title: Boronate complex formation with Dopa containing mussel adhesive protein retards ph-induced oxidation and enables adhesion to mica.
abstract: The biochemistry of mussel adhesion has inspired the design of surface primers, adhesives, coatings and gels for technological applications. These mussel-inspired systems often focus on incorporating the amino acid 3,4-dihydroxyphenyl-L-alanine (Dopa) or a catecholic analog into a polymer. Unfortunately, effective use of Dopa is compromised by its susceptibility to auto-oxidation at neutral pH. Oxidation can lead to loss of adhesive function and undesired covalent cross-linking. Mussel foot protein 5 (Mfp-5), which contains ∼ 30 mole % Dopa, is a superb adhesive under reducing conditions but becomes nonadhesive after pH-induced oxidation. Here we report that the bidentate complexation of borate by Dopa to form a catecholato-boronate can be exploited to retard oxidation. Although exposure of Mfp-5 to neutral pH typically oxidizes Dopa, resulting in a>95% decrease in adhesion, inclusion of borate retards oxidation at the same pH. Remarkably, this Dopa-boronate complex dissociates upon contact with mica to allow for a reversible Dopa-mediated adhesion. The borate protection strategy allows for Dopa redox stability and maintained adhesive function in an otherwise oxidizing environment.
authors.affiliation: Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, and School of Mechanical Engineering, Southeast University, Nanjing, China; Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Yajing
authors.initials: Y
authors.lastname: Kan
authors.affiliation: Biomolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Eric W
authors.initials: EW
authors.lastname: Danner
authors.affiliation: Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Israelachvili
authors.affiliation: Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, and School of Mechanical Engineering, Southeast University, Nanjing, China.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Biomolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: J Herbert
authors.initials: JH
authors.lastname: Waite
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry; D000818:Animals; D001897:Boronic Acids / Q000737:chemistry*; D004295:Dihydroxyphenylalanine / Q000737:chemistry*; D008974:Mollusca / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*
chemical_list: D000269:Adhesives; D000538:Aluminum Silicates; D001897:Boronic Acids; D011506:Proteins; C037403:adhesive protein, mussel; D004295:Dihydroxyphenylalanine; C011934:mica