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As tough as leather: Macro to nano scale perspectives of collagen stability (#48)
K. L. Goh1
1 Newcastle University in Singapore, Newcastle Research & Innovation Institute, Singapore, Singapore
Leather is a fairly durable and flexible material created by tanning animal rawhides and can be found in many household and personal products. However, ensuring that the product endures attack from the environmental elements that contribute to its wear and tear is the key concern of the general consumer. Animal rawhides are soft collagenous connective tissues. The most important function of collagen is a mechanical one—to withstand loads acting on the leather material. The purpose of this paper is to show how findings from recent studies on the mechanics of collagen in connective tissues lend to the goal of structural biologists to establish a complete understanding of the functional significance of collagen in connective tissues. In particular, 28 different types of collagen have been identified—about 90% being type 1 collagen—in the human body. Most types of collagen participate in higher-order assemblies such as networks, filaments, microfibrils, fibrils, fibres/fascicles. These assemblies collectively form a hierarchical architecture in the tissue from the molecular level to the macroscopic level. A complete understanding the functional significance of collagen in connective tissues could direct the development of new technology, e.g. leather design and production. In this paper, I shall discuss findings related to the higher-order assemblies. The conventional understanding of the collagenous fibre-like structures—embedded in a hydrated ground substance—in connective tissue finds an analogy to engineering fibres reinforcing composite materials (Fig. 1) such as carbon fibre reinforced polymer composites. The macroscopic stress-strain response of the connective tissue to external loads acting on it is consistent with fibre composite behaviour (Fig. 1). A structure-mechanical framework, underpinning the hierarchical architecture of the connective tissue, is proposed to explain this mechanical response of the tissue. By integrating models specific to the different levels of the tissue to enable better understanding of the macroscopic nature of the tissue, the framework serves as a representation of reality for guiding further research, especially for the purpose of exploring hypotheses and revealing properties for which only sparse (or no observational data) is available. This paper ends with a discussion on the prospect and challenges for future studies on collagen in connective tissues.
A fresh look at the degree of collagen fibril alignment in tissue
Rethinking the mechanics of cross-linking between fibrils
Interfibrillar mechanics is governed by plastic stress transfer
Influence of fibril diameter on interfibrillar stress transfer
Keywords: connective tissue, biomechanics, multiscale analysis, fibre/matrix interactions, stress transfer mechanisms