Poly(vinyl alcohol)–acrylamide hydrogels as load-bearing cartilage substitute

Bodugoz-Senturk, Hatice; Macias, Celia E.; Kung, Jean H.; Muratoglu, Orhun K.

doi:10.1016/j.biomaterials.2008.10.010

Cited by 207 publications

(181 citation statements)

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“…The annealing process enhances the mobility of PVA chains and promotes crystallization. 21,23 This step generates a much higher density of PVA crystallites than the freezethaw method developed by Peppas. 20 The resulting dry gel is translucent, indicative of phase separation ( Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

“…23 Muratoglu and coworkers polymerized acrylamide monomers in the pores of a PVA hydrogel to form uncross-linked chains, and showed that the equilibrium water content of the resulting gels increased with acrylamide content, while the coefficient of friction, tear strength and creep resistance decreased. 21 Here we propose that a hybrid network of a crystalline polymer and a covalently crosslinked hydrophilic polymer may form a hydrogel with robust mechanical properties and good chemical stability: the crystalline polymer can generate a large number of crystallites to serve as physical cross-links that are both stable and reversible; the covalently cross-linked hydrophilic polymer maintain the elasticity of the network during deformation and controls the swelling of the hydrogel. We describe one such hybrid hydrogel that combines extremely high stiffness, strength, and toughness.…”

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confidence: 99%

“…PVA is widely used and has seen extensive development for biomedical applications. 20,21 In 1975, Peppas discovered that a sequence of freeze and thaw cycles could produce PVA hydrogels where crystallites serve as cross-links. 20 Unfortunately, hydrogels synthesized using this method are compliant and brittle.…”

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Stiff, strong, and tough hydrogels with good chemical stability

2014

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Most hydrogels have poor mechanical properties, severely limiting their scope of applications.Here we report on a hybrid hydrogel that combines extremely high stiffness, strength, and toughness, while maintaining physical integrity in electrolyte solutions. The hydrogel consists of a hydrophilic polymer network that is covalently cross-linked and a second polymer network that can crystallize. We show that the crystallites serve as physical cross-links for the second network.The crystallites contribute to the high stiffness and strength of the hydrogel; they unzip and dissipate energy under deformation, and reform due to the incompatibility of the two polymers in the hydrogel. The crystallite-toughened hydrogel can achieve an elastic modulus of 5 MPa, a strength of 2.5 MPa, and a fracture energy of 14,000 Jm -2 . Unlike alginate-based hybrid hydrogels, this hydrogel preserves its mechanical properties in electrolyte solutions and could be considered for further development in a variety of engineering applications. 20 Unfortunately, hydrogels synthesized using this method are compliant and brittle. 22 It is possible to achieve higher stiffness and toughness using a dry-anneal method, but only at the expense of a much lower water content ( Supplementary Fig. S1). 23 Muratoglu and coworkers polymerized acrylamide monomers in the pores of a PVA hydrogel to form uncross-linked chains, and showed that the equilibrium water content of the resulting gels increased with acrylamide content, while the coefficient of friction, tear strength and creep resistance decreased. 21Here we propose that a hybrid network of a crystalline polymer and a covalently crosslinked hydrophilic polymer may form a hydrogel with robust mechanical properties and good chemical stability: the crystalline polymer can generate a large number of crystallites to serve as physical cross-links that are both stable and reversible; the covalently cross-linked hydrophilic polymer maintain the elasticity of the network during deformation and controls the swelling of the hydrogel. We describe one such hybrid hydrogel that combines extremely high stiffness, strength, and toughness. The hydrogel consists of a hydrophilic polyacrylamide (PAAm) polymer network that is covalently cross-linked and a PVA network that forms crystallites. We show that the PVA crystallites result in a high cross-link density, thus producing a gel of remarkable stiffness and strength. The crystallites unzip under deformation, dissipating energy in the process and yielding a hydrogel with exceptional toughness. After deformation, unzipped crystallites recover at room temperature due to the incompatibility of the two polymers in the gel. The 4 crystallite-toughened hydrogel can achieve an elastic modulus of 5 MPa, a strength of 2.5 MPa, and a fracture energy of 14,000 Jm -2 . Moreover, these properties are stable, even in concentrated electrolyte solutions. ResultsWe prepared the hybrid hydrogels in a simple three-step protocol. First, we form a cross- Supplementary Fig. S2); e...

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Section: Resultsmentioning

confidence: 99%

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Stiff, strong, and tough hydrogels with good chemical stability

2014

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“…It has been studied as bone substitute material or bone scaffold coating when mixed with ceramics [14][15][16], a synthetic articular cartilage [17][18][19], artificial pancreas [20], artificial skins [21,22], and drug delivery systems [23], etc. To improve the stability of PVA in body fluids, glutaraldehybe is often used to crosslink PVA [21].…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Porous poly(vinyl alcohol)/sepiolite bone scaffolds: Preparation, structure and mechanical properties

Killeen

Frydrych

Chen

2012

Materials Science and Engineering: C

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Porous poly(vinyl alcohol) (PVA)/sepiolite nanocomposite scaffolds containing 0-10wt.% sepiolite were prepared by freeze-drying and thermally crosslinked with poly(arylic acid).The microstructure of the obtained scaffolds was characterised by scanning electron microscopy and micro computer tomography, which showed a ribbon and ladder like interconnected structure. The incorporation of sepiolite increased the mean pore size and porosity of the PVA scaffold as well as the degree of anisotropy due to its fibrous structure.The tensile strength, modulus and energy at break of the PVA solid material that constructed the scaffold were found to improve with additions of sepiolite by up to 104%, 331% and 22% for 6wt.% clay. Such enhancements were attributed to the strong interactions between the PVA and sepiolite, the good dispersion of sepiolite nanofibres in the matrix and the intrinsic properties of the nanofibres. However, the tensile properties of the PVA scaffold deteriorated in the presence of sepiolite because of the higher porosity, pore size and degree of anisotropy.The PVA/sepiolite nanocomposite scaffold containing 6wt.% sepiolite was characterized by an interconnected structure, a porosity of 89.5% and a mean pore size of 79μm and exhibited a tensile strength of 0.44MPa and modulus of 14.9MPa, which demonstrates potential for this type of materials to be further developed as bone scaffolds.

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“…26 PVA hydrogels can also be physically crosslinked through the formation of crystallites during annealing and dehydration, freeze-thaw cycling, or by phase separation from theta-solutions. 24,[115][116][117] PVA hydrogels have been extensively characterized and compared to articular cartilage in terms of their mechanical, fluid flow, and frictional properties ( Table 2). Values of compressive modulus, shear modulus, tensile modulus, and permeability were similar to articular cartilage.…”

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confidence: 99%