B21-High Throughput SAXS
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Diamond Proposal Number(s):
[23247]
Abstract: Nanofibres are an interesting phase into which amphiphilic molecules can self-assemble. Described for a large number of synthetic lipids, they were seldom reported for natural lipids like microbial amphiphiles, known as biosurfactants. In this work, we show that the palmitic acid congener of sophorolipids (SLC16:0), one of the most studied families of biosurfactants, spontaneously forms a self-assembled fibre network (SAFiN) at pH below 6 through a pH jump process. pH-resolved in situ small-angle X-ray scattering (SAXS) shows a continuous micelle-to-fibre transition, characterized by an enhanced core–shell contrast between pH 9 and pH 7 and micellar fusion into a flat membrane between pH 7 and pH 6, approximately. Below pH 6, homogeneous, infinitely long nanofibres form by peeling off the membranes. Eventually, the nanofibre network spontaneously forms a thixotropic hydrogel with fast recovery rates after applying an oscillatory strain amplitude out of the linear viscoelastic regime: after being submitted to strain amplitudes during 5 min, the hydrogel recovers about 80% and 100% of its initial elastic modulus after, respectively, 20 s and 10 min. Finally, the strength of the hydrogel depends on the medium's final pH, with an elastic modulus fivefold higher at pH 3 than at pH 6.
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Sep 2021
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[22575, 20132]
Abstract: Digital volume correlation (DVC) in combination with high-resolution micro-computed tomography (microCT) imaging and in situ mechanical testing is gaining popularity for quantifying 3D full-field strains in bone and biomaterials. However, traditional in situ time-lapsed (i.e., interrupted) mechanical testing cannot fully capture the dynamic strain mechanisms in viscoelastic biological materials. The aim of this study was to investigate the time-resolved deformation of bone structures and analogues via continuous in situ synchrotron-radiation microCT (SR-microCT) compression and DVC to gain a better insight into their structure-function relationships. Fast SR-microCT imaging enabled the deformation behaviour to be captured with high temporal and spatial resolution. Time-resolved DVC highlighted the relationship between local strains and damage initiation and progression in the different biostructures undergoing plastic deformation, bending and/or buckling of their main microstructural elements. The results showed that SR-microCT continuous mechanical testing complemented and enhanced the information obtained from time-lapsed testing, which may underestimate the 3D strain magnitudes as a result of the stress relaxation occurring in between steps before image acquisition in porous biomaterials. Altogether, the findings of this study highlight the importance of time-resolved in situ experiments to fully characterise the time-dependent mechanical behaviour of biological tissues and biomaterials and to further explore their micromechanics under physiologically relevant conditions.
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Jun 2021
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B21-High Throughput SAXS
B23-Circular Dichroism
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Diamond Proposal Number(s):
[21035]
Abstract: One of the major challenges within the emerging field of injectable stem cell therapies for articular cartilage (AC) repair is the retention of sufficient viable cell numbers at the site of injury. Even when delivered via intra-articular injection, the number of stem cells retained at the target is often low and declines rapidly over time. To address this challenge, an artificial plasma membrane binding nanocomplex was rationally designed to provide human mesenchymal stem cells (hMSCs) with increased adhesion to articular cartilage tissue. The nanocomplex comprises the extracellular matrix (ECM) binding peptide of a placenta growth factor-2 (PlGF-2) fused to a supercharged green fluorescent protein (scGFP), which was electrostatically conjugated to anionic polymer surfactant chains to yield [S−]scGFP_PlGF2. The [S−]scGFP_PlGF2 nanocomplex spontaneously inserts into the plasma membrane of hMSCs, is not cytotoxic, and does not inhibit differentiation. The nanocomplex-modified hMSCs showed a significant increase in affinity for immobilised collagen II, a key ECM protein of cartilage, in both static and dynamic cell adhesion assays. Moreover, the cells adhered strongly to bovine ex vivo articular cartilage explants resulting in high cell numbers. These findings suggest that the re-engineering of hMSC membranes with [S−]scGFP_PlGF2 could improve the efficacy of injectable stem cell-based therapies for the treatment of damaged articular cartilage.
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Jun 2021
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B21-High Throughput SAXS
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Diamond Proposal Number(s):
[24306]
Open Access
Abstract: Capsular antigen fragment 1 (Caf1) is an oligomeric protein consisting of 15 kDa monomeric subunits that are non-covalently linked through exceptionally strong and kinetically inert interactions into a linear polymer chain. It has been shown that after its thermal depolymerisation into unfolded monomeric subunits, Caf1 is able to efficiently repolymerise in vitro to reform its polymeric structure. However, little is known about the nature of the repolymerisation process. An improved understanding of this process will lead to the development of methods to better control the lengths of the repolymerised species, and ultimately, to better design of the properties of Caf1-based materials. Here we utilize small-angle X-ray scattering to estimate the size of Caf1 polymers during the first 24 h of the re-polymerisation process. Analytical ultracentrifugation measurements were also used to investigate the process post-24 h, where the rate of repolymerisation becomes considerably slower. Results show that in vitro polymerisation proceeds in a linear manner with no evidence observed for the formation of a lateral polymer network or uncontrolled aggregates. The rate of Caf1 in vitro repolymerisation was found to be concentration-dependent. Importantly, the rate of polymer growth was found to be relatively fast over the first few hours, before continuing at a dramatically slower rate. This observation is not consistent with the previously proposed step-growth mechanism of in vitro polymerisation of Caf1, where a linear increase in polymer length would be expected with time. We speculate how our observations may support the idea that the polymerisation process may be occurring at the ends of the chains with monomers adding sequentially. Our findings will contribute towards the development of new biomaterials for 3D cell culture and bio-printing.
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May 2021
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B18-Core EXAFS
I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[18595, 18923, 21525]
Abstract: Phosphate-based glasses (PBGs) are traditionally prepared using the high-temperature melt-quenching (MQ) route or via the more recent sol–gel (SG) method that requires the use of organic solvents. The coacervation method represents an excellent inexpensive and green alternative to MQ and SG, being performed in aqueous solution and at room temperature. Coacervation is particularly applicable for the production of PBGs designed for biomedical applications because it allows for the inclusion of temperature-sensitive molecules and does not require the use of toxic solvents. Whereas the atomic structure of the MQ and SGPBGs is known, the atomic structure of those prepared via coacervation has yet to be investigated. In this study, a comprehensive advanced structural characterization has been performed on phosphate-based glasses in the system P2O5–CaO–Na2O–Ag2O (Ag2O mol % = 0, 1, 3, 5, 9, and 14) prepared via the coacervation method. Glasses within this system should find application as bioresorbable biomaterials thanks to their ability to release bioactive ions in a controlled manner. In particular, they possess antibacterial properties, inferred by the release of Ag+ over time. High-energy X-ray diffraction (HEXRD), 31P and 23Na solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR), and X-ray absorption Spectroscopy (XAS) at the Ag K-edge were used to probe the atomic structure of the glasses after drying in vacuum and after calcination at 300 °C. The length of the polyphosphate chains in the solid state appears to be independent of silver concentration; however, significant degradation of these chains is seen after calcination at 300 °C. Atomic-scale characterisation results indicate that the structure of these glasses is akin to that of other silver-doped phosphate glasses prepared using the MQ and SG methods. This suggests that phosphate-based glasses prepared using milder and greener conditions may have similar chemical and physical properties such as solubility, biocompatibility, and antibacterial properties.
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May 2021
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[15444]
Abstract: Inorganic/organic hybrids have co-networks of inorganic and organic components, with the aim of obtaining synergy of the properties of those components. Here, a silica-gelatin sol-gel hybrid “ink” was directly 3D printed to produce 3D grid-like scaffolds, using a coupling agent, 3-glycidyloxypropyl)trimethoxysilane (GPTMS), to form covalent bonds between the silicate and gelatin co-networks. Scaffolds were printed with 1 mm strut separation, but the drying method affected the final architecture and properties. Freeze drying produced <40 μm struts and large ~700 μm channels. Critical point drying enabled strut consolidation and optimal mechanical properties, with ~160 μm struts and ~200 μm channels, which improved mechanical properties. This architecture was critical to cellular response: when chondrocytes were seeded on the scaffolds with 200 μm wide pore channels in vitro, collagen Type II matrix was preferentially produced (negligible amount of Type I or X were observed), indicative of hyaline-like cartilaginous matrix formation, but when pore channels were 700 μm wide, Type I collagen was prevalent. This was supported by Sox9 and Aggrecan expression. The scaffolds have potential for regeneration of articular cartilage regeneration, particularly in sports medicine cases.
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Feb 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[10311, 16292, 18524]
Abstract: Soft biological tissues have a hierarchical architecture from the molecular to the macroscale, with structure-function relations at each level crucial for function. In developing new soft biomaterials for medical applications, understanding, and emulating these mechanisms will provide essential guidance. In this chapter we review how time- and position-resolved synchrotron small-angle x-ray scattering (SAXS) combined with multiscale mechanical modelling can illuminate such small-scale mechanisms, using the examples of articular cartilage and the mutable connective tissue of echinoderms. In articular cartilage, SAXS reveals a gradient in fibrillar-level pre-strain, which is suppressed either by physiological static loading or by enzymatic modifications mimicking ageing, and modelling of the fibril/proteoglycan network shows that the pre-strain reflects the local internal swelling pressure. In mutable connective tissue, our results show that interfibrillar stiffening and de-stiffening enables its rapid alterations in mechanical properties, whose kinetics can be captured by analytical modelling of the structure. The combination of multiscale modelling and in situ SAXS thus shows potential of investigating and elucidating the mechanisms enabling function in both natural tissues as well as in new soft biomaterials mimicking their structure.
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Jan 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[20409]
Open Access
Abstract: In this paper, the microstructural, optical, thermal, crystallization, and water absorption properties of films prepared from never‐dried (ND) and freeze‐dried (FD) cellulose nanocrystals (CNCs) are reported. Morphology of the ND CNCs reveals a needle‐like structure, while after freeze‐drying, they show a flake‐like morphology. Microstructural analysis of ND and FD CNCs are further studied via small angle X‐ray scattering to probe interactions. ND CNCs yield a transparent film with a low surface roughness (14 ± 4 nm), while the FD CNC film evidence a significant reduction of their transparency due to their higher surface roughness (134 ± 20 nm). Although Fourier transform infrared spectroscopy and energy‐dispersive X‐ray spectroscopy analyses reveal no chemical change occurs during the freeze‐drying process, yet a more intense thermal degradation profile is observed for FD CNC film, probably due to the higher oxygen ingress within the gaps created between the stacked flakes. This, in turn, results in a greater loss of crystallinity at a higher temperature (300 °C) compared to the ND CNC film. A rapid decrease in water contact angle of the FD CNC film proves that the morphology of flakes and their orientation within the film has a strong influence in increasing water absorption capacity.
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Nov 2020
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Michaela
Sulikova
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Zuzana
Molčanová
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Beata
Ballóková
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Juraj
Durisin
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Slávka
Martinková
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Dagmara
Varcholová
,
Stefan
Michalik
,
Robert Tang
Kong
,
Logan
Ward
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Apurva
Mehta
,
Katarína
Sulova
,
Miloš
Fejercak
,
Andrea
Lachova
,
Róbert
Džunda
,
Karel
Saksl
Abstract: In surgery, in addition to joint replacement, which requires permanent implantation of the prosthesis into the human body, there are many other clinical cases where fixation or mechanical support are only temporarily needed during the healing process of the injured or pathological tissue. In this case, biodegradable materials are the optimal choice as these materials do their job and degrade in the human body thereafter. Amorphous magnesium-zinc based alloys are nowadays a very promising group of metallic glasses (MGs). Unfortunately, the brittleness of Mg-Zn MGs and poor glass forming ability (GFA) have hindered their further application. We have developed a composition series of completely new (not published) ternary Mg-Zn-Sr alloys with attractive properties in terms of possible future applications (density comparable to human bones, wide supercooled liquid region, low rate of degradability, etc.). These ternary alloys will serve as precursors for design of future highly alloyed systems with tuned mechanical properties and dissociation rate in human body.
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Nov 2020
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[13002]
Open Access
Abstract: The importance of the microstzructure of silicone hydrogels is widely appreciated but is poorly understood and minimally investigated. To ensure comfort and eye health, these materials must simultaneously exhibit both high oxygen and high water permeability. In contrast with most conventional hydrogels, the water content and water structuring within silicone hydrogels cannot be solely used to predict permeability. The materials achieve these opposing requirements based on a composite of nanoscale domains of oxygen‐permeable (silicone) and water‐permeable hydrophilic components. This study correlated characteristic ion permeation coefficients of a selection of commercially available silicone hydrogel contact lenses with their morphological structure and chemical composition. Differential scanning calorimetry measured the water structuring properties through subdivision of the freezing water component into polymer‐associated water (loosely bound to the polymer matrix) and ice‐like water (unimpeded with a melting point close to that of pure water). Small‐angle x‐ray scattering, and environmental scanning electron microscopy techniques were used to investigate the structural morphology of the materials over a range of length scales. Significant, and previously unrecognized, differences in morphology between individual materials at nanometer length scales were determined; this will aid the design and performance of the next generation of ocular biomaterials, capable of maintaining ocular homeostasis.
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Jul 2020
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