Micromechanical analysis of native and cross-linked collagen type I fibrils supports the existence of microfibrils.
The mechanical properties of individual collagen fibrils of approximately 200 nm in diameter were determined using a slightly adapted AFM system. Single collagen fibrils immersed in PBS buffer were attached between an AFM cantilever and a glass surface to perform tensile tests at different strain rates and stress relaxation measurements. The stress-strain behavior of collagen fibrils immersed in PBS buffer comprises a toe region up to a stress of 5 MPa, followed by the heel and linear region at higher stresses. Hysteresis and strain-rate dependent stress-strain behavior of collagen fibrils were observed, which suggest that single collagen fibrils have viscoelastic properties. The stress relaxation process of individual collagen fibrils could be best fitted using a two-term Prony series. Furthermore, the influence of different cross-linking agents on the mechanical properties of single collagen fibrils was investigated. Based on these results, we propose that sliding of microfibrils with respect to each other plays a role in the viscoelastic behavior of collagen fibrils in addition to the sliding of collagen molecules with respect to each other. Our finding provides a better insight into the relationship between the structure and mechanical properties of collagen and the micro-mechanical behavior of tissues.
Polymer Chemistry and Biomaterials, Faculty of Science & Technology and Institute for Biomedical Technology and Technical Medicine (MIRA), University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
L
L
Yang
K O
KO
van der Werf
P J
PJ
Dijkstra
J
J
Feijen
M L
ML
Bennink
D000818:Animals; D002021:Buffers; D002417:Cattle; D024042:Collagen Type I / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004548:Elasticity; D005898:Glass / Q000737:chemistry; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014783:Viscosity
D002021:Buffers; D024042:Collagen Type I; D003432:Cross-Linking Reagents