Synchrotron based reserach
The biomechanics group is regular users of several synchrotron facilites around Europe, including MAXLAB in Lund, Sweden, Swiss Light Source (Paul Sheerer Institute) in Switzerland, and Diamond Light Source, in the UK. We are especially proud to have been one of the first user groups at the new MAX-IV facility in Lund.
A synchrotron is a very powerful source of X-rays. The X-rays are produced when high energy electrons circulate around the synchrotron. All synchrotron science is based on the physical phenomenon that when a moving electron changes direction, it emits energy. When the electron is moving fast enough, the emitted energy is at X-ray wavelength. The synchrotron accelerates the electrons to move very fast, and thereby emitt high energy in the X-ray wavelength, by making them change direction periodically. The resulting X-rays are directed toward an experimental station, called beamline, where specific type of experiments can take place.
Fourier Transform Infrared Spectroscopy (FTIR) is based on detecting the absorption of infrared (IR) radiation into chemical bonds of molecules. FTIR enables mapping of the composition at discrete points in a thin sections of a tissue. Molecules absorb IR-radiation at specific wavelengths based on their chemical functional groups; therefore IR-spectroscopy can be thought of as a molecular fingerprint. FTIR is widely used to analyze biological tissues since each tissue component has a unique spectral signature, its chemical composition can be determined.
We use infrared spectroscopy to quanitfy the molecular composition of bone, cartilage and tendon tissues. Based on the spectra, the amount of collagen and mineral (often presented as the ration between the two) can be obtained. Also, information linked to the maturity of the collagenous phase (related to collagen crosslinks) and the mineral phase (acid phosphate content and crystalinity) can be quantified.
Example of IR spectroscopy at D7-beamline, MAXLAB (Khayyeri et al., Sci Reports, 2017).
Small Angle X-ray scattering
Small Angle X-ray Scattering (SAXS) is can quanitfy differences in nanoscale density in a sample. It can determine the size, orientation and structure of the nanosize particles. The information in obtained by analysing the scattering behavior of Xrays when they travel through the material at very small angles (typically 0.1 - 10°). SAXS can be used to obtain structural information of dimensions between 1 and 100 nm. Therefore, it is a very useful technique for characterization of materials and biological tissues.
We use small angle X ray scattering to study the collagen and mineral nanostructure in bone and the collagen in tendons. We also perform experiments in situ, thus under simultanous mechanical load, which enable us to understand how the material components are affected and damaged by different types of loading.
Left: Example of in situ SAXS setup from I911-4 beamline, MAXLAB (Gustafsson et al., in review. 2017). Right: Example of scattering from cortical bone (Turunen et al., J Biomed Optics, 2014).
High resolution imaging
X-ray microtomography is based on the same principle as a computed tomography system in a hospital. It uses x-rays to create 2D cross-sections of a physical object, that is then rotated slightly before the next cross-section imaging is obtained. Based on many of these 2D images, a virtual 3D model of the sample can be created without destroying the original sample. At synchrotron facilites, when very high energies are avialable, the images have better signal to noise and allows for much faster images to be obtained with higher image resolution.
We use 3D imaging with or without phase constrast to obtain micro structural information in 3D about bone and cartilage. We also perform experiments in situ, thus under simultanous mechanical load, which enable us to understand how the microstructure of the tissue is affected by different types of loading.
Example of high resolution imaging from TOMCAT (PSI) when implant-pullout is studied (Le Cann, in progress)
Neutron based research
The biomechanics group are rather new users of Neutrons, with some experience from Swiss Spallation Source (Paul Sheerer Institute) in Switzerland, and Institut Laue-Langevin (ILL) in France. However, we are highly interseted in exploring the potential with the upcoming new European Spallation Source in Lund, Sweden.
A spallation source is an accelerator based neutron facility that provides neutron beams. Neutron scattering when the neutrons interact with matter can then be used to study behavior of materials and biological tissues. The European Spallation Source will become one of the world's most powerful neutron sources, that will enable fantastic oppertunites for multi-disciplinary research related to materials, energy, health and the environment.
Neutron tomographic imaging
Neutron microtomography is based on the same principle as X-ray microtomography. It uses neutrons to create 2D cross-sections of a physical object, that is then rotated slightly before the next cross-section imaging is obtained. Based on many of these 2D images, a virtual 3D model of the sample can be created without destroying the original sample. Compared to X-rays which are highly absorbed by larger atoms, neutrons are more heavily absorbed by lighter elements, such as hydrogen. Thus, the constrast in the images are very different with X-rays and neutrons.
We have used neutron tomography to study bone-implant ingrowth with metal implants, since metals are often resulting in artefacts when imaged with x-rays.
Example from study comparing Neutron and X-ray tomography to study on bone-implant ingrowth (Isaksson et al., Bone, 2017).
Small Angle Neutron Scattering
Small Angle Neutron Scattering (SANS) uses elastic neutron scattering at small scattering angles to study the structure of e.g. tissues at the nanoscale. It is in many ways similar to its X-ray based counter part (SAXS, see above), but SANS is more sensitivity to light elements.
We have performed pilot experiement with SANS to understand the collagen structure in bone tissue.