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Fig. 4: Imprints of destruction in bone collagen caused by different synchrotron experiments. a) Schematic illustration of XRD performed at BESSY II and µCT performed at beamline ID19. b) SHG microscopy reveals collagen fibres and shows visible damage (black) to collagen (white) following measurements by: 1) µCT, 2) XRD-µCT and 3) XRD. c) Damage progression in collagen over time observed in bones of different animals, revealed by SHG.

Micrometre-resolution X-ray beams have been used to study bone radiation damage observed by confocal laser scanning microscopy. The data uncovered the mechanism involved in the destruction of collagen fibres, ionised by electrons that are emitted from the mineral nanocrystals in the bony nanocomposite.

It has long been known that X-rays damage living tissue. For this reason, there are clear medical recommendations to keep exposure to X-rays to a minimum. But X-ray imaging and analysis are considered non-destructive in basic research, especially when characterising mineralised tissue samples such as bone. Researchers rely on increasingly powerful X-ray sources to perform tomography or diffraction measurements at ever- increasing resolutions and speeds. Such experiments have become standard for bone research and have yielded countless insights into healthy and diseased tissues.

The prevailing concept was that the higher the flux and resolution, the better the measurements. Recent advances in automated image processing and the growing availability of artificial intelligence tools make the case for achieving faster data acquisition rates, larger numbers of datapoints or a greater number of images for better quality or higher resolution. For bone studies, the radiation dose relies on simple assumptions of absorption per mass, with recommendations to keep measurements below a 11 kGy damage threshold. As compelling as this may appear, the composite nature of bone was somehow overlooked specifically, heavier, photon-absorbing calcium crystals residing in the polymer mesh of collagen

X-ray irradiation of bone nanocomposites induces damage in collagen due to high-energy photoelectron excitation