Engineering Gels with Time-Evolving Viscoelasticity

Abstract

From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly on the development of substrates with varying stiffness, with a few recent contributions on time- or space-dependent substrate mechanics. This work reports on a new method for engineering dynamic viscoelastic substrates, i.e., substrates in which viscoelastic parameters can change or evolve with time, providing a tool for investigating cell response to the mechanical microenvironment. In particular, a two-step (chemical and enzymatic) crosslinking strategy was implemented to modulate the viscoelastic properties of gelatin hydrogels. First, gels with different glutaraldehyde concentrations were developed to mimic a wide range of soft tissue viscoelastic behaviours. Then their mechanical behaviour was modulated over time using microbial transglutaminase. Typically, enzymatically induced mechanical alterations occurred within the first 24 h of reaction and then the characteristic time constant decreased although the elastic properties were maintained almost constant for up to seven days. Preliminary cell culture tests showed that cells adhered to the gels, and their viability was similar to that of controls. Thus, the strategy proposed in this work is suitable for studying cell response and adaptation to temporal variations of substrate mechanics during culture.

Multi-Functionalized Self-Assembling Peptides as Reproducible 3D Cell Culture Systems Enabling Differentiation and Survival of Various Human Neural Stem Cell Lines

“…To note, the obtained values can be easily modified with further customizations of HYDROSAP depending on the regenerative application: indeed we already demonstrated that by tuning different key experimental parameters (e.g., matrix stiffness, presence of functional motifs, and/or addition of neurotrophic factors) it is possible to modulate NSCs differentiation and improve differentiation toward neuronal fate (Jain et al, 2020): for example, we showed that increments of cell proliferation rate and neuronal differentiation is inversely proportional to the matrix stiffness, while stiffness and astrocytes number directly correlated (Cunha et al, 2011;Caprini et al, 2013;Han et al, 2020;Pandamooz et al, 2020). In future experiments, it will also be interesting to assess the influence of time-evolving viscoelastic properties of hydrogels over cellular behavior (Mattei et al, 2020).…”

Determination by Relaxation Tests of the Mechanical Properties of Soft Polyacrylamide Gels Made for Mechanobiology Studies

“…It can be inferred from the data that the nature of each gel (different porosity and free volume) may explain the variations of the relaxation times found here. This also suggests that the viscosity of the medium will probably influence the mechanics of the gels bathed in it, as found in [59,60].…”

Preparation and Evaluation of New Glycopeptides Obtained by Proteolysis from Corn Gluten Meal Followed by Transglutaminase-Induced Glycosylation with Glucosamine

“…The cross-linking of proteins and conjugation of saccharides occur simultaneously in TGase-induced glycosylation. TGase catalyzes the intermolecular and intramolecular protein cross-linking reactions between lysine and glutamine via acyl transfer, a process widely applied in the meat and dairy industries to improve gelation and protein texture [10], as well as varying the viscoelastic and rheological properties of the obtained products [11]. Controlling protein cross-linking is beneficial to saccharide conjugation.…”