title: pH-Based Regulation of Hydrogel Mechanical Properties Through Mussel-Inspired Chemistry and Processing.
abstract: The mechanical holdfast of the mussel, the byssus, is processed at acidic pH yet functions at alkaline pH. Byssi are enriched in Fe3+and catechol-containing proteins, species with chemical interactions that vary widely over the pH range of byssal processing. Currently, the link between pH, Fe3+-catechol reactions, and mechanical function are poorly understood. Herein, we describe how pH influences the mechanical performance of materials formed by reacting synthetic catechol polymers with Fe3+. Processing Fe3+-catechol polymer materials through a mussel-mimetic acidic-to-alkaline pH change leads to mechanically tough materials based on a covalent network fortified by sacrificial Fe3+-catechol coordination bonds. Our findings offer the first direct evidence of Fe3+-induced covalent cross-linking of catechol polymers, reveal additional insight into the pH dependence and mechanical role of Fe3+- catechol interactions in mussel byssi, and illustrate the wide range of physical properties accessible in synthetic materials through mimicry of mussel protein chemistry and processing.
authors.affiliation: Biomedical Engineering Department Chemistry of Life Processes Institute Institute for Bionanotechnology in Medicine Northwestern University Evanston, IL 60208, USA.
authors.forename: Devin G
authors.initials: DG
authors.lastname: Barrett
authors.forename: Dominic E
authors.initials: DE
authors.lastname: Fullenkamp
authors.forename: Lihong
authors.initials: L
authors.lastname: He
authors.forename: Niels
authors.initials: N
authors.lastname: Holten-Andersen
authors.forename: Ka Yee C
authors.initials: KY
authors.lastname: Lee
authors.forename: Phillip B
authors.initials: PB
authors.lastname: Messersmith
keywords: Biomimetics; Hydrogels; Polymeric Materials; Structure-Property Relationships