title: Silk Hydrogels of Tunable Structure and Viscoelastic Properties Using Different Chronological Orders of Genipin and Physical Cross-Linking.
abstract: Catering the hydrogel manufacturing process toward defined viscoelastic properties for intended biomedical use is important to hydrogel scaffolding function and cell differentiation. Silk fibroin hydrogels may undergo "physical" cross-linking through β-sheet crystallization during high pressure carbon dioxide treatment, or covalent "chemical" cross-linking by genipin. We demonstrate here that time-dependent mechanical properties are tunable in silk fibroin hydrogels by altering the chronological order of genipin cross-linking with β-sheet formation. Genipin cross-linking before β-sheet formation affects gelation mechanics through increased molecular weight, affecting gel morphology, and decreasing stiffness response. Alternately, genipin cross-linking after gelation anchored amorphous regions of the protein chain, and increasing stiffness. These differences are highlighted and validated through large amplitude oscillatory strain near physiologic levels, after incorporation of material characterization at molecular and micron length scales.
authors.affiliation: †Department of Industrial Engineering and BIOtech Research Centre, University of Trento, Via Sommarive 9, 38123 Trento, Italy.|‡Department of Mechanical Engineering, University of Colorado, 1111 Engineering Drive, 427 UCB, Boulder, Colorado 80309, United States.
authors.forename: Winston H
authors.initials: WH
authors.lastname: Elliott
authors.affiliation: †Department of Industrial Engineering and BIOtech Research Centre, University of Trento, Via Sommarive 9, 38123 Trento, Italy.|§European Institute of Excellence on Tissue Engineering and Regenerative Medicine, and INSTM Trento Research Unit, 38123 Trento, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Bonani
authors.affiliation: †Department of Industrial Engineering and BIOtech Research Centre, University of Trento, Via Sommarive 9, 38123 Trento, Italy.|§European Institute of Excellence on Tissue Engineering and Regenerative Medicine, and INSTM Trento Research Unit, 38123 Trento, Italy.
authors.forename: Devid
authors.initials: D
authors.lastname: Maniglio
authors.affiliation: †Department of Industrial Engineering and BIOtech Research Centre, University of Trento, Via Sommarive 9, 38123 Trento, Italy.|§European Institute of Excellence on Tissue Engineering and Regenerative Medicine, and INSTM Trento Research Unit, 38123 Trento, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Motta
authors.affiliation: ‡Department of Mechanical Engineering, University of Colorado, 1111 Engineering Drive, 427 UCB, Boulder, Colorado 80309, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Tan
authors.affiliation: †Department of Industrial Engineering and BIOtech Research Centre, University of Trento, Via Sommarive 9, 38123 Trento, Italy.|§European Institute of Excellence on Tissue Engineering and Regenerative Medicine, and INSTM Trento Research Unit, 38123 Trento, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Migliaresi
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D060846:Cell Engineering; D003432:Cross-Linking Reagents / Q000737:chemistry; D005349:Fibroins / Q000737:chemistry*; D006801:Humans; D020100:Hydrogels / Q000737:chemistry* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D039823:Iridoids / Q000737:chemistry*; D017433:Protein Structure, Secondary; D047011:Silk / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D020100:Hydrogels; D039823:Iridoids; D047011:Silk; D002245:Carbon Dioxide; D005349:Fibroins; C007834:genipin
keywords: genipin; high pressure carbon dioxide; large amplitude oscillatory strain; porous hydrogel; silk fibroin