Assembly of type I collagen: fusion of fibril subunits and the influence of fibril diameter on mechanical properties.
Structural stability of the extracellular matrix is primarily a consequence of fibrillar collagen and the extent of cross-linking. The relationship between collagen self-assembly, consequent fibrillar shape and mechanical properties remains unclear. Our laboratory developed a model system for the preparation of self-assembled type I collagen fibers with fibrillar substructure mimicking the hierarchical structures of tendon. The present study evaluates the effects of pH and temperature during self-assembly on fibrillar structure, and relates the structural effects of these treatments on the uniaxial tensile mechanical properties of self-assembled collagen fibers. Results of the analysis of fibril diameter distributions and mechanical properties of the fibers formed under the different incubation conditions indicate that fibril diameters grow via the lateral fusion of discrete approximately 4 nm subunits, and that fibril diameter correlates positively with the low strain modulus. Fibril diameter did not correlate with either the ultimate tensile strength or the high strain elastic modulus, which suggests that lateral aggregation and consequently fibril diameter influences mechanical properties during small strain mechanical deformation. We hypothesize that self-assembly is mediated by the formation of fibrillar subunits that laterally and linearly fuse resulting in fibrillar growth. Lateral fusion appears important in generating resistance to deformation at low strain, while linear fusion leading to longer fibrils appears important in the ultimate mechanical properties at high strain.
Christiansen
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DL
Division of Biomaterials, Department of Pathology and Laboratory Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA.
Huang
E K
EK
Silver
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FH
D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000737:chemistry / Q000502:physiology; D005998:Glycine; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D051381:Rats; D012965:Sodium Chloride; D013696:Temperature; D013710:Tendons / Q000737:chemistry / Q000502:physiology
D046911:Macromolecular Substances; D012965:Sodium Chloride; D003094:Collagen; D005998:Glycine