbols indicate storage modulus (G’) and red symbols indicate loss modulus (G”). Symbols are median values and error bars indicate Q1 and Q3 ranges. N = 13 beads probed for this experiment.
Active & passive micro-rheology inside cells.
Here we present some preliminary data of micro-rheology tests carried out inside mouse oocytes and mouse early embryos Samples were kindly provided by Dr. Maria Almonacid from College de France and Dr. Jean Leon Maitre from Institute Curie. For these tests, no beads were internalized. Instead, endogenous vesicles located inside the cells’ cytoplasm were optically trapped and used as probes. The vesicles were forced to oscillate sinusoidally with 200 nm amplitude at increasing frequencies (10 Hz to 100 Hz) . Below we show the frequency-dependent behavior of the complex shear moduli obtained for some of these tests.
Fig 3. Example of the frequency-dependent behaviour of the complex shear moduli data obtained for tests carried out inside the cytoplasm of mouse oocytes (left) and early mouse embryo cells (right).
Related publications:
- bioRxiv This article is a preprint