64 research outputs found

    Computed tomography and histological evaluation of xenogenic and biomimetic bone grafts in three-wall alveolar defects in minipigs

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    Objectives This study aimed to compare the performance of a xenograft (XG) and a biomimetic synthetic graft (SG) in three-wall alveolar defects in minipigs by means of 3D computerised tomography and histology. Materials and methods Eight minipigs were used. A total of eight defects were created in the jaw of each animal, three of which were grafted with XGs, three with SGs, and two were left empty as a negative control. The allocation of the different grafts was randomised. Four animals were euthanised at 6 weeks and four at 12 weeks. The grafted volume was then measured by spiral computed tomography to assess volume preservation. Additionally, a histological analysis was performed in undecalcified samples by backscattered scanning electron microscopy and optical microscopy after Masson’s trichrome staining. Results A linear mixed-effects model was applied considering four fixed factors (bone graft type, regeneration time, anatomic position, and maxilla/mandible) and one random factor (animal). The SG exhibited significantly larger grafted volume (19%) than the XG. The anterior sites preserved better the grafted volume than the posterior ones. Finally, regeneration time had a positive effect on the grafted volume. Histological observations revealed excellent osseointegration and osteoconductive properties for both biomaterials. Some concavities found in the spheroidal morphologies of SGs were associated with osteoclastic resorption. Conclusions Both biomaterials met the requirements for bone grafting, i.e. biocompatibility, osseointegration, and osteoconduction. Granule morphology was identified as an important factor to ensure a good volume preservation. Clinical relevance Whereas both biomaterials showed excellent osteoconduction, SGs resulted in better volume preservation.Peer ReviewedPostprint (author's final draft

    Solvent-cast direct-writing as a fabrication strategy for radiopaque stents

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    Bioresorbable stents (BRS) potential in treating coronary heart disease is still to be further developed. Current trends include research with new polymeric materials, the need for thinner struts combined with appropriate mechanical properties, radiopacity and optimized local drug delivery. This work presents a novel solvent-cast direct-write (SC-DW) printing system to manufacture BRS onto a rotating cylinder with poly-l-lactic acid (PLLA) and poly(l-lactic-co- ¿ -caprolactone) (PLCL) inks. Printed stents were characterized in terms of mechanical, thermal and biological properties with human umbilical vein endothelial cells (HUVECs). Expansion assays showed that stents withstood pressures of at least 16 atm and the indirect cytotoxicity test indicated that stents were biocompatible. Polymeric inks were further modified with the addition of 3 radiopaque agents, namely iodine, triiodobenzoic acid (TIBA) and barium sulfate (BaSO) to render stents radiopaque. Subsequent characterization showed a general increase in strut thickness with respect to control PLLA or PLCL stents, which in turn resulted in higher resistance to compression. Microcomputed tomography was used to assess stents’ radiopacity, showing that TIBA and BaSO-containing stents presented high X-ray attenuation values and maintained their radiopacity after 3 months incubation time.Peer ReviewedPostprint (published version

    Accelerated hardening of nanotextured 3D-plotted self-setting calcium phosphate inks

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    Direct ink writing (DIW) techniques open up new possibilities for the fabrication of patient-specific bone grafts. Self-setting calcium phosphate inks, which harden at low temperature, allow obtaining nanostructured scaffolds with biomimetic properties and enhanced bioactivity. However, the slow hardening kinetics hampers the translation to the clinics. Different hydrothermal treatments for the consolidation of DIW scaffolds fabricated with an a-tricalcium phosphate /pluronic F127 ink were explored, comparing them with a biomimetic treatment. Three different scaffold architectures were analysed. The hardening process, associated to the conversion of a-tricalcium phosphate to hydroxyapatite was drastically accelerated by the hydrothermal treatments, reducing the time for complete reaction from 7¿days to 30 minutes, while preserving the scaffold architectural integrity and retaining the nanostructured features. ß-tricalcium phosphate was formed as a secondary phase, and a change of morphology from plate-like to needle-like crystals in the hydroxyapatite phase was observed. The binder was largely released during the treatment. The hydrothermal treatment resulted in a 30% reduction of the compressive strength, associated to the residual presence of ß-tricalcium phosphate. Biomimetic and hydrothermally treated scaffolds supported the adhesion and proliferation of rat mesenchymal stem cells, indicating a good suitability for bone tissue engineering applications. Statement of Significance 3D plotting has opened up new perspectives in the bone regeneration field allowing the customisation of synthetic bone grafts able to fit patient-specific bone defects. Moreover, this technique allows the control of the scaffolds’ architecture and porosity. The present work introduces a new method to harden biomimetic hydroxyapatite 3D-plotted scaffolds which avoids high-temperature sintering. It has two main advantages: i) it is fast and simple, reducing the whole fabrication process from the several days required for the biomimetic processing to a few hours; and ii) it retains the nanostructured character of biomimetic hydroxyapatite and allows controlling the porosity from the nano- to the macroscale. Moreover, the good in vitro cytocompatibility results support its suitability for cell-based bone regeneration therapiesPeer ReviewedPostprint (author's final draft

    Projet ATI : Halle des matériaux

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    Le Projet halle des matĂ©riaux est un projet qui a Ă©tĂ© crĂ©Ă© cette annĂ©e spĂ©cialement pour mettre en place une procĂ©dure qualitĂ© au sein de celle-ci dans le but in fine de mettre aux normes la machine de Traction MTS 10/M ainsi que la machine de DuretĂ© REICHERTER 250 UV. La mise aux normes attendue par les encadrants est, en fait, la crĂ©ation d'un dossier qualitĂ© regroupement les documents nĂ©cessaires Ă  l'obtention de l'accrĂ©ditation. Dans le cas de la Halle des MatĂ©riaux, nous pouvions viser deux niveaux d'accrĂ©ditations plus ou moins exigeants. En effet, l'accrĂ©ditation dĂ©livrĂ©e par un laboratoire agrĂ©Ă© est rĂ©gis par des Normes d’exigence qui Ă©tablissent la qualitĂ© Ă  respecter. A l'inverse, une norme technique dĂ©finit les critĂšres Ă  respecter dans le cadre d'une manipulation par exemple. Ainsi, les 2 Normes d'exigences auxquelles nous Ă©tions confrontĂ©s Ă©taient la ISO 9001 et la ISO 17025, cette derniĂšre Ă©tant certifiĂ©e COFRAC (COmitĂ© FRançais d'ACcrĂ©ditations) elle est beaucoup plus contraignante. Nous avions commencĂ© par viser l’accrĂ©ditation selon la norme ISO 17025, cependant nous nous sommes rendu compte que les Ă©lĂšves de l’école ne pourraient plus manipuler en TP et donc nous nous sommes redirigĂ©s vers la norme ISO 9001. Nous avons fait le choix de scinder le groupe en deux pour se consacrer d'un cĂŽtĂ© sur la machine de traction et de l'autre sur la machine de duretĂ©. AprĂšs avoir analysĂ© les normes, nous nous sommes intĂ©ressĂ©s Ă  l’état des machines. Nous avons ainsi, au cours de ce projet, crĂ©Ă© la fiche de vie de chaque machine qui recense toutes les interventions qu'ont subi ces derniĂšres. Nous avons effectuĂ© un pĂ©rimĂštre sur les machines ainsi que sur de tous les appareils servants lors des manipulations (ex : extensomĂštres, pied Ă  coulisse). Le pĂ©rimĂštre est un document qui dĂ©crit avec prĂ©cision tout ce que l'objet peut faire, dans quelles conditions et quelles sont ses limites. Nous avons Ă©galement mis en place les procĂ©dures de manipulations Ă  respecter lors des essais rĂ©alisĂ©s dans le cadre d'une utilisation normalisĂ©e pour chaque machine. S'en est suivi les rapports d'essais. Au niveau de la machine de traction, la Halle des MatĂ©riaux possĂšde un extensomĂštre vidĂ©o que nous avons cherchĂ© Ă  intĂ©grer dans nos travaux. Nous avons donc dĂ» ajouter les informations concernant cette mĂ©thode d’acquisition de rĂ©sultat dans la procĂ©dure de manipulation. Concernant la machine de duretĂ©, une Ă©tude a montrĂ© qu'il Ă©tait indispensable de changer les pĂ©nĂ©trateurs pour l'obtention d'une accrĂ©ditation. Des devis ont ainsi Ă©tĂ© demandĂ©s auprĂšs de diffĂ©rents Ă©tablissements pour l’achat de nouveaux pĂ©nĂ©trateurs de mĂȘme que pour l'obtention de certificats d'Ă©talonnage. A ce jour, nous sommes en possession de devis pour l’étalonnage de chaque machine, l’achat d’un pĂ©nĂ©trateur et d’une calle Ă©talon HV5 pour la machine de duretĂ© et d’un capteur de force 5kN pour la machine de traction. Les dĂ©cisions prises par rapport Ă  ces devis se trouvent dans le compte-rendu de la rĂ©union du 18.04.2014. Les procĂ©dures terminĂ©es, nous avons pu les tester pour les rendre les plus comprĂ©hensibles possibles. Il reste bien Ă©videment des documents Ă  intĂ©grer dans notre dossier qualitĂ© tel que les calculs d'incertitudes sur les rĂ©sultats proposĂ©s aprĂšs un test, ainsi que tous les documents administratifs. Ce qui fait frein aujourd'hui Ă  toute progression du dossier est l'obtention des certificats d'Ă©talonnages sur chaque machine qui certifierait la qualitĂ© et le bon fonctionnement de celles-ci.Outgoin

    Hydrothermal processing of 3D-printed calcium phosphate scaffolds enhances bone formation in vivo: a comparison with biomimetic treatment

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    Hydrothermal (H) processes accelerate the hydrolysis reaction of a-tricalcium phosphate (a-TCP) compared to the long-established biomimetic (B) treatments. They are of special interest for patient-specific 3D-printed bone graft substitutes, where the manufacturing time represents a critical constraint. Altering the reaction conditions has implications for the physicochemical properties of the reaction product. However, the impact of the changes produced by the hydrothermal reaction on the in vivo performance was hitherto unknown. The present study compares the bone regeneration potential of 3D-printed a-TCP scaffolds hardened using these two treatments in rabbit condyle monocortical defects. Although both consolidation processes resulted in biocompatible scaffolds with osseointegrative and osteoconductive properties, the amount of newly formed bone increased by one third in the hydrothermal vs the biomimetic samples. B and H scaffolds consisted mostly of high specific surface area calcium-deficient hydroxyapatite (38 and 27 m2 g-1, respectively), with H samples containing also 10 wt.% ß-tricalcium phosphate (ß-TCP). The shrinkage produced during the consolidation process was shown to be very small in both cases, below 3%, and smaller for H than for B samples. The differences in the in vivo performance were mainly attributed to the distinct crystallisation nanostructures, which proved to have a major impact on permeability and protein adsorption capacity, using BSA as a model protein, with B samples being highly impermeable. Given the crucial role that soluble proteins play in osteogenesis, this is proposed to be a relevant factor behind the distinct in vivo performances observed for the two materials. Statement of significance The possibility to accelerate the consolidation of self-setting calcium phosphate inks through hydrothermal treatments has aroused great interest due to the associated advantages for the development of 3D-printed personalised bone scaffolds. Understanding the implications of this approach on the in vivo performance of the scaffolds is of paramount importance. This study compares, for the first time, this treatment to the long-established biomimetic setting strategy in terms of osteogenic potential in vivo in a rabbit model, and relates the results obtained to the physicochemical properties of the 3D-printed scaffolds (composition, crystallinity, nanostructure, nanoporosity) and their interaction with soluble proteins.Peer ReviewedPostprint (published version

    Regeneration of segmental defects in metatarsus of sheep with vascularized and customized 3D-printed calcium phosphate scaffolds

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    Although autografts are considered to be the gold standard treatment for reconstruction of large bone defects resulting from trauma or diseases, donor site morbidity and limited availability restrict their use. Successful bone repair also depends on sufficient vascularization and to address this challenge, novel strategies focus on the development of vascularized biomaterial scaffolds. This pilot study aimed to investigate the feasibility of regenerating large bone defects in sheep using 3D-printed customized calcium phosphate scaffolds with or without surgical vascularization. Pre-operative computed tomography scans were performed to visualize the metatarsus and vasculature and to fabricate customized scaffolds and surgical guides by 3D printing. Critical-sized segmental defects created in the mid-diaphyseal region of the metatarsus were either left empty or treated with the 3D scaffold alone or in combination with an axial vascular pedicle. Bone regeneration was evaluated 1, 2 and 3 months post-implantation. After 3 months, the untreated defect remained non-bridged while the 3D scaffold guided bone regeneration. The presence of the vascular pedicle further enhanced bone formation. Histology confirmed bone growth inside the porous 3D scaffolds with or without vascular pedicle inclusion. Taken together, this pilot study demonstrated the feasibility of precised pre-surgical planning and reconstruction of large bone defects with 3D-printed personalized scaffolds.Peer ReviewedPostprint (published version

    3D printing with star-shaped strands: a new approach to enhance in vivo bone regeneration

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    Concave surfaces have shown to promote bone regeneration in vivo. However, bone scaffolds obtained by direct ink writing, one of the most promising approaches for the fabrication of personalized bone grafts, consist mostly of convex surfaces, since they are obtained by microextrusion of cylindrical strands. By modifying the geometry of the nozzle, it is possible to print 3D structures composed of non-cylindrical strands and favor the presence of concave surfaces. In this work, we compare the in vivo performance of 3D-printed calcium phosphate scaffolds with either conventional cylindrical strands or star-shaped strands, in a rabbit femoral condyle model. Monocortical defects, drilled in contralateral positions, are randomly grafted with the two scaffold configurations, with identical composition. The samples are explanted eight weeks post-surgery and assessed by ”-CT and resin-embedded histological observations. The results reveal that the scaffolds containing star-shaped strands have better osteoconductive properties, guiding the newly formed bone faster towards the core of the scaffolds, and enhance bone regeneration, although the increase is not statistically significant (p > 0.05). This new approach represents a turning point towards the optimization of pore shape in 3D-printed bone grafts, further boosting the possibilities that direct ink writing technology offers for patient-specific applications.Peer ReviewedPostprint (published version

    Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

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    We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

    Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

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    We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO’s second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h95%0=3.47×10−25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering

    Erratum: “Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015–2017 LIGO Data” (2019, ApJ, 879, 10)

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    Due to an error at the publisher, in the published article the number of pulsars presented in the paper is incorrect in multiple places throughout the text. Specifically, "222" pulsars should be "221." Additionally, the number of pulsars for which we have EM observations that fully overlap with O1 and O2 changes from "168" to "167." Elsewhere, in the machine-readable table of Table 1 and in Table 2, the row corresponding to pulsar J0952-0607 should be excised as well. Finally, in the caption for Table 2 the number of pulsars changes from "188" to "187.
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