Mimicking Biological Phenol Reaction Cascades to Confer Mechanical Function

Authors

  • L.-Q. Wu,

    1. Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, MD 20742, USA
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  • M. K. McDermott,

    1. Division of Chemistry and Materials Science, Office of Science and Engineering Laboratories, Food and Drug Administration, 9200 Corporate Blvd., HFZ-150, Rockville, MD 20850, USA
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  • C. Zhu,

    1. Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, MD 20742, USA
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  • R. Ghodssi,

    1. Department of Electrical and Computer Engineering, University of Maryland at College Park, College Park, MD 20742, USA
    2. The Institute for Systems Research, University of Maryland at College Park, College Park, MD 20742, USA
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  • G. F. Payne

    1. Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, MD 20742, USA
    2. Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
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  • Financial support was provided by the National Science Foundation (BES-0114790 and DMI-0321657).

Abstract

Phenol reaction cascades are commonly used in nature to create crosslinked materials that perform mechanical functions. These processes are mimicked by electrochemically initiating a reaction cascade to examine if the mechanical properties of a biopolymer film can be predictably altered. Specifically, thin films (≈ 30–45 μm) of the polysaccharide chitosan are cast onto gold-coated silicon wafers, the chitosan-coated wafers are immersed in catechol-containing solutions, and the phenol is anodically oxidized. The product of this oxidation is highly reactive and undergoes reaction with chitosan chains adjacent to the anode. After reaction, the flexible chitosan film can be peeled from the wafer. Chemical and physical evidence support the conclusion that electrochemically initiated reactions crosslink chitosan. When gold is patterned onto the wafer, the electrochemical crosslinking reactions are spatially localized and impart anisotropic mechanical properties to the chitosan film. Further, deswelling of chitosan films can reversibly transduce environmental stimuli into contractile forces. Films patterned to have spatial variations in crosslinking respond to such environmental stimuli by undergoing reversible changes in shape. These results suggest the potential to enlist electrochemically initiated reaction cascades to engineer chitosan films for actuator functions.

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