Scientists from the Center for Free-Electron Laser Science (CFEL) have developed a groundbreaking technique for imaging biological structures using high-energy X-rays without causing damage to the samples. Led by Saša Bajt and Henry Chapman, the team utilized the PETRA III synchrotron light source at DESY to generate high-resolution X-ray images of dried biological material without the need for freezing, coating, or other alterations. The technique, which relies on diffractive lenses to focus high-energy X-rays, allows for imaging at less than 1% of the X-ray damage threshold of the sample. The results of their study, published in the journal Light: Science & Applications, demonstrate the potential of this method for future applications in brighter next-generation light sources like PETRA IV.
When X-rays interact with biological material, the resulting effects depend on the energy and intensity of the X-rays. Lower-energy X-rays are absorbed by the atoms in the sample, causing damage due to the energy transfer. Higher-energy X-rays, on the other hand, undergo elastic scattering, where they bounce off the matter without depositing their energy. This interaction is utilized in techniques such as crystallography and ptychography, but absorption and subsequent damage to the sample still occur. The CFEL team explored a third interaction called Compton scattering, which involves X-rays leaving only a small amount of energy in the target material. This method had been overlooked due to the lack of suitable high-resolution lenses for higher X-ray energies.
To address this challenge, the team developed multilayer Laue lenses, which consist of nanometer-thin alternating layers of silicon carbide and tungsten carbide. These lenses enabled efficient focusing of the X-ray beam for imaging. Using the lens system and the PETRA III beamline P07, the team successfully imaged various biological materials by detecting Compton scattering data as the sample was exposed to the focused beam. PETRA III provided the necessary brightness at high X-ray energies to acquire images in a reasonable time frame. The team achieved a resolution of 70 nanometers for each sample, with minimal radiation damage left behind.
The researchers note that a spherical detector would further enhance the results since X-rays emitted from the sample scatter in all directions. With a brighter source, such as the planned PETRA IV facility, the method could achieve resolutions of up to 10 nanometers without causing damage. This advancement opens up possibilities for imaging whole unsectioned cells or tissues, tracking nanoparticles within cells, and investigating non-biological subjects like battery mechanics. The team highlights the novelty of their technique, emphasizing that there is much to explore in the future.
Source: Deutsches Elektronen-Synchrotron