I07-Surface & interface diffraction
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Abstract: The adsorption of peptides on metal oxides is an area of significant interest, both fundamentally and in a number of technologically important areas. These range from the integration of biomaterials in the body, to denaturation of protein therapeutics and the use of biomolecules and bioinspired materials in synthesis and stabilization of novel nanomaterials. Here we present a study of the tripeptide arginylglycylaspartic acid (RGD) on the surfaces of vacuum-prepared single crystalline TiO2(110), pyrocatechol-capped TiO2(110), and model SLA and SLActive dental implant samples. X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy show that the RGD adsorption mode on the single crystal is consistent with bonding through the deprotonated carboxylate groups of the peptide to surface Ti atoms of the substrate. Despite the increased hydrophobicity of the pyrocatechol-capped TiO2(110) surface RGD adsorption from solution increases following this surface treatment. RGD adsorption on SLA and SLActive surfaces shows that the SLActive surface has a greater uptake of RGD. The RGD uptake on the pyrocatechol capped single crystal and the model implant surfaces suggest that the ease with which surface contaminant hydrocarbons are removed from the surface has a greater influence on peptide adsorption than hydrophobicity/hydrophilicity of the surface.
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Jul 2019
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K.
Saksl
,
Z.
Molčanová
,
J.
Durisin
,
S.
Michalik
,
L.
Temleitner
,
B.
Balloková
,
V.
Girman
,
Y.
Katuna
,
M.
Sulikova
,
K.
Sulova
,
M.
Fejercak
,
M.
Lisnichuk
,
A.
Lachová
,
L.
Kapuscinský
Abstract: Very low density eutectic Ca72Mg28 at.% alloy is a precursor of complex biodegradable alloys with potential use as bioresorbable alloy for orthopaedic applications. The structure of the amorphous alloy was investigated by using X-ray, neutron diffraction and reverse Monte Carlo (RMC) modelling. The RMC configuration was decomposed into polyhedral holes whose faces are all triangles consisting of chemical bonds. Free volumes in the respective polyhedral holes were evaluated with reference to the packing efficiency of crystalline CaMg2 HCP phase. The tetrahedral holes, accounting for about 55% of the whole space, are regarded as densely packed units because the average packing efficiency of them is approximately equal to that of the corresponding crystal phase. At the same time, various types of polyhedral holes which have a certain free volume have been observed, and some of them are connected with each other. The densely packed coordination polyhedra consisting only of tetrahedral holes tend to be clustered.
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Jun 2019
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[13241]
Open Access
Abstract: Bioglass® was the first material to form a stable chemical bond with human tissue. Since its discovery, a key goal was to produce three-dimensional (3D) porous scaffolds which can host and guide tissue repair, in particular, regeneration of long bone defects resulting from trauma or disease. Producing 3D scaffolds from bioactive glasses is challenging because of crystallization events that occur while the glass particles densify at high temperatures. Bioactive glasses such as the 13–93 composition can be sintered by viscous flow sintering at temperatures above the glass transition onset (Tg) and below the crystallization temperature (Tc). There is, however, very little literature on viscous flow sintering of bioactive glasses, and none of which focuses on the viscous flow sintering of glass scaffolds in four dimensions (4D) (3D + time). Here, high-resolution synchrotron-sourced X-ray computed tomography (sCT) was used to capture and quantify viscous flow sintering of an additively manufactured bioactive glass scaffold in 4D. In situ sCT allowed the simultaneous quantification of individual particle (local) structural changes and the scaffold's (global) dimensional changes during the sintering cycle. Densification, calculated as change in surface area, occurred in three distinct stages, confirming classical sintering theory. Importantly, our observations show for the first time that the local and global contributions to densification are significantly different at each of these stages: local sintering dominates stages 1 and 2, while global sintering is more prevalent in stage 3. During stage 1, small particles coalesced to larger particles because of their higher driving force for viscous flow at lower temperatures, while large angular particles became less faceted (angular regions had a local small radius of curvature). A transition in the rate of sintering was then observed in which significant viscous flow occurred, resulting in large reduction of surface area, total strut volume, and interparticle porosity because the majority of the printed particles coalesced to become continuous struts (stage 2). Transition from stage 2 to stage 3 was distinctly obvious when interparticle pores became isolated and closed, while the sintering rate significantly reduced. During stage 3, at the local scale, isolated pores either became more spherical or reduced in size and disappeared depending on their initial morphology. During stage 3, sintering of the scaffolds continued at the strut level, with interstrut porosity reducing, while globally the strut diameter increased in size, suggesting overall shrinkage of the scaffold with the flow of material via the strut contacts.
This study provides novel insights into viscous flow in a complex non-idealized construct, where, locally, particles are not spherical and are of a range of sizes, leading to a random distribution of interparticle porosity, while globally, predesigned porosity between the struts exists to allow the construct to support tissue growth. This is the first time that the three stages of densification have been captured at the local and global scales simultaneously. The insights provided here should accelerate the development of 3D bioactive glass scaffolds.
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Jun 2019
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Open Access
Abstract: Biological exposures to micro- and nano-scale exogenous metal particles generated as a consequence of in-service degradation of orthopaedic prosthetics can result in severe adverse tissues reactions. However, individual reactions are highly variable and are not easily predicted, due to in part a lack of understanding of the speciation of the metal-stimuli which dictates cellular interactions and toxicity. Investigating the chemistry of implant derived metallic particles in biological tissue samples is complicated by small feature sizes, low concentrations and often a heterogeneous speciation and distribution. These challenges were addressed by developing a multi-scale two-dimensional X-ray absorption spectroscopic (XAS) mapping approach to discriminate sub-micron changes in particulate chemistry within ex-vivo tissues associated with failed CoCrMo total hip replacements (THRs). As a result, in the context of THRs, we demonstrate much greater variation in Cr chemistry within tissues compared with previous reports. Cr compounds including phosphate, hydroxide, oxide, metal and organic complexes were observed and correlated with Co and Mo distributions. This variability may help explain the lack of agreement between biological responses observed in experimental exposure models and clinical outcomes. The multi-scale 2D XAS mapping approach presents an essential tool in discriminating the chemistry in dilute biological systems where speciation heterogeneity is expected.
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Jun 2019
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[14080]
Abstract: Osteoregenerative biomaterials for the treatment of bone defects are under much development, with the aim of favouring osteointegration up to complete bone regeneration. A detailed investigation of bone-biomaterial integration is vital to understanding and predicting the ability of such materials to promote bone formation, preventing further bone damage and supporting load-bearing regions. This study aims to characterise the ex vivo micromechanics and microdamage evolution of bone-biomaterial systems at the tissue level, combining high resolution synchrotron micro-computed tomography, in situ mechanics and digital volume correlation. Results showed that the main microfailure events were localised close to or within the newly formed bone tissue, in proximity to the bone-biomaterial interface. The apparent nominal compressive load applied to the composite structures resulted in a complex loading scenario, mainly due to the higher heterogeneity but also to the different biomaterial degradation mechanisms. The full-field strain distribution allowed characterisation of microdamage initiation and progression. The findings reported in this study provide a deeper insight into bone-biomaterial integration and micromechanics in relation to the osteoregeneration achieved in vivo, for a variety of biomaterials. This could ultimately be used to improve bone tissue regeneration strategies.
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Apr 2019
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Mohamed A.
Koronfel
,
Angela E.
Goode
,
Miguel Angel
Gomez-Gonzalez
,
Johanna
Nelson Weker
,
Thiago Araujo
Simões
,
Rik
Brydson
,
Paul
Quinn
,
Michael F.
Toney
,
Alister
Hart
,
Alexandra E.
Porter
,
Mary P.
Ryan
Abstract: The unexpected high failure rates of CoCrMo hip-implants is associated with the release of a large number of inflammatory wear particles. CoCrMo is nominally a stable material, however, previous chemical speciation studies on CoCrMo wear particles obtained from periprosthetic tissue revealed only trace amounts of Co remaining despite Co being the major component of the alloy. The unexpected high levels of Co dissolution in-vivo raised significant clinical concerns particularly related to the Cr speciation in the dissolution process. At high electrochemical potentials, the alloy’s Cr-rich passive film breaks down (transpassive polarisation) facilitating alloy dissolution. The potential release of the carcinogenic Cr(VI) species in vivo has been a subject of debate. While the large scale Co dissolution observed on in vivo produced particles could indicate a highly oxidising in vivo environment, Cr(VI) species were not previously detected in periprosthetic tissue samples. However, Cr(VI) is likely to be an unstable (transient) species in biological environments and studies on periprosthetic tissue does not provide information on intermediate reaction products nor the exposure history of the wear particles. Here, an in situ spectro-microscopy approach was developed, utilising the high chemical resolution of synchrotron radiation, in order to study CoCrMo reactivity as a function of time and oxidising conditions. The results reveal limited Co dissolution from CoCrMo particles, which increases dramatically at a critical electrochemical potential. Furthermore, in-situ XAS detected only Cr(III) dissolution, even at potentials where Cr(VI) is known to be produced, suggesting that Cr(VI) species are extremely transient in simulated biological environments where the oxidation zone is small.
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Apr 2019
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[12864]
Open Access
Abstract: Previous artificial lung surrogates used hydrogels or balloon-like inflatable structures without reproducing the alveolar network or breathing action within the lung. A physiologically-accurate, air-filled lung model inspired by soft robotics is presented. The model, Soft Robotic Surrogate Lung (SRSL) is composed of clusters of artificial alveoli made of platinum-cured silicone, with internal pathways for air flow. Mechanical tests in conjunction with full-field image and volume correlation techniques characterise the SRSL behaviour. SRSLs enable both healthy and pathological lungs to be studied in idealised cases. Although simple in construction, the connected airways demonstrate clearly the importance of an inflatable network for capturing basic lung behaviour (compared to more simplified lung surrogates). The SRSL highlights the potentially damaging nature of local defects caused by occlusion or overdistension (present in conditions such as chronic obstructive pulmonary disease). The SRSL is developed as a potential upgrade to conventional surrogates used for injury risk predictions in trauma. The deformation of the SRSL is evaluated against blast trauma using a shock tube. The SRSL was compared to other conventional trauma surrogate materials and showed greatest similarity to lung tissue. The SRSL has the potential to complement conventional biomechanical studies and reduce animal use in basic biomechanics studies, where high severity protocols are used.
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Mar 2019
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I11-High Resolution Powder Diffraction
I22-Small angle scattering & Diffraction
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Mark A.
Levenstein
,
Clara
Anduix-Canto
,
Yi-Yeoun
Kim
,
Mark A.
Holden
,
Carlos
Gonzalez Nino
,
David C.
Green
,
Stephanie E.
Foster
,
Alexander N.
Kulak
,
Lata
Govada
,
Naomi E.
Chayen
,
Sarah J.
Day
,
Chiu C.
Tang
,
Britta
Weinhausen
,
Manfred
Burghammer
,
Nikil
Kapur
,
Fiona C.
Meldrum
Diamond Proposal Number(s):
[10425, 12352, 17729]
Abstract: The ability to control crystallization reactions is required in a vast range of processes including the production of functional inorganic materials and pharmaceuticals and the prevention of scale. However, it is currently limited by a lack of understanding of the mechanisms underlying crystal nucleation and growth. To address this challenge, it is necessary to carry out crystallization reactions in well‐defined environments, and ideally to perform in situ measurements. Here, a versatile microfluidic synchrotron‐based technique is presented to meet these demands. Droplet microfluidic‐coupled X‐ray diffraction (DMC‐XRD) enables the collection of time‐resolved, serial diffraction patterns from a stream of flowing droplets containing growing crystals. The droplets offer reproducible reaction environments, and radiation damage is effectively eliminated by the short residence time of each droplet in the beam. DMC‐XRD is then used to identify effective particulate nucleating agents for calcium carbonate and to study their influence on the crystallization pathway. Bioactive glasses and a model material for mineral dust are shown to significantly lower the induction time, highlighting the importance of both surface chemistry and topography on the nucleating efficiency of a surface. This technology is also extremely versatile, and could be used to study dynamic reactions with a wide range of synchrotron‐based techniques.
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Mar 2019
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[15507]
Abstract: Diffusion magnetic resonance imaging (dMRI) is considered as a useful tool to study solid tumours. However, the interpretation of dMRI signal and validation of quantitative measurements of is challenging. One way to address these challenges is by using a standard reference material that can mimic tumour cell microstructure. There is a growing interest in using hollow polymeric microspheres, mainly prepared by multiple steps, as mimics of cells in healthy and diseased tissue. The present work reports on tumour cell-mimicking materials composed of hollow microspheres for application as a standard material in dMRI. These microspheres were prepared via one-step co-electrospraying process. The shell material was poly(d,l-lactic-co-glycolic acid) (PLGA) polymers with different molecule weights and/or ratios of glycolic acid-to-lactic, while the core was polyethylene glycol (PEG) or ethylene glycol. The resultant co-electrosprayed products were characterised by optical microscopy, scanning electron microscopy (SEM) and synchrotron X-ray micro-CT. These products were found to have variable structures and morphologies, e.g. from spherical particles with/without surface hole, through beaded fibres to smooth fibres, which mainly depend on PLGA composition and core materials. Only the shell material of PLGA polymer with ester terminated, Mw 50,000–75,000 g mol−1, and lactide:glycolide 85:15 formed hollow microspheres via the co-electrospraying process using the core material of 8 wt% PEG/chloroform as the core. A water-filled test object (or phantom) was designed and constructed from samples of the material generated from co-electrosprayed PLGA microspheres and tested on a 7 T MRI scanner. The preliminary MRI results provide evidence that hollow PLGA microspheres can restrict/hinder water diffusion as cells do in tumour tissue, implying that the phantom may be suitable for use as a quantitative validation and calibration tool for dMRI.
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Mar 2019
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[7146]
Abstract: The development of extracellular matrix mimetics that imitate niche stem cell microenvironments and support cell growth for technological applications is intensely pursued. Specifically, mimetics are sought that can enact control over the self‐renewal and directed differentiation of human pluripotent stem cells (hPSCs) for clinical use. Despite considerable progress in the field, a major impediment to the clinical translation of hPSCs is the difficulty and high cost of large‐scale cell production under xeno‐free culture conditions using current matrices. Here, a bioactive, recombinant, protein‐based polymer, termed ZTFn, is presented that closely mimics human plasma fibronectin and serves as an economical, xeno‐free, biodegradable, and functionally adaptable cell substrate. The ZTFn substrate supports with high performance the propagation and long‐term self‐renewal of human embryonic stem cells while preserving their pluripotency. The ZTFn polymer can, therefore, be proposed as an efficient and affordable replacement for fibronectin in clinical grade cell culturing. Further, it can be postulated that the ZT polymer has significant engineering potential for further orthogonal functionalization in complex cell applications.
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Mar 2019
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