Cooperative buckling and the nonlinear mechanics of nematic semiflexible networks

Foucard, Louis; Price, June; Klug, William S.; Levine, Alex

doi:10.1088/0951-7715/28/9/r89

Cited by 9 publications

(6 citation statements)

References 65 publications

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“…The occurrences of fits with G'' < 0 indicates that the response of the system cannot be interpreted as being linear in the applied force. The presence of these nonlinear rheological effects of the intra-and interfibrillar cross-linking despite no detectable change in microstructure is consistent with nonlinear response of nematically aligned fiber networks (24) and will be a basis for further investigation.…”

Section: Discussionsupporting

confidence: 59%

Cell contact guidance via sensing anisotropy of network mechanical resistance

Thrivikraman

Jagiełło

Lai

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Despite the ubiquitous importance of cell contact guidance, the signal-inducing contact guidance of mammalian cells in an aligned fibril network has defied elucidation. This is due to multiple interdependent signals that an aligned fibril network presents to cells, including, at least, anisotropy of adhesion, porosity, and mechanical resistance. By forming aligned fibrin gels with the same alignment strength, but cross-linked to different extents, the anisotropic mechanical resistance hypothesis of contact guidance was tested for human dermal fibroblasts. The cross-linking was shown to increase the mechanical resistance anisotropy, without detectable change in network microstructure and without change in cell adhesion to the cross-linked fibrin gel. This methodology thus isolated anisotropic mechanical resistance as a variable for fixed anisotropy of adhesion and porosity. The mechanical resistance anisotropy |Y*|−1 − |X*|−1 increased over fourfold in terms of the Fourier magnitudes of microbead displacement |X*| and |Y*| at the drive frequency with respect to alignment direction Y obtained by optical forces in active microrheology. Cells were found to exhibit stronger contact guidance in the cross-linked gels possessing greater mechanical resistance anisotropy: the cell anisotropy index based on the tensor of cell orientation, which has a range 0 to 1, increased by 18% with the fourfold increase in mechanical resistance anisotropy. We also show that modulation of adhesion via function-blocking antibodies can modulate the guidance response, suggesting a concomitant role of cell adhesion. These results indicate that fibroblasts can exhibit contact guidance in aligned fibril networks by sensing anisotropy of network mechanical resistance.

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Section: Discussionsupporting

confidence: 59%

Cell contact guidance via sensing anisotropy of network mechanical resistance

Thrivikraman

Jagiełło

Lai

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…3d which depicts a typical example at = 0.5%. The correspondence between strain stiffening and the increase in ∆ + is consistent with previous work, which found that similar non-linearity was required for asymmetric response to strain in simulated actin networks [12]. It therefore makes sense that the onset of strain stiffening and hysteresis occur at the same concentration.…”

Section: Dependence On Cross-linker Concentrationsupporting

confidence: 89%

“…While filament stretching dominates the mechanics of strain stiffening, filaments can also buckle under shear, creating a locally weakened region [11,12]. Changes in cross-linker concentration or filament orientation can influence the relative likelihood of shear-induced bending and stretching, impacting the mechanical response [12][13][14][15]. The physical properties of cross-linkers, such as their length and flexibility, also influences network structure and mechanics [16].…”

Section: Introductionmentioning

confidence: 99%

Actin filament alignment causes mechanical hysteresis in cross-linked networks

Scheff

Redford

Lorpaiboon

et al. 2021

Preprint

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Cells dynamically control their material properties through remodeling of the actin cytoskeleton, an assembly of cross-linked networks and bundles formed from the biopolymer actin. We recently found that cross-linked networks of actin filaments reconstituted in vitro can exhibit adaptive behavior and thus serve as a model system to understand the underlying mechanisms of mechanical adaptation of the cytoskeleton. In these networks, training, in the form of applied shear stress, can induce asymmetry in the nonlinear elasticity. Here, we explore control over this mechanical hysteresis by tuning the concentration and mechanical properties of cross-linking proteins in both experimental and simulated networks. We find that this effect depends on two conditions: the initial network must exhibit nonlinear strain stiffening, and filaments in the network must be able to reorient during training. Hysteresis depends strongly and non-monotonically on cross-linker concentration, with a peak at moderate concentrations. In contrast, at low concentrations, where the network does not strain stiffen, or at high concentrations, where filaments are less able to rearrange, there is little response to training. Additionally, we investigate the effect of changing cross-linker properties and find that longer or more flexible cross-linkers enhance hysteresis. Remarkably plotting hysteresis against alignment after training yields a single curve regardless of the physical properties or concentration of the cross-linkers.

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“…The buckling of semiflexible networks at small compressive strains thus induces a rich and complex mechanical behaviour of biopolymer systems and cellular materials (Foucard et al 2015). The buckling instability in swelling or shrinking hydrogels usually occurs in the poorly connected regions near the free surface in the form of wrinkles and propagate later within the drained network since a crosslinked microsctructure becomes unstable when the volume change is too large (Doi 2009).…”

Section: Discussionmentioning

confidence: 99%