Abstract
The piezoelectricity of collagen is purported to be linked to many biological processes including bone formation and wound healing. Although the piezoelectricity of tissue-derived collagen has been documented across the length scales, little work has been undertaken to characterise the local electromechanical properties of processed collagen, which is used as a base for tissue-engineering implants. In this work, three chemically distinct treatments used to form structurally and mechanically stable scaffolds— EDC-NHS, genipin and tissue transglutaminase—are investigated for their effect on collagen piezolectricity. Crosslinking with EDC-NHS is noted to produce a distinct self-assembly of the fibres into bundles roughly 300 nm in width regardless of the collagen origin. These fibre bundles also show a localised piezoelectric response, with enhanced vertical piezoelectricity of collagen. Such topographical features are not observed with the other two chemical treatments, although the shear piezoelectric response is significantly enhanced upon crosslinking. These observations are reconciled by a proposed effect of the crosslinking mechanisms on the molecular and nanostructure of collagen. These results highlight the ability to modify the electromechanical properties of collagen using chemical crosslinking methods.
Highlights
As the primary structural protein in mammalian tissues, there has been significant interest in the physical properties of collagen, including its inherent piezoelectricity
It has been suggested that the piezoelectric nature of collagen plays a role in various biological processes including bone formation, resorption[1] and wound healing.[2,3]
All modulus measurements of the collagen films were within the GPa scale
Summary
As the primary structural protein in mammalian tissues, there has been significant interest in the physical properties of collagen, including its inherent piezoelectricity. It has been suggested that the piezoelectric nature of collagen plays a role in various biological processes including bone formation, resorption[1] and wound healing.[2,3] The ubiquity of collagen across various tissues makes collagen a viable base material for tissue engineering applications. In such applications, the collagen-based device is routinely crosslinked to provide the durability and mechanical integrity needed for the intended duration of service. Research on collagen piezoelectricity has burgeoned over the last five decades, the hierarchical structure of collagen has posed a challenge in deciphering the origins of its piezoelectric effect.[4,5,6] The earliest measurements of collagen’s piezoelectric coefficients by Fukada et al describe the ability of collagen to naturally form highly aligned oriented fibres[5] resulting in one of the highest piezoelectric responses (12 pC N−1) observed in ordered natural biopolymers.[7]
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