title: Diepoxide-triggered conformational transition of silk fibroin: formation of hydrogels.
abstract: Silk fibroin hydrogels with tunable properties could be obtained from aqueous fibroin solutions (4.2 w/v %) in a short period of time. This was achieved by the addition of ethylene glycol diglycidyl ether (EGDE) into the reaction solution. Introduction of EGDE cross-links between the fibroin molecules decreases the mobility of the chains, which triggers the conformational transition from random-coil to β-sheet structure and hence fibroin gelation. Dynamic rheological measurements conducted at 50 °C show the formation of strong to weak hydrogels depending on the pH of the reaction solution. Although EGDE attacks the amino groups of fibroin and forms interstrand cross-links, β-sheets acting as physical cross-links dominate the elasticity of the hydrogels. Mechanical response of low-modulus fibroin hydrogels formed above pH 9.7 is highly nonlinear with strong strain hardening behavior (700%) arising from the alignment of the crystallizable amino acid segments.
authors.affiliation: Istanbul Technical University, Department of Chemistry, Istanbul, Turkey.
authors.forename: Ilknur
authors.initials: I
authors.lastname: Karakutuk
authors.forename: Fatih
authors.initials: F
authors.lastname: Ak
authors.forename: Oguz
authors.initials: O
authors.lastname: Okay
mesh_terms: D000818:Animals; D003432:Cross-Linking Reagents / Q000138:chemical synthesis* / Q000737:chemistry; D004853:Epoxy Resins / Q000737:chemistry*; D005349:Fibroins / Q000737:chemistry*; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry; D020100:Hydrogels / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D012212:Rheology; D047011:Silk / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: D003432:Cross-Linking Reagents; D004853:Epoxy Resins; D005782:Gels; D020100:Hydrogels; D047011:Silk; D012996:Solutions; D014867:Water; C035364:Quetol 651; D005349:Fibroins