Networks of biopolymers can be found throughout the human body, both in the intracellular cytoskeleton, such as actin and intermediate filaments, and in the extracellular matrix, such as collagen and fibrin. These biopolymers all have in common that they can assemble into semi flexible bundles or fibers, which then form a porous network. This morphology gives these biopolymer networks unique mechanical properties, known as strain stiffening; their stiffness increases when they are deformed. In Nijmegen, we developed a thermoresponsive hydrogel based on synthetic helical polyisocyanides (PICs), which forms a gel upon heating and becomes liquid upon cooling down. [1] The thermoreversible gelation is the result of polymer bundle formation, driven by hydrophobic interactions between the polymer chains. This synthetic hydrogel uniquely mimics the morphology and strain stiffening response of biopolymer gels and its stiffness can be tuned over several orders of magnitude. [2, 3] Our goal is to control both the mechanical response and the bundled structure of the PIC gels, in order to use it as a fully tuneable and synthetic extracellular matrix. We use rheology to study the mechanics, and small angle X-ray scattering (SAXS) to study the structure of these biomimetic hydrogels. It was found that both the mechanics and the structure of the gel can be tuned over a broad range using simple variables such as polymer concentration, polymer length, temperature and ion concentration. Moreover, we managed to combine rheology and SAXS, which allows us to study the structure of the PIC hydrogels under deformation. This combination of two techniques provides fundamental insights in the structural mechanism of the strain stiffening response of semi flexible (bio)polymer networks. [1] Kouwer, P. H. J.; Koepf, M.; Le Sage, V. A. A.; Jaspers, M.; van Buul, A. M.; Eksteen-Akeroyd, Z. H.; Woltinge, T.; Schwartz, E.; Kitto, H. J.; Hoogenboom, R.; Picken, S. J.; Nolte, R. J. M.; Mendes, E.; Rowan, A. E. Nature 2013, 493, 651, doi:0.1038/nature11839 [2] Jaspers, M.; Dennison, M.; Mabesoone, M. F. J.; MacKintosh, F. C.; Rowan, A. E.; Kouwer, P. H. J. Nat. Commun. 2014, 5, 5808, doi:10.1038/ncomms6808 [3] Jaspers, M.; Rowan, A. E.; Kouwer, P. H. J. Adv. Funct. Mater. 2015, doi:10.1002/adfm.201502241

Mechanics and structure of strain-stiffening biomimetic hydrogels

251st National Meeting (2016)

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