Measuring the Modulus and Reverse Percolation Transition of a Degrading Hydrogel

Schultz, Kelly M.; Baldwin, Aaron D.; Kiick, Kristi L.; Furst, Eric M.

doi:10.1021/mz300106y

Cited by 32 publications

(70 citation statements)

References 22 publications

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“…When α → 0, probe particles are completely arrested in the gel network. All values of α between 0 and 1 are an elastic solid or viscoelastic liquid, and this transition is defined by the critical relaxation exponent, n. The value of n has been previously determined from measurements of the kinetics of degradation analyzed using time-cure superposition (30)(31)(32)(33). To determine the state of a material, α is compared with n; if α > n, the material is a viscoelastic fluid, and if α < n, the material is an elastic solid (30).…”

Section: Resultsmentioning

confidence: 99%

Measuring dynamic cell–material interactions and remodeling during 3D human mesenchymal stem cell migration in hydrogels

Schultz

Kyburz

Anseth

2015

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

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154

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Biomaterials that mimic aspects of the extracellular matrix by presenting a 3D microenvironment that cells can locally degrade and remodel are finding increased applications as wound-healing matrices, tissue engineering scaffolds, and even substrates for stem cell expansion. In vivo, cells do not simply reside in a static microenvironment, but instead, they dynamically reengineer their surroundings. For example, cells secrete proteases that degrade extracellular components, attach to the matrix through adhesive sites, and can exert traction forces on the local matrix, causing its spatial reorganization. Although biomaterials scaffolds provide initially well-defined microenvironments for 3D culture of cells, less is known about the changes that occur over time, especially local matrix remodeling that can play an integral role in directing cell behavior. Here, we use microrheology as a quantitative tool to characterize dynamic cellular remodeling of peptide-functionalized poly(ethylene glycol) (PEG) hydrogels that degrade in response to cell-secreted matrix metalloproteinases (MMPs). This technique allows measurement of spatial changes in material properties during migration of encapsulated cells and has a sensitivity that identifies regions where cells simply adhere to the matrix, as well as the extent of local cell remodeling of the material through MMP-mediated degradation. Collectively, these microrheological measurements provide insight into microscopic, cellular manipulation of the pericellular region that gives rise to macroscopic tracks created in scaffolds by migrating cells. This quantitative and predictable information should benefit the design of improved biomaterial scaffolds for medically relevant applications.PEG-peptide hydrogels | human mesenchymal stem cells | cell migration | microrheology

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Section: Resultsmentioning

confidence: 99%

Measuring dynamic cell–material interactions and remodeling during 3D human mesenchymal stem cell migration in hydrogels

Schultz

Kyburz

Anseth

2015

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

Self Cite

154

192

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“…In principle, the removal of connections, rather than their addition, does not qualitatively change the percolation picture. For example, in the process of hydrogel degradation [6][7][8][9] connections are severed mostly uniformly in space, and the measured elastic and rheological properties [10,11] resemble the gel formation process in reverse [12].…”

Section: Introductionmentioning

confidence: 99%

Percolation of sites not removed by a random walker in d dimensions

Kantor

Kardar

2019

Phys. Rev. E

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How does removal of sites by a random walk lead to blockage of percolation? To study this problem of correlated site percolation, we consider a random walk (RW) of N = uL d steps on a d-dimensional hypercubic lattice of size L d (with periodic boundaries). We systematically explore dependence of the probability Π d (L, u) of percolation (existence of a spanning cluster) of sites not removed by the RW on L and u. The concentration of unvisited sites decays exponentially with increasing u, while the visited sites are highly correlated -their correlations decaying with the distance r as 1/r d−2 (in d > 2). On increasing L, the percolation probability Π d (L, u) approaches a step function, jumping from 1 to 0 when u crosses a percolation threshold uc that is close to 3 for all 3 ≤ d ≤ 6. Within numerical accuracy, the correlation length associated with percolation diverges with exponents consistent with ν = 2/(d − 2). There is no percolation threshold at the lower critical dimension of d = 2, with the percolation probability approaching a smooth function Π2(∞, u) > 0. PACS numbers: 05.70.Jk 05.40.Fb 68.35.Rh 36.20.Ey

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“…381 Microrheology has been also used to monitor evolution of the hydrogel modulus in situ during degradation. 382 …”

Section: Discussionmentioning

confidence: 99%