Nanomechanical 3D Depth Profiling of Collagen Fibrils in Native Tendon

In this paper, atomic force microscopy was used to investigate the nanomechanical morphology of individual collagen fibrils in connective tissue and to determine the 3D depth profiles of native (unfixed), hydrated Achilles tendons of sheep and chicken. The profiles were derived by measuring 2D arrays of force-distance and amplitude-phase-distance curves at a high spatial sampling rate using the NanoWizard II AFM (Bruker). The resulting data shows a depth-resolution down to 0.1 nm and a lateral resolution down to 10 nm.

All AFM measurements were performed at 83% relative humidity using a home-built humidifier to retain the tissue’s native water content and nanomechanical properties. The measurements show a diverse distribution of nanomechanical properties among the collagen fibrils and the interfibrillar contacts within the tendon, which indicate that the fibrils are organized in bundles. In addition, the surface of the hydrated tendon was found to be covered by a 5-10 nm thick layer of a fluid-like interfibrillar matrix.

       _{KEY TERMS:}

• Biopolymers, Collagen fibrils, Connective tissue, Nanofibers, Tendon structure, Three-dimensional imaging