Collagen fibrils from physiologically distinct tendons follow unique paths to failure

Abstract

The collagen fibril is a fundamental unit in the mammalian class, providing strength and structure to various tissues. Here, I investigated the mechanical, morphological, and molecular properties of isolated collagen fibrils from two bovine forelimb tendons, which compose an energy storing - positional tendon pair. For each isolated fibril, two strips of glue were used to isolate a segment, which was pulled to rupture with an atomic force microscope. The stress-strain behavior of single fibrils was highly dependent on tendon type. Post-rupture AFM imaging showed that flexor fibrils were robust against plastic damage, while extensor fibrils were susceptible to plastic deformation. Second harmonic generation microscopy was used to investigate molecular organization pre- and post-rupture, and the molecular state was not altered by rupture in flexor fibrils, but was disrupted in extensor fibrils. The work shows that fibrils from distinct tendons follow unique mechanistic paths to failure.