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Fibrin fiber fluctuation

Citation

Hu, Qingda; Botvinick, Elliot (2021), Fibrin fiber fluctuation , Dryad, Dataset, https://doi.org/10.7280/D1ZT21

Abstract

Understanding force propagation through the fibrous extracellular matrix can elucidate how cells interact mechanically with their surrounding tissue. Presumably, due to elastic nonlinearities of the constituent filaments and their random connection topology, force propagation in fiber networks is quite complex, and the basic problem of force propagation in structurally heterogeneous networks remains unsolved. We report on a new technique to detect displacements through such networks in response to a localized force, using a fibrin hydrogel as an example. By studying the displacements of fibers surrounding a two-micron bead that is driven sinusoidally by optical tweezers, we develop maps of displacements in the network. Fiber movement is measured by fluorescence intensity fluctuations recorded by a laser scanning confocal microscope. We find that the Fourier magnitude of these intensity fluctuations at the drive frequency identifies fibers that are mechanically coupled to the driven bead. By examining the phase relation between the drive and the displacements, we show that the fiber displacements are, indeed, due to elastic couplings within the network. Both the Fourier magnitude and phase depend on the direction of the drive force, such that displacements typically propagate farther, but not exclusively, along the drive direction. This technique may be used to characterize the local mechanical response in 3-D tissue cultures, and to address fundamental questions about force propagation within fiber networks. 

Methods

Images were taken using Olympus Fluoview 1200 system with 60x oil 1.45 NA objective.

Files in OIF.zip are not processed.

Images in MATLAB.zip were generated using ImageJ 'substack' command. Updated MATLAB code can be found at this Github repository.

 

Usage Notes

Readme can be found in MATLAB.zip for instructions on how to use the matlab code.

For additional details regarding the OIF image files, please contact Elliot Botvinick.