STEM and EDXS characterisation of physico-chemical reactions at the periphery of sol-gel derived Zn-substituted hydroxyapatites during interactions with biological fluids

With its good properties of biocompatibility and bioactivity hydroxyapatite (HA) is highly used as bone substitutes and as coatings on metallic prostheses. In order to improve bioactive properties of HA we have elaborated Zn2+ doped hydroxyapatite. Zn2+ ions substitute for Ca2+ cations in the HA structure and four Zn concentrations (Zn/Zn+Ca) were prepared 0.5, 1, 2, 5 % at. To study physico-chemical reactions at the materials periphery, we immersed the bioceramics into biological fluids for delays from 1 day to 20 days. The surface changes were studied at the nanometer scale by scanning transmission electron microscopy associated to energy dispersive X-ray spectroscopy. After 20 days of immersion we observed the formation of a calcium-phosphate layer at the periphery of the HA doped with 5% of zinc. This layer contains magnesium and its thickness was around 200 nm. Formation of this Ca-P-Mg layer represents bioactivity properties of the 5% Zn-substituted hydroxyapatite. This biologically active layer improves properties of HA and will permit a chemical bond between the ceramic and bone

Mise en oeuvre de méthodes nucléaires et de diffraction pour l'analyse de la structure de l'hydroxyapatite dopée et des transferts d'éléments métalliques à partir de biomateriaux implantés in vivo

The metallic prostheses coated or not by biomaterials are widely used in orthopaedic surgery. The becoming of these implants are studied, particularly the degradation which can induce metallic elements transfer in adjacent tissues. The synthetic hydroxyapatite, used as filled biomaterials, resorbe fastly when it is doped with zinc as pure HAP or doped with manganese. The improve is due to biology or physico­chemistry factor. Analyses by neutron activation, ICP/AES, X­ray diffraction and infrared spectroscopy have been realised and show that these hydroxyapatites have the same composition and the same structure as pure apatite. The location of zinc in the crystalline structure of apatite has been determine by EXAFS (Extended X­ray Fine Structrure). The association of these results shows that the addition of zinc in the apatite induces a local deformation of the structure that may allow the release of this element in the organism and favours the resorption of the hydroxyapatite. Despite the progress, all metallic prostheses implant in organism induce corrosion or exchange with tissue that can produce a loosening of the prostheses. The biomaterials used to fix the implant do not stop the migration of the metallic element toward adjacent tissues. Post­mortem and surgical tissues taken off around implants were studied by PIXE (Particle Induced X­ray Emission) in order to locate and evaluate qualitatively and quantitatively the contamination with an analytical method that we have developed. The analysis by transmission electronic microscopy (TEM) shows the nature and the form of the released element. Used of nuclear and diffraction method to analyse the structure of the hydroxyapatite doped with zinc and the transfer of metallic element released by biomaterials implanted ``in vivo''.Les prothèses métalliques recouvertes ou non de biomatériaux sont largement utilisées en chirurgie orthopédique. Le devenir de ces implants a été étudié et en particulier la dégradation qui peut induire le transfert d'éléments métalliques dans les tissus adjacents. L'hydroxyapatite synthétique, utilisée en tant que matériau de comblement, se résorbe plus vite lorsqu'elle est dopée en zinc que l'HAP pure ou dopée au manganèse. Les causes de cette amélioration sont d'origine biologique et physico­chimique. Les analyses par activation neutronique, spectrométrie d'émission à source de plasma (ICP/AES), diffraction de rayons X et spectrométrie infrarouge ont été effectuée et ont montré que ces hydroxyapatites avaient des compositions et une structure semblables à celles des apatites pures. La localisation du zinc dans la structure cristalline de l'HAP a été déterminée par EXAFS (Extended X­ray Fine Structure). L'association de ces résultats montre que l'addition du zinc dans l'apatite entraîne une déformation locale de la structure ce qui pourrait permettre un relargage éventuel de cet élément dans l'organisme et favoriserait ainsi la résorption de l'hydroxyapatite. Malgré les progrès réalisés, tout implant métallique mis en place dans un corps humain est le siège d'une corrosion ou d'échange avec le tissu vivant pouvant entraîner à terme un descellement de prothèse. Les matériaux de fixation utilisés ne permettent pas d'arrêter la migration des éléments métalliques vers les tissus, ce qui a pour conséquence une contamination des tissus adjacents. Les tissus post­mortem et per­opératoires prélevés autour d'implants sont étudiés par la méthode d'analyse PIXE (Particle Induced X­ray Emission) afin de localiser et d'évaluer qualitativement et quantitativement la contamination à l'aide d'une méthode d'analyse que nous avons développée. Parallèlement, la microscopie électronique à transmission (TEM) a montré la forme sous laquelle ces éléments ont été relargués

MISE EN UVRE DE METHODES NUCLEAIRES ET DE DIFFRACTION POUR L'ANALYSE DE LA STRUCTURE DE L'HYDROXYAPATITE DOPEE ET DES TRANSFERTS D'ELEMENTS METALLIQUES A PARTIR DE BIOMATERIAUX IMPLANTES IN VIVO

CLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

Preparation of ordered mesoporous and macroporous thermoplastic polyurethane surfaces for potential medical applications

International audienceThermoplastic polyurethanes are widely used in medical devices. In order to limit some of their shortfalls, like microbial attachment, surfaces modifications can be required. In this work, a two-step replication method was used to create ordered macroporous and mesoporous thermoplastic polyurethane surfaces using anodic aluminum oxide as master template. The intermediate mould materials that were tested were polystyrene and a polyacrylate resin with inorganic filler. All obtained surfaces were characterized by scanning electron microscopy. The initial anodic aluminum oxide surfaces possessed macro or mesopores, function of anodization conditions. The intermediate mould structure correctly replicated the pattern, but the polystyrene surface structures (pillars) were less resistant than the polyacrylate resin ones. The thermoplastic polyurethane pattern possessed macropores or mesopores of about 130 nm or 46 nm diameter and of about 300 nm or 99 nm interpore distances, respectively, in accordance with the initial pattern. Thermoplastic polyurethanes pore depth was however less than initial anodic aluminum oxide pore depth, linked to an incomplete replication during intermediate mould preparation (60 to 90% depth replication). The correct replication of the original pattern confirms that this novel fabrication method is a promising route for surface patterning of thermoplastic polyurethanes that could be used for medical applications

Anodic alumina oxide surfaces prepared by dual hard and mild anodization at subzero temperature: Surface microscopic characterization and influence on wettability

International audienceMultistage anodizations allow the preparation of new generations of ordered anodic alumina oxide porous structures with large interpore distances, yet the influence of second anodization and pore widening times on pore dimensions and wettability of the obtained structures has not yet been fully studied. The main objective of this study was to characterize the obtained pores (dimensions and morphology), for different anodizations and pore widening times, and to investigate their respective influence on surface wettability. Anodic alumina oxide ordered porous surfaces were prepared using a dual hard and mild anodization process with oxalic and phosphoric acids at subzero temperature, with or without pore widening. Statistical analyses were realized on pore measurements from samples produced with a large range of anodization durations (7 different tested times). The obtained surfaces possessed regular ordered pores of 99 nm and 307 nm for respectively median pore diameter and inter-pore distance, before pore widening, and did not conform to expected theoretical values for either usual lone mild or hard anodization conditions. The slow growth of pore depth (median of 11 nm/min) observed during second anodization could be explained by the subzero electrolyte temperature used. Pore widening effectively increased pore diameter, but had statistically a bigger impact on diameters for shorter second anodization time than for longer ones. Also, pore widening significantly decreased pore depth as well as the oxide barrier thickness. Additionally, porosity increased from 9.57% to 14.8% after 3 hours of pore widening, but did not significantly affect surface wettability, which was however increased when compared to flat control surfaces. The obtained results showed that a dual anodization with different electrolytes at a subzero temperature had a significant impact on pores dimensions. A discussion on the respective effects of surface chemistry and surface roughness in the wetting evolution was proposed. Previous article in issu

An integrated Bayesian modeling approach for the growth of Indian Ocean yellowfin tuna

The Indian Ocean Tuna Tagging Program provided a unique opportunity to collect demographic data on the key commercially targeted tropical tuna species in the Indian Ocean. In this paper, we focused on estimating growth rates for one of these species, yellowfin (Thunnus albacares). Whilst most growth studies only draw on one data source, in this study we use a range of data sources: individual growth rates derived from yellowfin that were tagged and recaptured, direct age estimates obtained through otolith readings, and length-frequency data collected from the purse seine fishery between 2000 and 2010. To combine these data sources, we used an integrated Bayesian model that allowed us to account for the process and measurement errors associated with each data set. Our results indicate that the gradual addition of each data type improved the model's parameter estimations. The Bayesian framework was useful, as it allowed us to account for uncertainties associated with age estimates and to provide additional information on some parameters (e.g., asymptotic length). Our results support the existence of a complex growth pattern for Indian Ocean yellowfin, with two distinct growth phases between the immature and mature life stages. Such complex growth patterns, however, require additional information on absolute age of fish and transition rates between growth stanzas. This type of information is not available from the data. We suggest that bioenergetic models may address this current data gap. This modeling approach explicitly considers the allocation of metabolic energy in tuna and may offer a way to understand the underlying mechanisms that drive the observed growth patterns

IO Tuna tagging

The Indian Ocean Tuna Tagging Program (IOTTP) provided a unique opportunity to assess the viability of estimating the age of tropical tunas from the micro-structural features of otoliths. Here, we analyzed the length measurements and micro-increment counts collected for 506 sagittal otoliths, of which 343 were chemically marked with oxytetracycline, for bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis), and yellowfin tuna (Thunnus albacares). Our results show that the otoliths of tropical tunas grow more slowly than the rest of the body. Our findings confirm that both yellowfin and juvenile bigeye deposit daily increments in their otoliths, though ages are underestimated for large bigeye (>100 cm) when derived from micro-increment counts. Our results also indicate that skipjack otoliths are not suitable for age estimations during the adult phase, as evidenced by the poor agreement between micro-increment counts and days-at-liberty. We hypothesize that the income breeding strategy of skipjack could explain the variability observed in the deposition rates. Due to their complex micro-structural patterns, the reading of tropical tuna otoliths requires a degree of interpretation that can result in poor count precision and large variability in micro-increment counts, both among and within teams of readers. Age estimates were found to vary between readers, a factor which can eventually affect growth estimates and ultimately, impact on fisheries management decisions and outcomes. To address this, we recommend that reference collections of otoliths are developed, with a view to standardizing the reading process. Further, alternative methods, such as annual age estimations (as opposed to daily), and alternative structures, such as dorsal spines for skipjack, should be used to improve the accuracy of age estimations and the speed with which they can be made

One-pot Synthesis of TiO2 Nanoparticles in Suspensions for Quantification of Titanium Debris Release in Biological Liquids

International audienceIn this work we have developed an analytical method to measure potential titanium debris released from TiO 2 nanotube layers devices immersed in biological fluids. This quantitative study is highly required to ensure both the security and non toxicity of the nanostructured surfaces used as future implantable medical devices in the living. A one-pot synthesis process is developed to produce high quality standard solutions of titanium dioxide nanoparticles in aqueous medium. The elaborated dispersion is then used to fabricate standard solutions in both aqueous and human blood plasma media. The synthesized nanoparticles dispersion was characterized by granulometry. The nanoparticles structure and morphology were then observed using Transmission Electron Microscopy (TEM). Thermogravimetric Analysis (TGA) was used to evaluate the concentration of TiO 2 in the suspension. A quantitative routine by the use of Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) is developed. The quantification threshold of titanium species is found to be in the 30-40 ppb range. None interference is detected between the particles and the human blood plasma. Using the established quantitative routine, the titanium species release from titania nanotube layers in human blood plasma is evaluated

Determining the age of tropical tunas in the Indian Ocean from otolith microstructures

The Indian Ocean Tuna Tagging Program (IOTTP) provided a unique opportunity to assess the viability of estimating the age of tropical tunas from the micro-structural features of otoliths. Here, we analyzed the length measurements and micro-increment counts collected for 506 sagittal otoliths, of which 343 were chemically marked with oxytetracycline, for bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis), and yellowfin tuna (Thunnus albacares). Our results show that the otoliths of tropical tunas grow more slowly than the rest of the body. Our findings confirm that both yellowfin and juvenile bigeye deposit daily increments in their otoliths, though ages are underestimated for large bigeye (>100 cm) when derived from micro-increment counts. Our results also indicate that skipjack otoliths are not suitable for age estimations during the adult phase, as evidenced by the poor agreement between micro-increment counts and days-at-liberty. We hypothesize that the income breeding strategy of skipjack could explain the variability observed in the deposition rates. Due to their complex micro-structural patterns, the reading of tropical tuna otoliths requires a degree of interpretation that can result in poor count precision and large variability in micro-increment counts, both among and within teams of readers. Age estimates were found to vary between readers, a factor which can eventually affect growth estimates and ultimately, impact on fisheries management decisions and outcomes. To address this, we recommend that reference collections of otoliths are developed, with a view to standardizing the reading process. Further, alternative methods, such as annual age estimations (as opposed to daily), and alternative structures, such as dorsal spines for skipjack, should be used to improve the accuracy of age estimations and the speed with which they can be made