Mechanical Properties of Native and Cross-linked Type I Collagen Fibrils

• Published in: Biophysical journal 2008-03, Vol.94 (6), p.2204-2211
• Main Authors: Yang, Lanti, van der Werf, Kees O., Fitié, Carel F.C., Bennink, Martin L., Dijkstra, Pieter J., Feijen, Jan
• Format: Article
• Language: English
• Subjects: Animals; Anisotropy; Bending; Bending modulus; Biochemistry; Biophysics - methods; Cattle; Collagen - chemistry; Collagen Type I - chemistry; Collagens; Cross-Linking Reagents - chemistry; Crosslinking; Equipment Design; Extracellular Matrix - metabolism; Fibers; Fibrillar Collagens - chemistry; Mathematical models; Mechanical properties; Microscopy; Microscopy, Atomic Force; Models, Statistical; Pressure; Proteins; Saline; Shear modulus; Stress, Mechanical; Temperature
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1529/biophysj.107.111013

Micromechanical bending experiments using atomic force microscopy were performed to study the mechanical properties of native and carbodiimide-cross-linked single collagen fibrils. Fibrils obtained from a suspension of insoluble collagen type I isolated from bovine Achilles tendon were deposited on a glass substrate containing microchannels. Force-displacement curves recorded at multiple positions along the collagen fibril were used to assess the bending modulus. By fitting the slope of the force-displacement curves recorded at ambient conditions to a model describing the bending of a rod, bending moduli ranging from 1.0 GPa to 3.9 GPa were determined. From a model for anisotropic materials, the shear modulus of the fibril is calculated to be 33 ± 2 MPa at ambient conditions. When fibrils are immersed in phosphate-buffered saline, their bending and shear modulus decrease to 0.07–0.17 GPa and 2.9 ± 0.3 MPa, respectively. The two orders of magnitude lower shear modulus compared with the Young's modulus confirms the mechanical anisotropy of the collagen single fibrils. Cross-linking the collagen fibrils with a water-soluble carbodiimide did not significantly affect the bending modulus. The shear modulus of these fibrils, however, changed to 74 ± 7 MPa at ambient conditions and to 3.4 ± 0.2 MPa in phosphate-buffered saline.