Sol-gel synthesis of 45S5 bioglass – Prosthetic coating by electrophoretic deposition

In this work, the 45S5 bioactive glass has been prepared by the sol-gel process using an organic acid catalyst instead of nitric acid usually used. The physico-chemical and structural characterizations confirmed and validated the elemental composition of the resulting glass. In addition, the 45S5 bioactive glass powder thus obtained was successfully used to elaborate by electrophoretic deposition a prosthetic coating on titanium alloy Ti6Al4V

Electrodeposition of biphasic calcium phosphate coatings with improved dissolution properties

Biphasic calcium phosphate coatings (hydroxyapatite/β-tricalcium phosphate) on titanium substrate (Ti6Al4V) are synthetized by pulsed current electrodeposition coupled to a thermal treatment under controlled atmosphere. The experimental conditions of the process such as the hydrogen peroxide amount and the treatment temperature are optimized in order to obtain different coatings compositions. The physico-chemical and structural characterizations of the coatings are carried out respectively by scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDXS) and X-ray diffraction (XRD). The in vitro dissolution-precipitation properties of the coated substrates are investigated by immersions into Dulbecco's Modified Eagle Medium (DMEM) from 1 to 28 days. The calcium and phosphorus concentrations variations in the biological liquid are assessed by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES) for each immersion time. Furthermore, the corrosion behavior of the coated substrates are investigated using potentiodynamic polarization tests in DMEM and in Ringer's solution. The results show that this innovative process is suitable to synthesize two coatings composed respectively of HAP (37%)/β-TCP (63%) and HAP (62%)/β-TCP (38%) with different morphologies. On the other hand, the in vitro studies reveal that the coatings composition greatly influences their behavior in physiological medium, i.e. their dissolution-precipitation and their corrosion protection properties

Nanocristallisation superficielle d'alliages de titane Ti6A14V (application au biomédical)

Ce travail présente l application et l optimisation du procédé de nanocristallisation superficielle (Surface Mechanical Attrition Treatment ou SMAT) et du procédé duplex SMAT/nitruration sur l alliage de titane Ti6A14V utilisé en chirurgie orthopédique. Le SMAT permet d améliorer les propriétés mécaniques d un matériau grâce à la formation d une couche déformée en surface composée de très petits grains. Le procédé de nitruration quant à lui, augmente la résistance à l usure d un matériau par diffusion d azote et création de nitrures à la surface d un matériau. La comparaison de la résistance à l usure du Ti6Al4V traité par différentes conditions de SMAT et de nitruration ont permis de restreindre l étude à une condition (nommée C1). Ainsi, les mesures de rugosité ont montré une diminution de la rugosité des échantillons traités par SMAT (avec et sans nitruration) ainsi qu une augmentation de la dureté en surface. Dans un deuxième temps, nous avons mis au point une méthodologie pour caractériser la microstructure des échantillons traités par SMAT C1 et traités par SMAT-nitrurés par microscopie électronique (MEB et MET). Ces études ont révélé que le traitement SMAT crée une zone déformée d environ 60 m avec des grains plus petits que dans le Ti6A14V brut, avec notamment des grains de 50 nm de diamètre en extrême surface. Lorsque le SMAT est couplé à la nitruration à basse température (375C), l épaisseur de la couche nitrurée diminue jusqu à 20 m tout en conservant des fins grains. En revanche, à haute température (730C), la microstructure du SMAT est remplacée par des gros grains et des analyses par DRX indiquent que des nitrures se sont formés. L augmentation de la dureté constatée peut être soit liée à la nanocristallisation générée par le SMAT, soit à la présence de nitrures à haute température. Enfin, des tests préliminaires de biocompatibilité indiquent que le Ti6A14V traité par SMAT reste biocompatible puisque les cellules MG 63 utilisées ont adhéré et proliféré sur les échantillons traités par SMAT. Nous avons également exploré la possibilité d améliorer la biocompatibilité du Ti6A14V en le revêtant de matériaux bioactifs comme l hydroxyapatite (HAP) ou le bio verre.This work presents the application and the optimization of the surface nanocrystallization process (Surface Mechanical Attrition Treatment or SMAT) and the duplex SMAT/nitriding process to the titanium alloy Ti6A14V used in orthopedic surgery. On the one hand, the SMAT improves the mechanical properties of a material through the formation at the surface of a deformed layer composed of very small grains. The nitriding process increases the wear resistance of a material by diffusion of nitrogen and creation of nitrides in the surface of a material. The comparison of wear resistance of Ti6A14V treated by different conditions of SMAT and nitriding has allowed us to limit our study to the condition referred to as C1. Thus, roughness measurements showed a decrease of roughness and an increase in hardness of the surface for the C1-SMAted and SMATed/nitrided samples compared to untreated Ti6A14V. In a second step, we have developed a methodology to characterize the microstructure of C1 SMATed and SMAT-nitrided samples by electron microscopy (SEM and TEM). These studies revealed that the C1 treatment created a deformed area of about 60 m thick with smaller grains than the untreated Ti6Al4V samples, in particulars with about 50 nm diameter grains in the extreme surface. When SMAT and low temperature nitriding (375 C) were combined, the thickness of the deformed layer decreased to 20 m but the small grains remained. On the contrary, at high nitriding temperatures (730 C), the microstructure of SMAT was replaced by coarse grains whilst XRD analyses indicated that nitrides formed. We assume that the improvement in hardness is either related to the nanocrystallization generated by SMAT or to the presence of nitrides at 730 C. Finally, preliminary biocompatibility tests have indicated that SMATed Ti6Al4V is biocompatible since the MG-63 cells we used adhered and proliferated on SMATed surfaces. Additionally, we have also explored the coating of Ti6A14V with bioactive materials (hydroxyapatite and bioglass) to improve its biocompatibility.REIMS-SCD-Bib. electronique (514549901) / SudocSudocFranceF

Contribution à la microanalyse X des revêtements superficiels. Application aux biomatériaux

L objet de l étude concerne la caractérisation physico-chimique des revêtements superficiels par microanalyse x et son application a l étude des revêtements prothétiques phosphocalciques. Nous avons étudies les mécanismes de formation des phosphates de calcium par electrodeposition. Nous avons vérifie les hypothèses avancées par une étude portant sur l influence de la densité de courant sur les phosphates de calcium électrodéposés. Pour caractériser ces revêtements, nous avons développé une méthodologie en microanalyse x basée sur la complémentarité de la microscopie électronique a balayage et de la microscopie électronique a balayage transmission. Par la suite, nous nous sommes intéressés aux cartographies quantitatives des films minces sur substrats. Nous avons illustre l impact de l hétérogénéité du substrat sur la quantification des films minces ; puis, nous avons présente TF_Quantif, l algorithme de quantification (concentrations et épaisseurs) que nous préconisons pour s affranchir de ces problèmes. Nous avons aussi mené une étude théorique pour déterminer les limites d application de TF_Quantif. Enfin, nous avons présenté les développements logiciels et instrumentaux nécessaires a l utilisation de TF_Quantif et nous avons effectue des profils et cartographies quantitatifs sur des films minces (de composition et d épaisseur connue) sur substrats hétérogènes ainsi que sur un revêtement de phosphate de calcium. Les résultats ont été compares avec ceux obtenus par un logiciel de quantification que nous avons développé a partir du logiciel commercial STRATAGem (SAMx, France).This work deals with electron probe microanalysis of thin films and its application to thickness and concentration determination in the case of prosthetic calcium phosphate coatings. In a first part, we have studied the formation mechanisms of calcium phosphate elaborated by electrodeposition. We carried out a methodology based on the complementarities of scanning electron microscopy and scanning transmission microscopy both associated to x-ray microanalysis. This method allowed us to verify our hypothesis about calcium phosphate formation and showed that the current density is directly connected to the kind of electrodeposited calcium phosphate. In a second part, we have carried out quantitative elemental mapping of thin film on heterogeneous substrate. Through different examples, we showed that substrate heterogeneity has a direct influence on the thin film quantification. We developed a new quantification algorithm called tf_quantif which allows us removing substrate effects during the analysis associated to a theoretical approach which determine the thickness limit of this method. Moreover, we presented the quantification software and experimental setup developed in order to use tf_quantif . Finally, we applied tf_quantif on quantitive profiles and maps on several kinds of thin films on heterogeneous substrate (including electrodeposited calcium phosphate coatings). The results were compared to those obtained from commercial software (stratagem, samx, france). We showed that our quantification algorithm gave better results in the case of thickness determination and could be successfully applied in the case of quantitative maps of thin film on heterogeneous substrate.REIMS-BU Sciences (514542101) / SudocSudocFranceF

Effects of bioactive glass particles and their ionic products on intracellular concentrations.

Numerous studies have described the bioactive properties of glass particles in the SiO(2)-CaO-Na(2)O-P(2)O(5) system. This kind of material is capable of developing a direct contact with bone through dissolution and physicochemical reactions. We have investigated the influence of bioactive particles, and ionic products from the same particles, on the intracellular concentrations in monocyte cells, which are among the first cells to colonize implantation sites. The only way to access these concentrations and particularly diffusible ionic concentrations (potassium, sodium, and chlorine) is to use cryomethods coupled to electron probe microanalysis. We have paid particular attention to the potassium:sodium ratio, the most sensitive criterion of viability. We have cultured cells with bioactive glass particles and in a conditioned medium obtained from the dissolution of the glass particles in the standard medium. Our study demonstrates that cells cultured in a conditioned medium are more active than cells cultured in a standard medium, or cells exposed to bioactive particles, and particles are more toxic for cells than are ionic products

Use of Surface Mechanical Attrition Treatment for implantable material wear enhancement

International audienceThe Co28Cr6Mo (CCM) is widely used as an articular bearing surface for artificial joints like hip and knee prostheses. Despite many advances to extend lifespan of implants, the improvement of its tribological properties is still a matter of concern. By means of SMAT (Surface Mechanical Attrition Treatment) which generates by severe plastic deformation a nanocrystalline surface layer, the mechanical, tribological, and corrosion properties of materials are enhanced. In our study, we induce a reduced grain size layer on the top surface of a CCM alloy combined with a surface hardening. As a consequence, an optimized hardness gradient up to a depth of few hundreds of microns was established. The impact of this surface modification is examined in terms of tribological properties through scratch tests and also on a dedicated multidirectional pin-on disc apparatus (multi-PoD). Working with high loads and under lubricated conditions, this equipment fulfills the standard test method for wear testing of biomaterials used in total joint prostheses. Scratch tests both with increasing and constant loads and in a multipass mode give some evidence of the benefit of SMAT. A significant decrease of wear track depth (40% in average) is actually noticed and gives some predictive information with regard to the abrasive wear strength of the treated surface. Wear tests on multi-PoD are carried out considering both parts of a conventional bearing bringing PolyEthylene in contact with CCM. A reduction of 15% of UHMWPE mass loss has been provided thanks to SMAT performed on the opponent metallic surface, the latter demonstrating much smaller scratches. Moreover, the addition of a surface mirror polishing step helps to upgrade SMAT leading to an efficient, uncontaminated surface. Finally, SMAT could be considered as an innovative approach to improve implants properties

Tribocorrosion d'alliages métalliques (acier inoxydable AISI 316L et TiAl6V) nanostructurés par procédé duplex (SMAT, Nitruration) - Projet « NANOSURF »

International audienc

Effect of surface mechanical attrition treatment on the microstructure of cobalt–chromium–molybdenum biomedical alloy

International audienc

Electrophoretic Deposition of 45S5 Bioglass® Coatings on the Ti6Al4V Prosthetic Alloy with Improved Mechanical Properties

In this paper, 45S5 Bioglass® coatings were elaborated by electrophoretic deposition (EPD) on the titanium alloy Ti6Al4V. An adequate grinding protocol was developed to obtain a stable suspension of submicrometric particles in isopropanol. The voltage and the deposition time of EPD were optimized. An optimal voltage of 30 V and two deposition times (30 and 90 s) were chosen to obtain two different coatings with thicknesses of 21 and 85 µm, respectively. The as-deposited coatings were thermally treated following a two-step protocol: one hour at 120 °C followed by one hour at 450 °C. The surface morphology and the chemical analysis of the 45S5 Bioglass® coatings were assessed, before and after heat treatment, by scanning electron microscopy associated to X-ray microanalysis (SEM-EDXS). Their structural analysis was performed by X-ray diffraction (XRD). A scratch test study was developed for mechanical properties analysis. The obtained results revealed that the obtained coatings were homogeneous, weakly crystallized with an important compactness. An increase in the critical load LC associated with the cohesive limit of the film (from Lc = 3.39 N to Lc = 5.18 N) was observed when the coating thickness was decreased from 85 to 21 µm. After the thermal treatment, the chemical composition of the coatings was not altered, and their mechanical properties were improved