Compressional stress stiffening & softening of soft hydrogels - how to avoid artefacts in their rheological characterisation

Ferraro, R., Guido, S., Caserta, S. and Tassieri, M. (2023) Compressional stress stiffening & softening of soft hydrogels - how to avoid artefacts in their rheological characterisation. Soft Matter, 19(11), pp. 2053-2057. (doi: 10.1039/D3SM00077J) (PMID:36866743)

Abstract

Hydrogels have been successfully employed as analogues of the extracellular matrix to study biological processes such as cells' migration, growth, adhesion and differentiation. These are governed by many factors, including the mechanical properties of hydrogels; yet, a one-to-one correlation between the viscoelastic properties of gels and cell fate is still missing from literature. In this work we provide experimental evidence supporting a possible explanation for the persistence of this knowledge gap. In particular, we have employed common tissues' surrogates such as polyacrylamide and agarose gels to elucidate a potential pitfall occurring when performing rheological characterisations of soft-materials. The issue is related to (i) the normal force applied to the samples \textit{prior} to performing the rheological measurements, which may easily drive the outcomes of the investigation outside the materials' linear viscoelastic regime, especially when tests are performed with (ii) geometrical tools having unbefitting dimensions (i.e., too small). We corroborate that biomimetic hydrogels can show either compressional stress softening or stiffening, and we provide a simple solution to quench these undesired phenomena, which would likely lead to potentially misleading conclusions if they were not mitigated by a good practice in performing rheological measurements, as elucidated in this work.

• Item Type: Articles
• Additional Information: M.T. acknowledges support via EPSRC grant “Experiencing the micro-world - a cell’s perspective” (EP/R035067/1 – EP/R035563/1 – EP/R035156/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Tassieri, Dr Manlio and Ferraro, Rosalia
• Authors: Ferraro, R., Guido, S., Caserta, S., and Tassieri, M.
• College/School: College of Science and Engineering > School of Engineering > Biomedical Engineering
• Journal Name: Soft Matter
• Publisher: Royal Society of Chemistry
• ISSN: 1744-683X
• ISSN (Online): 1744-6848
• Published Online: 27 February 2023
• Copyright Holders: Copyright © 2023 The Royal Society of Chemistry
• First Published: First published in Soft Matter 19(11): 2053-2057
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
301441		Experiencing the micro-world - a cell's perspective	Manlio Tassieri	Engineering and Physical Sciences Research Council (EPSRC)	EP/R035067/1	ENG - Biomedical Engineering