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Open AccessArticle

Bioinspired Histidine–Zn2+ Coordination for Tuning the Mechanical Properties of Self-Healing Coiled Coil Cross-Linked Hydrogels

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Mechano(bio)chemistry, Max Planck Institute of Colloids and Interfaces, Science Park Potsdam-Golm, 14424 Potsdam, Germany
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Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Potsdam-Golm, 14424 Potsdam, Germany
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Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC H3A 0B8, Canada
*
Authors to whom correspondence should be addressed.
Biomimetics 2019, 4(1), 25; https://doi.org/10.3390/biomimetics4010025
Received: 2 February 2019 / Revised: 6 March 2019 / Accepted: 6 March 2019 / Published: 18 March 2019
(This article belongs to the Special Issue Biogenic and Bioinspired Self-Healing Materials)
Natural biopolymeric materials often possess properties superior to their individual components. In mussel byssus, reversible histidine (His)–metal coordination is a key feature, which mediates higher-order self-assembly as well as self-healing. The byssus structure, thus, serves as an excellent natural blueprint for the development of self-healing biomimetic materials with reversibly tunable mechanical properties. Inspired by byssal threads, we bioengineered His–metal coordination sites into a heterodimeric coiled coil (CC). These CC-forming peptides serve as a noncovalent cross-link for poly(ethylene glycol)-based hydrogels and participate in the formation of higher-order assemblies via intermolecular His–metal coordination as a second cross-linking mode. Raman and circular dichroism spectroscopy revealed the presence of α-helical, Zn2+ cross-linked aggregates. Using rheology, we demonstrate that the hydrogel is self-healing and that the addition of Zn2+ reversibly switches the hydrogel properties from viscoelastic to elastic. Importantly, using different Zn2+:His ratios allows for tuning the hydrogel relaxation time over nearly three orders of magnitude. This tunability is attributed to the progressive transformation of single CC cross-links into Zn2+ cross-linked aggregates; a process that is fully reversible upon addition of the metal chelator ethylenediaminetetraacetic acid. These findings reveal that His–metal coordination can be used as a versatile cross-linking mechanism for tuning the viscoelastic properties of biomimetic hydrogels. View Full-Text
Keywords: coiled coil; histidine–metal coordination; hydrogel; self-healing; rheology coiled coil; histidine–metal coordination; hydrogel; self-healing; rheology
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MDPI and ACS Style

Tunn, I.; Harrington, M.J.; Blank, K.G. Bioinspired Histidine–Zn2+ Coordination for Tuning the Mechanical Properties of Self-Healing Coiled Coil Cross-Linked Hydrogels. Biomimetics 2019, 4, 25.

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