In situ multi-level analysis of viscoelastic deformation mechanisms in tendon collagen

Gupta, Himadri S.; Seto, Jong; Krauß, Stefanie; Boesecke, Peter; Screen, Hazel R. C.

doi:10.1016/j.jsb.2009.10.002

Cited by 168 publications

(165 citation statements)

References 51 publications

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“…During ramp-to-failure tests, the SAXS frames were collected with an acquisition time of 200 ms concurrently during mechanical testing with the Pilatus detector being triggered by the testing apparatus software via TTL pulses. Conversely, during stress relaxation experiments the frames were acquired at exponentially increasing time intervals subsequent tissue strain increments of De T = 0.6 % L 0 (up to 3% L 0 ) This exponential curve matched previous published collagen fibril relaxation by Gupta [56] and allowed a most optimal acquisition of data where collagen deformation occurred. A shutter closing between frames reduced the X-ray dose at the sample.…”

Section: Mechanical Testing Coupled With Small-angle X-ray Scatteringmentioning

confidence: 78%

“…The tensile tester was a modification of an available micro-compression device [55], which was designed to fit on the stage of the coherent small-angle X-ray scattering (cSAXS) beamline at Swiss Light Source (Paul Scherrer Institute, Switzerland). During all experiments two 4 μm Ultralene films (X-ray semitransparent material) were placed on two sides of each tendon held together by a drop of PBS to maintain tissue hydration [56].…”

Section: Mechanical Testing Coupled With Small-angle X-ray Scatteringmentioning

confidence: 99%

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Advanced glycation end-products: Mechanics of aged collagen from molecule to tissue

et al. 2017

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Concurrent with a progressive loss of regenerative capacity, connective tissue aging is characterized by a progressive accumulation of Advanced Glycation End-products (AGEs). Besides being part of the typical aging process, type II diabetics are particularly affected by AGE accumulation due to abnormally high levels of systemic glucose that increases the glycation rate of long-lived proteins such as collagen. Although AGEs are associated with a wide range of clinical disorders, the mechanisms by which AGEs contribute to connective tissue disease in aging and diabetes are still poorly understood. The present study harnesses advanced multiscale imaging techniques to characterize a widely employed in vitro model of ribose induced collagen aging and further benchmarks these data against experiments on native human tissues from donors of different age. These efforts yield unprecedented insight into the mechanical changes in collagen tissues across hierarchical scales from molecular, to fiber, to tissue-levels. We observed a linear increase in molecular spacing (from 1.45 nm to 1.5 nm) and a decrease in the D-period length (from 67.5 nm to 67.1 nm) in aged tissues, both using the ribose model of in vitro glycation and in native human probes. Multiscale mechanical analysis of in vitro glycated tendons strongly suggests that AGEs reduce tissue viscoelasticity by severely limiting fiber-fiber and fibril-fibril sliding. This study lays an important foundation for interpreting the functional and biological effects of AGEs in collagen connective tissues, by exploiting experimental models of AGEs crosslinking and benchmarking them for the first time against endogenous AGEs in native tissue.

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Section: Mechanical Testing Coupled With Small-angle X-ray Scatteringmentioning

confidence: 78%

Section: Mechanical Testing Coupled With Small-angle X-ray Scatteringmentioning

confidence: 99%

Advanced glycation end-products: Mechanics of aged collagen from molecule to tissue

et al. 2017

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“…Cross-linking of molecules, fibrils and fibers is a critical feature in numerous connective tissues such as bone, tendon, cartilage or blood vessels [1][2][3]. In these tissues, the mechanical strength is primarily provided by strong and elastic molecules such as collagen and elastin [4,5], which arrange into highly organized hierarchical structures [1][2][3]6] where the formation of intermolecular covalent cross-links is important in enhancing the mechanical stability of the resulting tissues.…”

Section: Introductionmentioning

confidence: 99%

“…In these tissues, the mechanical strength is primarily provided by strong and elastic molecules such as collagen and elastin [4,5], which arrange into highly organized hierarchical structures [1][2][3]6] where the formation of intermolecular covalent cross-links is important in enhancing the mechanical stability of the resulting tissues. However, when the cross-link density increases, as found in elderly individuals, effects such as skin wrinkling, cartilage impairment or bone embrittlement as in osteoporosis and diabetes can occur [7,8].…”

Section: Introductionmentioning

confidence: 99%

Molecular structure, mechanical behavior and failure mechanism of the C-terminal cross-link domain in type I collagen

Uzel

Buehler

2011

Journal of the Mechanical Behavior of Biomedical Materials

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ABSTRACT:Collagen is a key constituent in structural materials found in biology, including bone, tendon, skin and blood vessels. Here we report a first molecular level model of an entire overlap region of a C-terminal cross-linked type I collagen assembly and carry out a nanomechanical characterization based on large-scale molecular dynamics simulation in explicit water solvent. Our results show that the deformation mechanism and strength of the structure is greatly affected by the presence of the cross-link, and by the specific loading condition of how the stretching is applied. We find that the presence of a cross-link results in greater strength during deformation as complete intermolecular slip is prevented, and thereby particularly affects larger deformation levels. Conversely, the lack of a cross-link results in the onset of intermolecular sliding during deformation and as a result an overall weaker structure. Through a detailed analysis of the distribution of deformation by calculating the molecular strain we show that the location of largest strains does not occur around the covalent bonding region, but is found in regions further away from this location. The insight developed from understanding collagenous materials from a fundamental molecular level upwards could play a role in advancing our understanding of physiological and disease states of connective tissues, and also enable the development of new scaffolding material for applications in regenerative medicine and biologically inspired materials. Keywords

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“…These fibers consist of fibrils, which are connected by proteoglycan (PG) bridges. The time-dependent properties of soft tissues appear to be mainly caused by proteoglycans [3]. This contribution presents a modeling approach where damage in the PG bridges arises due to the failure of the covalent bonds between two proteoglycans.…”

mentioning

confidence: 99%

Failure of adhesive bonds between proteoglycans causes viscoelasticity of soft tissues

Hillgärtner

Linka

Itskov

2016

Proc Appl Math and Mech

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Soft tissues can be considered as a composite material where a matrix (ground substance) is reinforced by collagen fibers. These fibers consist of fibrils, which are connected by proteoglycan (PG) bridges. The time-dependent properties of soft tissues appear to be mainly caused by proteoglycans [3]. This contribution presents a modeling approach where damage in the PG bridges arises due to the failure of the covalent bonds between two proteoglycans. The breakage of covalent bonds is reversible over time and incorporated using a healing formulation. A high PG density supports interfibrillar sliding and hence leads to a lower fibril stretch [8]. Accordingly, the damage propagation in PG bridges leads to a higher stretch in the fibrils and therefore to a stiffer material response. The strain energy of the fibrils is based on the response of single tropocollagen molecules and takes both, an entropic and an energetic regime into account [5]. Finally, the model is compared against experimental data available in the literature.

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In situ multi-level analysis of viscoelastic deformation mechanisms in tendon collagen

Cited by 168 publications

References 51 publications

Advanced glycation end-products: Mechanics of aged collagen from molecule to tissue

Advanced glycation end-products: Mechanics of aged collagen from molecule to tissue

Molecular structure, mechanical behavior and failure mechanism of the C-terminal cross-link domain in type I collagen

Failure of adhesive bonds between proteoglycans causes viscoelasticity of soft tissues

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