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.
Micro-rheology of soft biological samples using SENSOCELL optical tweezers.
In collaboration with the University of Barcelona.
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.
Fig 1. 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.
Fig. 2. Power-law exponent obtained by fitting a structural damping model (Eq. 1) to the micro-rheology data for polyacrylamide gels. The softest gels display a liquid-like behavior while for the stiffer gels the power-law exponent saturates at 0.3. Symbols are median values and error bars indicate Q1 and Q3 ranges. N = 13 beads probed for each gel.
Active & passive micro-rheology of water:glycerol mixtures.
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”). Figure 1 shows an example of measured loss moduli at increasing frequencies for a 40% glycerol mixture.
Fig. 1 Example of measured loss moduli at increasing frequencies for a 40% glycerol mixture.
Figure 2 shows the 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.
Fig. 2 Predicted versus measured viscosity values of the different mixtures.