title: Silk Fibroin Aqueous-Based Adhesives Inspired by Mussel Adhesive Proteins.
abstract: Silk fibroin from the domesticated silkworm Bombyx mori is a naturally occurring biopolymer with charged hydrophilic terminal regions that end-cap a hydrophobic core consisting of repeating sequences of glycine, alanine, and serine residues. Taking inspiration from mussels that produce proteins rich in L-3,4-dihydroxyphenylalanine (DOPA) to adhere to a variety of organic and inorganic surfaces, the silk fibroin was functionalized with catechol groups. Silk fibroin was selected for its high molecular weight, tunable mechanical and degradation properties, aqueous processability, and wide availability. The synthesis of catechol-functionalized silk fibroin polymers containing varying amounts of hydrophilic polyethylene glycol (PEG, 5000 g/mol) side chains was carried out to balance silk hydrophobicity with PEG hydrophilicity. The efficiency of the catechol functionalization reaction did not vary with PEG conjugation over the range studied, although tuning the amount of PEG conjugated was essential for aqueous solubility. Adhesive bonding and cell compatibility of the resulting materials were investigated, where it was found that incorporating as little as 6 wt % PEG prior to catechol functionalization resulted in complete aqueous solubility of the catechol conjugates and increased adhesive strength compared with silk lacking catechol functionalization. Furthermore, PEG-silk fibroin conjugates maintained their ability to form β-sheet secondary structures, which can be exploited to reduce swelling. Human mesenchymal stem cells (hMSCs) proliferated on the silks, regardless of PEG and catechol conjugation. These materials represent a protein-based approach to catechol-based adhesives, which we envision may find applicability as biodegradable adhesives and sealants.
authors.affiliation: Department of Biomedical Engineering, Tufts University , 4 Colby Street, Medford, Massachusetts 02155, United States.|Department of Chemical and Biomolecular Engineering, University of Connecticut , 191 Auditorium Road, Storrs, Connecticut 06269, United States.|Polymer Program, Institute of Materials Science, University of Connecticut , 97 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Burke
authors.affiliation: Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States.
authors.forename: Dane C
authors.initials: DC
authors.lastname: Roberts
authors.affiliation: Department of Biomedical Engineering, Tufts University , 4 Colby Street, Medford, Massachusetts 02155, United States.
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000138:chemical synthesis*; D049872:Bivalvia; D012831:Bombyx; D002478:Cells, Cultured; D005349:Fibroins / Q000138:chemical synthesis*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D011092:Polyethylene Glycols / Q000737:chemistry; D017433:Protein Structure, Secondary; D011506:Proteins / Q000378:metabolism; D047011:Silk / Q000737:chemistry; D014014:Tissue Adhesives / Q000138:chemical synthesis*
chemical_list: D001672:Biocompatible Materials; D011506:Proteins; D047011:Silk; D014014:Tissue Adhesives; C037403:adhesive protein, mussel; D011092:Polyethylene Glycols; D005349:Fibroins