Chemical Physics Lab
Collagen fibrils

Collagen fibrils

Nanomechanical properties of the most abundant structural protein in vertebrates

  • Maps of the elastic modulus (left) and the energy dissipated between tip and sample (right) of a hydrated, reconstituted collagen fibril. Figure: M. R. Uhlig, R. Magerle, Nanoscale 9, 1244–1256 (2017); © The Royal Society of Chemistry 2017
  • Nanoscale swelling behavior of a reconstituted collagen fibril. MUSIC-mode atomic force microscopy images of the undisturbed surface (a) before swelling, (b) in the hydrated state at 78% relative humidity and (c) after swelling. (d) Height profiles along the fibril backbone. The gap regions of the D-band swell more than the overlap regions. This is direct evidence of a higher content of free water molecules in the gap regions. Figure: E.-C. Spitzner, S. Röper, M. Zerson, A. Bernstein, R. Magerle, ACS Nano 9, 5683–5694 (2015); © 2015 American Chemical Society.
  • Collagen fibrils in a hydrated sheep tendon, imaged using tapping-mode atomic force microscopy.

Collagens are a major component of the connective tissue of vertebrates and provide mechanical strength to tissues. The most abundant type is type I collagen, which forms fibrils 30 to 300 nm in diameter and has a periodic structure with a lattice constant of 67 nm along the fibril axis. The amount and distribution of water, lipids (fats), and molecular bonds between collagen molecules determine and control the mechanical properties of collagen fibrils.

We study the nanoscale mechanical properties of hydrated collagen fibrils using atomic force microscopy and force spectroscopy, whereby the water content of the fibrils can be controlled through the level of humidity. The swelling behavior of the fibrils provides direct information about the local content of free water molecules in the overlap and gap regions of the D-band [1]. Furthermore, we can reconstruct spatial depth profiles of the tip-sample interaction force and thus distinguish the contribution of capillary force and adhesion from the viscoelastic properties of the collagen fibrils [2]. This allows us to study the nanomechanical properties of individual collagen fibrils in natural tendons with a spatial resolution of 10 nm [3]. We have also used atomic force microscopy-based nanotomography to image the spatial arrangement of individual collagen fibrils in bone [4].

[1]  E.-C. Spitzner, S. Röper, M. Zerson, A. Bernstein, R. Magerle, ACS Nano 9, 5683–5694 (2015).
[2]  M. R. Uhlig, R. Magerle, Nanoscale 9, 1244–1256 (2017); free author manuscript: arXiv:1910.00794.
[3]  R. Magerle, M. Dehnert, D. Voigt, A. Bernstein, Analytical Chemistry 92, 8741–8749 (2020).
[4]  S. Röper, Dissertation, TU Chemnitz (2010).  PDF