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pH-Based Regulation of Hydrogel Mechanical Properties Through Mussel-Inspired Chemistry and Processing

Authors

  • Devin G. Barrett,

    1. Biomedical Engineering Department, Chemistry of Life Processes Institute, Institute for Bionanotechnology in Medicine, Northwestern University, Evanston, IL 60208, USA
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  • Dominic E. Fullenkamp,

    1. Biomedical Engineering Department, Chemistry of Life Processes Institute, Northwestern University, Evanston, IL 60208, USA
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  • Lihong He,

    1. Biomedical Engineering Department, Chemistry of Life Processes Institute, Northwestern University, Evanston, IL 60208, USA
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  • Niels Holten-Andersen,

    1. Chemistry Department, Institute for Biophysical Dynamics, James Franck Institute, University of Chicago, Chicago, IL 60637, USA
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  • Ka Yee C. Lee,

    1. Chemistry Department, Institute for Biophysical Dynamics, James Franck Institute, University of Chicago, Chicago, IL 60637, USA
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  • Phillip B. Messersmith

    Corresponding author
    1. Biomedical Engineering Department, Materials Science and Engineering Department, Chemical and Biological Engineering Department, Chemistry of Life Processes Institute, Institute for Bionanotechnology in Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL 60208, USA
    • Biomedical Engineering Department, Materials Science and Engineering Department, Chemical and Biological Engineering Department, Chemistry of Life Processes Institute, Institute for Bionanotechnology in Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL 60208, USA.
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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 is poorly understood. Herein, it is described 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. These 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.

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