Characterizing the viscoelastic properties of thin hydrogel-based constructs for tissue engineering applications

Ahearne, Mark; Yang, Ying; Haj, Alicia J. El; Then, K.; Liu, Kuo-Kang

doi:10.1098/rsif.2005.0065

Cited by 265 publications

(221 citation statements)

References 36 publications

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“…When hydrogel materials are fully swollen, their mechanical behavior can be considered similar to rubber-like materials (Anseth et al 1996), which have a Poisson ratio close to 0.5, and this value is used for e.g. alginate gels (Ahearne et al 2005). Using this value for the Poisson's ratio and the G 0 value from the last data points in Fig.…”

Section: Resultsmentioning

confidence: 99%

Controlling the elastic modulus of cellulose nanofibril hydrogels—scaffolds with potential in tissue engineering

et al. 2014

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Cellulose nanofibrils (CNF) form hydrogels at low concentrations. These hydrogels are held together by transient interactions such as entanglement of fibrils, non-specific ionic interactions and hydrogen bonds; and are thus vulnerable for changes in the chemical environment or the influence of mechanical forces. By a covalent crosslinking of the fibrils, stable permanent gels can be formed. In this study we have produced CNF by using TEMPO mediated oxidation followed by fibrillation. During this procedure, carboxyl and aldehyde groups are introduced on the CNF surfaces. The aldehyde groups are suitable sites for crosslinking, as aldehydes readily form covalent bonds to primary amines through formation of Schiff bases. For this purpose the diamines ethylenediamine and hexamethylenediamine, differing with four carbon atoms in the chain, were used as crosslinker molecules. The results show that by varying the concentration and length of the crosslinker molecules, the elastic modulus of the gels could be controlled. The reversible gels were in this way transformed to irreversible gels by a simple water based reaction. Controlling gel strength is one important premise for the use of CNF in applications such as tissue engineering.

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Section: Resultsmentioning

confidence: 99%

Controlling the elastic modulus of cellulose nanofibril hydrogels—scaffolds with potential in tissue engineering

et al. 2014

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“…͑11͒ is valid only for the Lorentz spectrum characteristic of the Kelvin-Voigt model, with total mass M t as defined above. Changing the model to, for example, a threeelement Zener model, 33 would require a new analysis to establish the minimum sampling frequency.…”

Section: Discussionmentioning

confidence: 99%

Material properties from acoustic radiation force step response

Orescanin

Toohey

Insana

2009

The Journal of the Acoustical Society of America

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An ultrasonic technique for estimating viscoelastic properties of hydrogels, including engineered biological tissues, is being developed. An acoustic radiation force is applied to deform the gel locally while Doppler pulses track the induced movement. The system efficiently couples radiation force to the medium through an embedded scattering sphere. A single-element, spherically-focused, circular piston element transmits a continuous-wave burst to suddenly apply and remove a radiation force to the sphere. Simultaneously, a linear array and spectral Doppler technique are applied to track the position of the sphere over time. The complex shear modulus of the gel was estimated by applying a harmonic oscillator model to measurements of time-varying sphere displacement. Assuming that the stress-strain response of the surrounding gel is linear, this model yields an impulse response function for the gel system that may be used to estimate material properties for other load functions. The method is designed to explore the force-frequency landscape of cell-matrix viscoelasticity. Reported measurements of the shear modulus of gelatin gels at two concentrations are in close agreement with independent rheometer measurements of the same gels. Accurate modulus measurements require that the rate of Doppler-pulse transmission be matched to a priori estimates of gel properties.

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“…The mechanical properties of the constructs were measured using a nondestructive spherical indentation technique, 15,16 which permitted repeated analysis of constructs over time. Hydrogel constructs were circumferentially clamped.…”

Section: Modulus Measurementmentioning

confidence: 99%

Corneal Stromal Cell Plasticity: In Vitro Regulation of Cell Phenotype Through Cell-Cell Interactions in a Three-Dimensional Model

Wilson

Yang²,

Haj³

2014

Tissue Engineering Part A

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In vivo, epithelial cells are connected both anatomically and functionally with stromal keratocytes. Co-culturing aims at recapturing this cellular anatomy and functionality by bringing together two or more cell types within the same culture environment. Corneal stromal cells were activated to their injury phenotype (fibroblasts) and expanded before being encapsulated in type I collagen hydrogels constructs. Three different epithelial-stromal co-culture methods were then examined: epithelial explant; transwell; and the use of conditioned media. The aim was to determine whether the native, inactivated keratocyte cell phenotype could be restored in vitro. Media supplementation with transforming growth factor beta-1 (TGF-b1) was then used to determine whether the inactivated stromal cells retained their plasticity in vitro and could be re-activated to the fibroblast phenotype. Finally, media supplementation with wortmannin was used to inhibit epithelial-stromal cell interactions. Two different nondestructive techniques, spherical indentation and optical coherence tomography, were used to reveal how epithelial-stromal co-culturing with TGF-b1, and wortmannin media supplementation, respectively, affect stromal cell behavior and differentiation in terms of construct contraction and elastic modulus measurement. Cell viability, phenotype, morphology, and protein expression were investigated to corroborate our mechanical findings. It was shown that activated stromal cells could be inactivated to a keratocyte phenotype via co-culturing and that they retained their plasticity in vitro. Activated corneal stromal cells that were fibroblastic in phenotype were successfully reverted to a nonactivated keratocyte cell lineage in terms of behavior and biological properties; and then back again via TGF-b1 media supplementation. It was then revealed that epithelial-stromal interactions can be blocked via the use of wortmannin inhibition. A greater understanding of stromal-epithelial interactions and what mediates them offers great pharmacological potential in the regulation of corneal wound healing, with the potential to treat corneal diseases and injury by which such interactions are vital.

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Characterizing the viscoelastic properties of thin hydrogel-based constructs for tissue engineering applications

Cited by 265 publications

References 36 publications

Controlling the elastic modulus of cellulose nanofibril hydrogels—scaffolds with potential in tissue engineering

Controlling the elastic modulus of cellulose nanofibril hydrogels—scaffolds with potential in tissue engineering

Material properties from acoustic radiation force step response

Corneal Stromal Cell Plasticity: In Vitro Regulation of Cell Phenotype Through Cell-Cell Interactions in a Three-Dimensional Model

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