Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5512372 | International Journal of Biological Macromolecules | 2017 | 31 Pages |
Abstract
We investigate the linear and nonlinear viscoelastic properties as well as the reversibility of strain-stiffening behavior of silk fibroin gels. The gels are prepared from 4.2 w/v% fibroin solution in the presence of butanediol diglycidyl ether and N,N,N',N'-tetramethylethylenediamine (TEMED) as a cross-linker and catalyst, respectively. By changing the concentration of TEMED in the gelation system, fibroin gels exhibiting a storage modulus G' between 10â1-105 Pa and a loss factor tan δ between 10â2 and 10° could be obtained. We observe a strong stiffening (up to 900%) in fibroin gels with increasing strain above 10% deformation, but reversibly if the strain is removed, the gel recovers its initial viscoelastic properties. The strain induced formation of transient intermolecular domains acting as reversible cross-links are responsible for the stiffening behavior of fibroin gels. These additional cross-links formed in the hardened fibroin gels have a temporary nature with lifetimes of the order of seconds. The nonlinear behavior of fibroin gels can be reproduced by a wormlike chain model taking into account the entropic elasticity of fibroin molecules and the strain induced increase in the cross-link density of fibroin gels.
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Authors
Zeynep Oztoprak, Oguz Okay,