Abstract Narwhal tusks are among the most intriguing structures in biology due to their immense size and unique left-handed helix. Whether this unique macroscopic homochirality originates in the structural arrangement of tusk building blocks has remained elusive. Therefore, we combined multiple structural techniques to reveal the hierarchical structure of the narwhal tusk from its building blocks (mineralized collagen fibrils) up to the macroscopic left-hand helix. Thus, we show that the macroscopic helical structure is reproduced from the molecular-scale arrangement of mineralized collagen in a double helix with opposite chirality. While mineralized collagen predominantly aligns along the tusk long axis, systematic axial deviations build helical arrangements of fibrils. Cementum has a left-hand helix of collagen fibrils, while dentine contains a right-hand arrangement extending across annual growth layers that feature distinct biomineral properties. This discovery advances understanding of how biological tissues integrate multiscale structural patterns to achieve specific mechanical and biological functions.

The possible relationship between diet and geographical locality is important for understanding the putative effects of climate change on animal behaviour and survival. Narwhals have two maxillary teeth, one of which may become a tusk. In these teeth, various chemical elements are incorporated and stored at the time of tooth formation. Here, we use inductively coupled plasma optical emission spectroscopy to investigate 12 chemical elements in tooth powder drilled from a total of 197 narwhal teeth from both sexes, tusks, embedded teeth, dentin, cementum and different geographical localities around Greenland. Additionally, the spatial distribution of Sr and Zn was mapped on a slice of tusk using X-ray fluorescence. Quantifications of Ca and P showed a mean degree of mineralization of 0.565 g g-1 and their relationship enabled the determination of the presence of approximately 1 wt% non-biomineral-associated P, which must be associated with biomolecules. While several differences were found across sampling parameters, no significant differences were found between males and females for any elements. Finally, the concentration of Cl, Ba, K and S depended on geographical locality; geographical locality was the only significant factor for Cl. These differences could potentially be linked to the circulation of freshwater from melting ice at and around Greenland.

Optimizing hydrogen and oxygen transport within porous electrodes is essential for improving the efficiency of industrial alkaline electrolyzers. In this study, we utilize operando dynamic neutron radiographic measurements to investigate gas distributions and bubble dynamics within an alkaline electrolysis cell. Porous nickel foam was used as cathode and anode in the zero-gap cell configuration to replicate the gas evolution conditions occurring in industrial settings. Our results indicate that approximately 50 % of hydrogen and oxygen is generated within the innermost quarters of both the cathode and anode at the lower section of the electrolysis cell. Additionally, the findings imply that 4-8 % of the volume within the electrode compartments remains occupied by immobilized gas bubbles. These findings demonstrate the potential of neutron imaging as a powerful technique for quantitative mapping of gas volumes within electrolyzer systems.

The stomatopod eye is a fascinating biological system capable of detecting both colour and polarization of light, making it a highly complex, mixed-tissue sample. In the investigation of complex biological systems, three-dimensional methods spanning multiple length scales with the power to resolve soft tissues are required. In this study, propagation-based phase contrast X-ray computed tomography with stitching at a 4th generation synchrotron was used to image a full stomatopod eye with sub-micron voxel size to illustrate how this method accommodates these demands. The images are based on natural X-ray contrast and without any added labels or staining agents. Key features of the eye were identified and segmented. Utilizing these segmentations, photo filter volumes, chitin porosity volumes, and muscle fiber periodicities were measured, demonstrating the ability to perform quantitative as well as qualitative investigations. Neural compartments and associated cells were discernable, showing the power of 4th generation synchrotron phase contrast for the study of soft tissues. The illustrated properties along with its non-invasive nature proves phase contrast synchrotron X-ray computed tomography with stitching to be a powerful tool for the investigation of biological materials.

Abstract The next great leap in Martian exploration is the return of samples to Earth. Maximizing their scientific value requires non‐destructive analytical techniques for early three‐dimensional characterization. Neutron computed tomography (CT), highly sensitive to hydrogen, complements conventional X‐ray CT and enables the detection of hydrous phases. The distribution and nature of hydrous phases are central to understanding the habitability, climatic and geological evolution, and potential biosignatures of Mars. Using the only Martian crustal material available on Earth, the NWA 7034 meteorite and its pairs, we demonstrate that combined neutron, X‐ray, and X‐ray diffraction CT enables non‐destructive, sample‐wide hydrogen mapping, revealing the distribution and petrographic contexts of hydrous phases. We identify hydrogen‐rich iron oxyhydroxides within ancient igneous clasts, representing a macroscopic mineralogical water reservoir. These alteration assemblages closely resemble those observed by the Perseverance rover in Jezero crater, indicating that such hydrated phases may constitute a widespread near‐surface water reservoir on early Mars.

The next great leap in Martian exploration will be the return of samples to Earth. To ensure the maximum scientific return from studying these samples, the development and utilisation of nondestructive analytical techniques are essential to enable early three-dimensional characterisation of their interiors. Neutron computed tomography is a powerful method in this context: it is highly sensitive to hydrogen and complements the more conventional X-ray computed tomography. Because the distribution and nature of hydrous phases are central to understanding the habitability, the climatic and geological evolution, and potential biosignatures of Mars, identifying hydrogenbearing phases in Martian crustal rocks is of particular importance. Using the only Martian crustal material available on Earth, the NWA 7034 meteorite and its pairs, we show that combined neutron and X-ray computed tomography enables non-destructive sample-wide mapping of hydrogen and reveals the distribution and petrographic contexts of hydrous phases. We identify hydrogen-rich iron oxyhydroxides within ancient igneous clasts, forming a macroscopic mineralogical water reservoir within the meteorite. These alteration assemblages closely resemble those observed in samples collected by the Perseverance rover in Jezero crater, where hydrated iron oxyhydroxides are also present. This similarity suggests that such phases may represent a widespread near-surface water reservoir on early Mars.

The objective of this animal study was to evaluate the osseointegration of loaded strontium-functionalized orthodontic miniscrews (Ti-Sr-O) and the effect of the Sr coating on the elemental composition of the bone as well as the coating's effects on bone mineral size and orientation. Strontium-containing coated (Ti-Sr-O) miniscrews and grade 4 titanium miniscrews (Ti) were inserted into either tibia of thirty male Wistar rats and loaded through a coil spring. After a two-, four- and six-week healing period, specimens were analyzed via histomorphometry to measure bone-to-implant contact (BIC%) and peri-implant bone formation (BF%) in defined regions of interest (ROI-1; ROI-2). Furthermore, samples were investigated at the P06 synchrotron beamline to simultaneous measure the atomic composition with X-ray fluorescence (XRF) and the crystallite size/orientation with X-ray diffraction (XRD). After two weeks Ti-Sr-O functionalized miniscrews showed significantly more bone formation in ROI-1 than in the control group with Ti miniscrews at the tension (p**=0.005) and compression side (p*=0.018). The investigation by 2D XRF and XRD Mapping with a 0.4 mu m beam resulted in multiple significant changes in comparison to the controls. The XRF showed a significant increase in the Sr/Ca level in the peri implant bone, and XRD showed significant changes in degree of orientation of the crystallographic c-axis, and for the apparent crystallite size perpendicular to the crystallographic c direction. These changes depend on the treatment and Sr/Ca level. The results suggest advantageous osseointegration of Sr-coated miniscrews under immediate loading. This resulted in changes in the microscopic organization of the bone biomineral.

Silica-carbonate biomorphs are a class of emergent materials, i.e. composite microstructures made of nanometric carbonate crystallites surrounded by amorphous silica. They form via a co-precipitation process in an interplay between alkaline earth metal carbonate and siliceous species, and self-organize into a multitude of shapes with a distinct long-range order of the carbonate nanocrystals. As model systems silica-carbonate biomorphs are frequently studied to examine the self-organization of life-like structures under extreme geochemical conditions. Further, due to their optical properties they lend themselves as a platform for optical, electronic or magnetic functionalization. A big hurdle in this task is our incomplete understanding of the underlying formation process and how the interplay between synthesis parameters affects important nanoscale properties such as crystalline structure and texture, as well as the shape on the microscale. Here, we use X-ray texture and diffraction tomography to unveil the local crystalline texture in 3D of silica-witherite biomorphs. We find surprisingly different growth motifs across different morphologies, but also that the crystalline properties vary significantly within a single structure. We distinguish different growth regimes which we discuss, connecting experimental findings with present literature on biomorphs as well as with silicate chemistry. We observe a systematic change of crystalline properties across and within the different morphologies. On this basis, we provide a detailed unified scheme that links the measured spatially resolved crystalline properties of the distinct complex morphologies with the existing literature models on their growth, underlining the importance of silicate oligomerization for the formation of biomorphs.

The intricate porous network of cryogels enhances diffusivity, injectability, and shape-recovery properties, providing a valuable tool for minimally invasive biomedical applications. However, the injection of cell-loaded complex structures remains highly challenging. Here, we demonstrate the freeform 3D printing of fully protein-based macroporous cryogels with cell-adsorptive and shape-recoverable features. The 3D-printed cryogels surpass conventional cryogels, revealing successful injection, cell-adsorptive features, and a high interconnected porosity (99.2%). The rapid hydration process enables the efficient incorporation of individual cells or spheroids into the cryogel network. Using an in-liquid cell aspiration method, the constructs retained cellular content up to 89%, with in vitro culture revealing high viability and cell spreading over 14 days. Our findings highlight the potential of the cryogels’ macroporosity for cell loading and injectability. We anticipate that these off-the-shelf cryogels will pave the way for a new generation of self-adsorptive and injectable cryogels.

Accurate 3D characterization of osteocyte lacunae is important when investigating the role of osteocytes under various physiological and pathological conditions but remains a challenge. With the continued development of laboratory X-ray micro-computed tomography, an increasing number of studies employ these techniques beyond traditional bone morphometry to quantify osteocyte lacunae. However, there is a lack of knowledge on the effect of measurement parameters on the image quality and resolution and in turn the osteocyte lacunar quantification. Herein, we have examined the interplay between scan parameters and the resultant lacunar quantification in terms of lacunar size, shape, and density by comparison with a synchrotron benchmark dataset. We summarize our conclusions in a guide for use of μ-CT for osteocyte lacunar quantification: (1) Identification of the measurement requirements to address the research questions. (2) Collection and preparation of suitable sample(s) that fulfills these requirements. (3) Experimental considerations including determination of the required voxel size, in turn dictating the maximum FOV and by extension the maximum size of the sample(s). The experimental parameters chosen should ensure optimal image contrast, sufficient signal to noise, angular sampling etc. Usually, it is advisable to measure as well as possible within the limits of time, budget, data storage and analysis capabilities. (4) Data analysis and reporting of the results, including visual examination of the data at multiple steps in the analysis, to ensure correct feature identification and suitable reporting approaches. (5) Cross study comparisons, which may be unsuitable if the experimental conditions and analysis strategies are not comparable.

Hard tissues in biology are typically hierarchical composites. Osteoderms are mineralized dermal structures, widespread in lizards, in which a hyper‐mineralized superficial layer, the capping tissue, has recently attracted attention for its unusual structural and mechanical features, with, e.g., moduli reaching those of enamel. Here, a comparative study of osteoderms from six lizard species whose osteoderms bear capping tissue ( Heloderma horridum , Pseudopus apodus , Broadleysaurus major , Corucia zebrata , Tiliqua scincoides , and Tiliqua rugosa ) are presented using X‐ray computed tomography, nanoindentation mapping, synchrotron X‐ray diffraction/fluorescence imaging, and finite element modeling. The capping tissue is consistently more mineralized than the underlying bone across all species. Mechanical testing shows that the capping tissue is stiffer and harder than bone, but its mechanical properties range widely, from values only slightly exceeding those of bone to enamel‐like levels. Two extreme architectures are observed: H. horridum and B. major exhibit unusually large, near‐isotropically arranged crystals and exceptional stiffness, while the other species display smaller crystals, are more textured than bone, and have less extreme stiffness. This demonstrates that capping tissue is a morphologically and functionally diverse specialization, highlighting its potential role in the evolutionary adaptation of osteoderms.

Osteoderms, skeletal structures in the skin, are found in many animals and serve diverse roles. In some lizards, the bony osteoderm has a capping tissue (CT) whose composition and structure remain unknown. Here, the composition and nanostructure of osteoderms from the Mexican beaded lizard (Heloderma horridum) are investigated. The CT is highly mineralized with an extraordinarily high elastic modulus. Within the osteoderm, a transition zone between capping and bone tissue forms a graded increase in mineralization towards the superficial CT. Unlike other examples of mineralized tissues, the CT demonstrates a new combination of physical properties and nanostructural organization. It displays stiffness and hardness similar to enamel, and hydroxyapatite crystals that are an order of magnitude larger than those within the bone tissue and are, thus, reminiscent of enamel crystals. However, in stark contrast to enamel, the CT displays only minimal preferred orientation of the crystallites. Thus, it achieves very high mechanical properties with enamel-like crystal sizes but with near-isotropic microstructural orientation. The Mexican beaded lizard CT presents a highly unusual structural design resulting in high-performance mechanics. STATEMENT OF SIGNIFICANCE: The stiffest tissue in vertebrates is enamel, which is characterized by large, highly oriented nanocrystals. The less stiff bone has smaller nanocrystals and a lower, but still high degree of texture. The osteoderms of the Mexican beaded lizard are herein investigated by a combination of mechanical testing, spatially resolved X-ray diffraction and fluorescence, and 3D X-ray imaging. Surprisingly, the osteoderms have a capping tissue with enamel-like stiffness, significantly larger crystals than the underlying bone but are much less textured. This provides a new type of design for hard biological tissues.

Bone contains diverse structures. In fast-growing large animals, fibrolamellar bone is formed first and is then gradually replaced by remodelled bone with secondary osteons. Using position-resolved X-ray diffraction and X-ray fluorescence as a 2D multimodal microscopy technique, the nature of biomineral nanocrystals is investigated in bovine bone. Systematic spatial variations are found, for example, with the crystallite size increasing with distance from the bone growth front. The growth front is found to be sharply enriched in Zn, which is speculated to be related to the presence of metal-containing enzymes. Upon remodelling, the formed secondary osteons have a lower degree of mineralization, different lattice constants, and smaller nanocrystal sizes than the primary bone. The results underline the need for spatially resolved techniques for understanding bone biomineralization.

Soft conductive materials are of interest for a wide range of applications, but their syntheses have remained difficult. Herein, we present a convenient route for underwater fabrication of a composite made of carbon nanotubes (CNTs) and mussel-inspired complex coacervates. The key to success of this method is that CNTs were solubilized very effectively in protocoacervates, which are high-concentration solutions of polyelectrolytes at a pH where only one of them is charged, thereby impeding coacervate formation. Composite materials were formed by the simple injection of CNT-dispersed protocoacervate solutions into water under ambient conditions. The method is simple, fast, and ecofriendly, and composites of CNT-complex coacervate in the form of films or bulk materials were obtained. The composites demonstrated electrical conductivity and tunable mechanical properties, which depended on the concentration of polyelectrolytes and the CNT:protocoacervate ratio. Hence, the composites can be manipulated to attain diverse properties, for examples, tunable reduced modulus (15 to 32 GPa) and hardness (0.3 to 0.7 GPa) as well as an electrical conductivity of up to 4 x 10(3) S m(-1).

Biological materials have outstanding properties. With ease, challenging mechanical, optical or electrical properties are realised from comparatively `humble' building blocks. The key strategy to realise these properties is through extensive hierarchical structuring of the material from the millimetre to the nanometre scale in 3D. Though hierarchical structuring in biological materials has long been recognized, the 3D characterization of such structures remains a challenge. To understand the behaviour of materials, multimodal and multi-scale characterization approaches are needed. In this review, we outline current X-ray analysis approaches using the structures of bone and shells as examples. We show how recent advances have aided our understanding of hierarchical structures and their functions, and how these could be exploited for future research directions. We also discuss current roadblocks including radiation damage, data quantity and sample preparation, as well as strategies to address them.