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Abstract: Bioinspired de novo self-assembling peptides have been widely used for the development of soft biomaterials for a wide variety of biomedical and pharmaceutical applications, such as cell scaffolding for tissue engineering1, controlled and localised drug delivery2, biosensing3, and many others. The meticulous control of peptide-based nanomaterial properties over the length scale, by molecular design, remains the main challenge for tailoring biomaterials properties to meet the application needs. In our group, we have recently adopted a minimalistic molecular engineering approach for the development of Ultrashort Ionic-complementary Constrained Peptides (UICPs), which were rationally designed to self-assemble into amphiphilic β-sheet nanofibers with unique hydrogelation properties and surface activity.4 We have previously demonstrated the crucial role played by aromatic stacking for the formation and thermodynamic stabilisation of UICP β-sheet structures. Herein, we will show how charge interactions can be manipulated for fine tuning molecular self-assembly, morphology and size of nanofibrous structures formation and viscoelasticity of UICP hydrogels. A library of 18 peptide sequences (4-5 residues long) was developed to study the effect of the sequence net charge, charge density distribution, reversal of charge order and ionic self-complementarity on their propensity towards self-assembly and gelation. Interestingly, 12 of these peptides self-assembled into β-sheet nanofibrous structures forming hydrogels at pH 4.5-5, as confirmed by ATR-FTIR, SEM, TEM, SAXS and oscillatory rheology. Full control over β-sheet content (ranging from ~30-80%), fibre morphology (thin fibrils, thick straight fibre bundles, twisted helical nanofibres, flat nanoribbons and nanotubes) and sizes (~4-67 nm in diameter), as well as gelation (critical gelation concentrations ranging from <7.5 to >100 mM) and viscoelastic properties (storage moduli G’ ~0.1-100 KPa) was achieved by the careful positioning of both Glu and Lys residues at both C- and N-termini, in the sequence core and on both the hydrophilic and hydrophobic faces of the peptide chain. In essence, this design approach enabled/disabled lateral growth along the β-sheet ladder via electrostatic attraction (counter charge, anion-pi and cation-pi)/repulsion, hence controlling fibre thickness, morphology, entanglement, and the resulting viscoelasticity of the system. Our UICPs platform thus provides the flexibility in peptide molecular design for the manufacturing of soft biomaterials with versatile properties that can be in future tailored to the relevant biomedical application.

Open Access

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Abstract: Composites of sodium-exchanged zeolite chabazite particles with attached superparamagnetic nanoparticles of Fe3O4 and CoFe2O4 ferrite spinels have been produced using a novel solvothermal route. These have been characterized by a combination of techniques, including powder x-ray diffraction, x-ray fluorescence spectroscopy, vibrating sample magnetometry, and both scanning and transmission electron microscopy. These confirm the nature of the attached nanoparticles, and the microscope images show a good dispersion of nanoparticles with a narrow size range deposited uniformly on the surface of the zeolite particles. The magnetization is of sufficient strength to allow magnetic separation from a solution. Both time and pH dependent Cs uptake experiments show that the magnetized systems are still excellent for the rapid uptake of Cs via an ion exchange process with no reduction in property due to the attached nanoparticles.

Open Access

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Abstract: Correlative multimodal imaging is a useful approach to investigate complex structural relations in life sciences across multiple scales. For these experiments, sample preparation workflows that are compatible with multiple imaging techniques must be established. In one such implementation, a fluorescently labeled region of interest in a biological soft tissue sample can be imaged with light microscopy before staining the specimen with heavy metals, enabling follow-up higher resolution structural imaging at the targeted location, bringing context where it is required. Alternatively, or in addition to fluorescence imaging, other microscopy methods, such as synchrotron x-ray computed tomography with propagation-based phase contrast or serial blockface scanning electron microscopy, might also be applied. When combining imaging techniques across scales, it is common that a volumetric region of interest (ROI) needs to be carved from the total sample volume before high resolution imaging with a subsequent technique can be performed. In these situations, the overall success of the correlative workflow depends on the precise targeting of the ROI and the trimming of the sample down to a suitable dimension and geometry for downstream imaging. Here, we showcase the utility of a femtosecond laser (fs laser) device to prepare microscopic samples (1) of an optimized geometry for synchrotron x-ray tomography as well as (2) for volume electron microscopy applications and compatible with correlative multimodal imaging workflows that link both imaging modalities.

Open Access

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Abstract: Serial femtosecond crystallography was initially developed for room-temperature X-ray diffraction studies of macromolecules at X-ray free electron lasers. When combined with tools that initiate biological reactions within microcrystals, time-resolved serial crystallography allows the study of structural changes that occur during an enzyme catalytic reaction. Serial synchrotron X-ray crystallography (SSX), which extends serial crystallography methods to synchrotron radiation sources, is expanding the scientific community using serial diffraction methods. This report presents a simple flow cell that can be used to deliver microcrystals across an X-ray beam during SSX studies. This device consists of an X-ray transparent glass capillary mounted on a goniometer-compatible 3D-printed support and is connected to a syringe pump via light­weight tubing. This flow cell is easily mounted and aligned, and it is disposable so can be rapidly replaced when blocked. This system was demonstrated by collecting SSX data at MAX IV Laboratory from microcrystals of the integral membrane protein cytochrome c oxidase from Thermus thermophilus, from which an X-ray structure was determined to 2.12 Å resolution. This simple SSX platform may help to lower entry barriers for non-expert users of SSX.

Open Access

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Abstract: Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical–chemical–structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.