title: Cartilage-like electrostatic stiffening of responsive cryogel scaffolds.
abstract: Cartilage is a structural tissue with unique mechanical properties deriving from its electrically-charged porous structure. Traditional three-dimensional environments for the culture of cells fail to display the complex physical response displayed by the natural tissue. In this work, the reproduction of the charged environment found in cartilage is achieved using polyelectrolyte hydrogels based on polyvinyl alcohol and polyacrylic acid. The mechanical response and morphology of microporous physically-crosslinked cryogels are compared to those of heat-treated chemical gels made from the same polymers, as a result of pH-dependent swelling. In contrast to the heat-treated chemically-crosslinked gels, the elastic modulus of the physical cryogels was found to increase with charge activation and swelling, explained by the occurrence of electrostatic stiffening of the polymer chains at large charge densities. At the same time, the permeability of both materials to fluid flow was impaired by the presence of electric charges. This cartilage-like mechanical behavior displayed by responsive cryogels can be reproduced in other polyelectrolyte hydrogel systems to fabricate biomimetic cellular scaffolds for the repair of the tissue.
authors.affiliation: Nanoscience Centre, Department of Engineering, University of Cambridge, Cambridge CB3 0FF, UK.|Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK.
authors.forename: G S
authors.initials: GS
authors.lastname: Offeddu
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
authors.forename: I
authors.initials: I
authors.lastname: Mela
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
authors.forename: P
authors.initials: P
authors.lastname: Jeggle
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Henderson
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK.
authors.forename: S K
authors.initials: SK
authors.lastname: Smoukov
authors.affiliation: Nanoscience Centre, Department of Engineering, University of Cambridge, Cambridge CB3 0FF, UK.
authors.forename: M L
authors.initials: ML
authors.lastname: Oyen
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002358:Cartilage, Articular / Q000502:physiology*; D019245:Compressive Strength; D059985:Cryogels / Q000737:chemistry*; D055119:Elastic Modulus; D020100:Hydrogels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D010539:Permeability; D000071228:Polyelectrolytes / Q000737:chemistry; D011142:Polyvinyl Alcohol / Q000737:chemistry; D016062:Porosity; D055672:Static Electricity; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D059985:Cryogels; D020100:Hydrogels; D000071228:Polyelectrolytes; C006903:carbopol 940; D011142:Polyvinyl Alcohol