3D X-ray reveals secrets from inside bones

Date:
June 15, 2020
Source:
Aarhus University
Summary:
Researchers have uncovered a previously unknown substructure in
bone tissue using a new X-ray technique to produce 3D images
of the internal structure of bones. The discovery potentially
questions fundamentally a number of the models of bone tissue
and the mechanical properties of bones that, among other things,
is used to describe the process of bone formation.



FULL STORY ==========================================================================
An international research team has used new X-ray techniques to describe
how the architecture of healthy human bones is built up. The team has
uncovered a hitherto unknown structure in healthy bones.


==========================================================================
The human bone is a wonderful and fantastic biological material. Bone
tissue is highly specialised, with a structure optimised for specific
functions in the body. Healthy bones are strong, they have a high carrying capacity, and they are hard to break.

The internal structure of bones is of great international interest to researchers, and a better understanding of the fundamental biomaterial structures would make it possible to prevent various bone diseases. It
could also facilitate the development of completely new materials, with unprecedented properties. However, the structure of the bones is simply
too complex for us to be able to come close to imitating it.

An international team of researchers from Aarhus University i Denmark,
the European Synchotron in France (ESRF), the Swedish Chalmers University
and the Paul Scherrer Institute in Switzerland have now uncovered a
previously unknown substructure in bone tissue by means of a new X-ray technique. The discovery and the technique open up for new approaches to
the study of the underlying architecture of bone tissue, and to create
a better understanding of biomaterials.

The study is presented in the scientific magazine, Science Advances.

3D image of the crystals in bones If you cut into a bone, we know that
the inner architecture of healthy bone tissue is constructed of basically
two types of tissue: the so-called collagen fibrillations, which are
primarily made up of protein. They comprise the bearing capacity of the mechanical properties of bone, with a microscopic, thread-like structure
woven together with nanocrystals of minerals containing calcium.



========================================================================== Together, the two tissue types constitute a twisted hierarchical structure
with the ability of the fibrillations to withstand stretching forces
and bending, and the hardness and resilience of nanocrystals. It is this twisted structure that provides bones with their mechanical properties,
and which researchers have been trying to understand for many years.

"The challenge until now has been that we have no method to demonstrate
the orientation of the nanocrystals in the bone tissue," explains
Associate Professor Henrik Birkedal from iNANO and the Department of
Chemistry at Aarhus University.

The international team has succeeded in finding the solution by improving
the X-ray technique known as tensor tomography, and by creating an
accurate 3D map of the crystals in the tissue.

"In recent years, significant technological and scientific progress has
made this new method possible. By means of more powerful synchrotron
radiation, it is possible to improve the method, and to challenge the
previous assumption about bone tissue," explains Manfred Burghammer
from the research facility ID13 at the ESRF, who has been the research
director of the project together with Henrik Birkedal.

The improved method makes it possible to see how the nanocrystals are
actually located in the structure. This has already revealed a disparity
with previous knowledge about bones that has been built up through many
years of research.

The bone structure is not uniformly structured as previously assumed,
because there are deviations in the orientation of the nanocrystals.



========================================================================== "Frankly, we were a little shocked to find the deviation from the
models," says Henrik Birkedal. "It's been a really cross-disciplinary, international collaboration with participants from physics, chemistry and health sciences, and we were all pleasantly surprised by the discovery."
New knowledge with unknown significance The new 3D images surprised the research group, because they conflict with fundamental theories that
bones are built up in a predominantly uniform hierarchical structure.

"Admittedly, it's too early to give an unambiguous explanation of what
hides behind the deviation we have demonstrated, but it has given science
a new method of looking into the underlying structure of bones," says
Tilman Gru"newald from the ESRF.

The discovery potentially questions fundamentally a number of the models
of bone tissue and the mechanical properties of bones that, among other
things, have been used to describe the process of bone formation.

"Bones and other biomaterials, like sea shells, have a mechanical and structural characteristic that is closely linked to their structure. The
better we understand this, the closer we can get to being able to imitate nature's building methods, for example. Our study has given us a new
tool to reveal a few more of the secrets of nature, and this work is
now underway," says Henrik Birkdal.


========================================================================== Story Source: Materials provided by Aarhus_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Tilman A. Gru"newald, Marianne Liebi, Nina K. Wittig, Andreas
Johannes,
Tanja Sikjaer, Lars Rejnmark, Zirui Gao, Martin Rosenthal, Manuel
Guizar- Sicairos, Henrik Birkedal, Manfred Burghammer. Mapping the
3D orientation of nanocrystals and nanostructures in human bone:
Indications of novel structural features. Science Advances, 2020;
6 (24): eaba4171 DOI: 10.1126/sciadv.aba4171 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200615115727.htm

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