Le rejet de métaux lourds dans l'environnement pose des problèmes majeurs pour les écosystèmes et la santé humaine. Parmi les solutions proposées, les techniques d'adsorption semblent particulièrement prometteuses. Ce travail de thèse visait à préparer de nouveaux matériaux à base d'hydroxyapatite afin d'améliorer les propriétés d'immobilisation de métaux lourds (Cr, Pb, Zn). Deux approches ont été explorées. La première repose sur la formation d'hydroxyapatite modifiée par les acides carboxyliques qui présentent une affinité pour le calcium de la phase minérale et pour les ions métalliques. Cette approche permet d'obtenir des matériaux hydrides organo-minéraux poreux. Sur la base des caractérisations effectuées, en particulier par DRX, RMN à l'état solide, porosimétrie d'azote et microscopie électronique, l'effet de l'incorporation des acides carboxyliques dans la structure et la chimie de surface des matériaux obtenus a été discuté. Cette discussion constitue la base de l'étude des propriétés d'adsorption des ions Pb2+ et Zn2+. La deuxième approche repose sur l'élaboration de nanocomposites associant l'hydroxyapatite et la zircone. Ce travail décrit une nouvelle voie de synthèse sol-gel de ces matériaux, conduisant l'association des deux phases permet au matériau composite de présenter une bonne affinité pour le Cr(III) et le Cr(VI).

Calcium phosphates are the most frequently used ceramics for bone regeneration due to their biocompatibility and favorable resorption properties. Their performance can however be improved if they are associated to growth factors. In order to control the release of growth factors, we have inted to synthesize calcium phosphates with controlled mesoporosity. This thesis represents the first work that combines mesoporous calcium phosphates with the growth factors TGF and VEGF. To obtain hydroxyapatite with controlled mesoporosity, we propose new synthesis pathways: the hydroxyapatite is synthesized inside the porosity of silica or carbon templates by infiltration of aqueous precursor solutions. The template is eliminated by chemical etching with NaOH (silica template) or by selective oxidation (carbon template). Six ceramics have been chosen for the analysis of their protein adsorption and release properties. First, the experimental protocol is defined using the model proteins BSA and Cytochrom C. Then, the growth factors TGF and VEGF have been used. By this study, we were able to determine which samples were the most efficient in terms of protein adsorption and release.

L'objectif de ce travail est la mise au point de filtres garnis de laitiers d'aciéries destinés au traitement du phosphore (P) des eaux usées au sein de petites installations. Deux types de laitiers on été testés: laitiers de four à arc électrique (EAF), et laitiers d'aciérie de conversion (BOF). Une approche intégrée a été suivie, avec investigations à différentes échelles: (i) Des expériences en flacons ont été réalisées pour établir les capacités de rétention du P de laitiers produits en Europe, et ainsi sélectionner les échantillons les plus adaptés pour l'élimination du P; (ii)Des expériences en colonnes ont été menées pour étudier l'effet de divers paramètres, notamment la taille et la composition du laitier, sur les performances hydrauliques et épuratoires des filtres; (iii) Enfin, des expériences sur terrain ont été conduites afin d'évaluer les performances hydrauliques et épuratoires de deux unités démonstration conçues pour le traitement du P au sein d'un marais artificiel. Les résultats expérimentaux ont indiqué que le principal mécanisme d'élimination du P est lié à la dissolution du CaO des laitiers, suivie de la précipitation de phosphate de Ca et recristallisation en hydroxyapatite (HAP). Après 100 semaines d'alimentation avec une solution de P (concentration moyenne de P totale 10,2 mgP/L), les colonnes remplies de laitiers de petite taille (BOF6-12 mm et EAF 5-16 mm) ont retenu >98% du P total en entrée, tandis que les colonnes remplies de laitiers de grande taille (BOF 20-50 mm et EAF 20-40) ont retenu 56et 86% du P total en entrée, respectivement. Il apparaît que, plus la taille des laitiers est petite, plus la surface spécifique disponible pour la dissolution du CaO et pour l'adsorption des phosphates de Ca est grande. Les expériences sur terrain ont confirmé que les laitiers sont efficaces pour le traitement du P de l'effluent d'un marais artificiel (concentration moyenne du P totale 8,3 mg P/L). Sur une période de 85 semaines d'opération, de laitiers EAF ont retenu le 36% du P total en entrée, tandis que les laitiers BOF ont retenu le 59% du P total en entrée.L'efficacité de rétention du P apparaît augmenter avec la température et le temps de rétention hydraulique (HRT),très probablement parce que l'augmentation de la température et du HRT a favorisé la dissolution de la CaO et la précipitation de phosphate de Ca. Toutefois, il a été constaté que HRT >3 jours peuvent produire des pH élevés (>9), à la suite d'une excessive dissolution de CaO.Cependant, les résultats des unités démonstration ont montré que, à HRT de 1-2 jours, les filtres produisent des pH élevés seulement pendant les 5 premières semaines de fonctionnement, puis les pH se stabilisent en dessous de 9. Enfin, une équation de dimensionnement sur la base des résultats expérimentaux a été proposée.

The main goal of this research is to construct hierarchical microstructures from polymer nanocomposites. Specifically, the research focused on constructing tensegrity-inspired microstructure where the nanoparticles are the compression members and the polymer matrix is tensile web. In order to achieve the tensegrity-inpired microstruture, the research was conducted with the following objectives. 1. Synthesis of Hydroxyapatite (HAp) nanoparticles of controlled shapes using block copolymer templates. 2. Investigation of the effects of particle loadings and shapes on isotropic nanocomposite properties. 3. Construction of HAp building blocks into the tensegrity-inspired microstructures First, in order to use the nanoparticles for this structure, needle-shaped HAp nanoparticles were synthesized using block copolymer templates. The results indicated that significant amount of polymer remained on particle surface. Since these particles were coated with polymer blocks, the decorated polymer blocks were considered as the interphase material which would be used to prestress the HAp nanoparticles, and the particles would be acted as the building blocks for constructing tensegrity-inspired microstructure. For nanocomposites, polymer coating on HAp nanoparticles promoted particle dispersion. The effect of particle shapes on thermomechanical properties did not show significant differences between the two particle systems due to their low aspect ratios and chemical similarity. However, the polymer crystallinity and crystallization showed different trend as a function of particle loadings in two particle systems, and the behavior was unified through a common particle spacing of approximately 120 nm. In order to investigate the effect of particle arrangement in the polymer matrix, needle-shaped HAp nanoparticles synthesized with two different block copolymers were mixed with different morphology of polymer matrices and manipulated particle arrangement using the drawing process. Nanocomposites prepared with different matrix morphologies showed the similar dispersion characteristics and reinforcement behavior. The experimental results showed the drawing process influenced the particle arrangement in the polymer matrix, and the particle arrangement and reinforcement behavior were influenced by polymer matrix morphology. The thermomechanical properties of both matrix systems enhanced through the drawing process in the glassy region, but the effect of degree of particle orientation was difficult to distinguish due to low aspect ratios of HAp particles which was not enough to impact on overall microstructure.

The design of an uncemented hip arthroplasty implant affects its long-term survival. Characteristics such as the form and the finish of the implant are crucial in order to achieve the best possible conditions for long-term implant survival. In this thesis we hypothesized that different shapes of stems and cups used in primary and revision total hip arthroplasty (THA), and their finish with hydroxyapatite (HA) coating affect implant stability and thus long-term survival. In 2 prospective cohort studies the clinical outcome, the stability measured with radiostereometric analysis (RSA), and the periprosthetic changes in bone mineral density (BMD) measured with dual-energy x-ray absorptiometry (DXA) were investigated in 2 uncemented THA implants – the CFP stem and the TOP cup. In 3 register studies the effect of HA coating on uncemented THA implants used in primary and revision arthroplasty was investigated. Both implants investigated in the prospective cohort studies showed an excellent short-term clinical outcome with good primary stability, but neither their novel form nor the finish with HA protected the implants from the proximal periprosthetic demineralization that usually occurs around other uncemented THA implants. The register studies revealed that HA coating on cups used in primary and revision THA is a risk factor for subsequent revision of the implant. The use of HA coating on the stem in primary THA did not affect long-term survival. Additionally, the shape of an implant plays a crucial role for implant stability and survival. In conclusion, this thesis highlights that the finish of implants with HA coating does not prevent periprosthetic proximal femoral bone loss and can even enhance the risk of revision of both primary and secondary cups. Importantly, the shape of uncemented THA implants affect their stability, showing that the implant form is a crucial factor for the long-term survival.

La presente tesis doctoral (i.e., “New developments in calcium phosphate bone cements: approaching spinal applications”) aporta nuevos conocimientos en el campo de los cementos óseos de fosfato de calcio (CPBCs) en relación a su aplicación clínica en el campo de la cirugía vertebral mínimamente invasiva. La hipótesis central de esta investigación fue formulada en los siguientes términos: “Los cementos apatíticos pueden ser (si se optimizan) una alternativa mejor (debido a sus propiedades de fraguado, endurecimiento y bioactividad) a los actuales cementos poliméricos utilizados en vertebroplastia y cifoplastia”. En este sentido, la presente tesis doctoral ha investigado nuevas soluciones para obtener cementos apatíticos con: (a) mejores propiedades mecánicas (Cap. 2); (b) capacidad para desarrollar macroporosidad abierta e interconectada (Cap. 3); (c) mejor estabilidad y reactividad química (Cap. 4 & 5); (d) óptimas propiedades de biocompatibilidad y osteogénicas (Cap. 6, 7 & 8); y (e) mejores propiedades de inyectabilidad (Cap. 7). Además, en esta tesis se ha investigado la aplicación de los ultrasonidos a la monitorización del fraguado inicial de cementos de base cerámica con el objetivo de relacionar la evolución de las propiedades acústicas con las características de inyectabilidad de estos cementos (Cap. 9 &10). El Capítulo 2 muestra que las propiedades mecánicas, de trabajabilidad y de fluidez de los cementos apatiticos pueden mejorarse con la adición de superplastificantes en la fase líquida de los cementos. Los resultados muestran que estos aditivos pueden mejorar la inyectabilidad inicial de los cementos sin afectar a su resistencia mecánica final. El Capítulo 3 muestra que la adición de cristales de sulfato de calcio dihidratado (CSD) a la fase en polvo de un cemento de base alfa-fosfato tricálcico (α-TCP) puede modular la formación de macroporosidad durante su fraguado. Las propiedades resultantes del fraguado de estos nuevos cementos bifásicos son debidas a la disolución del α-TCP y a la precipitación de una matriz de cristales entrecruzados de hidroxiapatita deficiente en calcio (CDHA) que contiene porosidad homogéneamente distribuida gracias a la disolución pasiva de la fase de CSD. Estos cementos bifásicos mostraron resistencias mecánicas adecuadas para la aplicación en hueso trabecular. El Capítulo 4 trata sobre la problemática del proceso de fabricación de la fase reactiva principal de los cementos apatíticos, i.e. del α-TCP (α- Ca3(PO4)2). Los resultados muestran que si la relación calcio-fosforo (Ca/P) de la mezcla reactiva inicial se desvía de la relación estequiométrica Ca/P=1.50 entonces los cementos resultantes poseen malas propiedades de fraguado y de endurecimiento. Estas desviaciones ocurren fácilmente durante el proceso de sinterización del α-TCP cuando los reactivos de mezcla utilizados varían su pureza de un lote a otro. En estos casos el α- TCP obtenido produce cementos no-reactivos, i.e. que no fraguan ni endurecen. El Capítulo 5 plantea nuevas soluciones para controlar y mejorar la reactividad química del α-TCP. En este sentido, se han estudiado nuevas soluciones sólidas sinterizadas del tipo (3.CaO-1.P2O5)1-x(FeO)x con el objetivo de reemplazar al reactivo α-TCP en las actuales formulaciones de CPBCs. Los resultados muestran que la modificación del α-TCP con hierro permite recuperar la reactividad química de cementos no-reactivos de base α-TCP con una mejora adicional de las propiedades de fraguado y reológicas de los cementos resultantes. El Capítulo 6 centra su atención sobre la citocompatibilidad de las nuevas formulaciones de cementos (investigadas en los Caps. 3-5). Los resultados mostraron que los nuevos cementos de fosfato de calcio modificados con hierro (IM-CPCs) poseen características apropiadas de citocompatibilidad ya que la adhesión y la viabilidad celular no fueron afectadas con el tiempo de cultivo por la concentración de hierro. El Capítulo 7 hace referencia a nuevas aproximaciones para mejorar la inyectabilidad de los cementos óseos de base α-TCP. Los resultados demostraron que la adición de nanopartículas de óxido de hierro en la fase en polvo de un cemento de base α-TCP mejora la inyectabilidad inicial y también la resistencia máxima a compresión del cemento sin afectar a sus reacciones físico-químicas de fraguado ni a su citocompatibilidad. El Capítulo 8 se centra sobre el carácter de citocompatibilidad, biocompatibilidad y osteogénico de los nuevos cementos bifásicos porosos/modificados con hierro (estudiados en los Caps. 3-7). Los resultados demostraron que los cementos bifásicos formulados a base de CSD y α-TCP modificado con hierro poseen la habilidad de favorecer la colonización celular in vitro y proporcionan aposición ósea firme in vivo. Se concluye que estas nuevas formulaciones tienen características de cito- y biocompatibilidad de interés como biomaterial para la sustitución/reconstrucción del tejido óseo esponjoso en aplicaciones de cirugía vertebral tales como la vertebroplastia o la cifoplastia. En el Capítulo 9 y en el Capítulo 10 se aproximan los ultrasonidos como una técnica fiable para caracterizar las propiedades iniciales de fraguado de materiales de tipo cemento. Esta técnica no-destructiva permite monitorizar el fraguado del cemento en su totalidad. Los resultados obtenidos relacionan las propiedades acústicas y de material con factores experimentales del proceso de fabricación y con características reológicas. Se concluye que la monitorización ultrasónica del fraguado de cementos óseos puede contribuir a establecer protocolos prácticos adecuados para su inyección mediante técnicas de cirugía mínimamente invasivas en cirugía vertebral. Finalmente, el Capítulo 11 presenta un resumen de los resultados más relevantes de esta investigación. / This thesis is aimed at contributing to close the gap between the research conducted on the field of calcium phosphate bone cements (CPBCs) and their specific spinal clinical use. The main working hypothesis was formulated as follows: “Apatitic cements could be (after further optimization) an alternative or better option (due to its natural setting, hardening and bioactive properties) to the present use of polymeric cements in vertebroplasty and kyphoplasty”. In this regard, this thesis has approached new solutions to obtain apatitic bone cements (ABCs) with: (a) improved mechanical properties (Chapter 2); (b) the ability to develop open-interconnected macroporosity (Chapter 3); (c) improved chemical reactivity and stability (Chapter 4 & 5); (d) suitable biocompatible and osteogenic properties (Chapter 6, 7 & 8); and (e) improved injectability properties (Chapter 7). Moreover, this thesis has also approached ultrasound in order to monitor the early setting stages of ceramic based bone cements to link acoustic and material properties with some intrinsic cement-injectability features (Chapter 9 & 10). Chapter 2 showed that workability, flowing and mechanical properties of ABCs can be improved by adding superplasticizers to the liquid cement phase. The results indicated that superplasticizers can be used to improve the injectability and the strength of apatitic bone cements. Chapter 3 showed that calcium sulfate dihydrate (CSD) crystals can be added into the cement powder phase to modulate the macroporosity of the cement during its setting. This was proved with an alpha-tricalcium phosphate (α-TCP) bone cement. The setting properties of the new biphasic cements resulted from the progressive dissolution-precipitation of α-TCP into calcium-deficient hydroxyapatite (CDHA) crystals and the passive dissolution of the CSD phase, which render porosity homogeneously distributed into an entangled matrix of CDHA crystals. The biphasic cements showed suitable strength for trabecular bone applications. Chapter 4 focused the manufacturing process of α-TCP (α-Ca3(PO4)2), the main cement reactant of most commercial ABCs. It has been shown that if calcium-to-phosphorous (Ca/P) ratio deviated from Ca/P=1.50, the resulting cements had worse setting and hardening properties. These deviations can result from sintering if reactives are not pure from batch to batch; in this case the α-TCP shows no-cement reactivity at all. Chapter 5 approached new solutions to control and improve the chemical reactivity of the α-TCP phase. In this sense, new solid solutions like (3.CaO-1.P2O5)1-x(FeO)x were investigated to replace the α-TCP of the present CPBCs. The results showed that iron modification of α-TCP recovered the chemical reactivity of unreactive α-TCP cements with even better setting and rheological end-cement properties. Chapter 6 focused the attention into the cytocompatibility of the new cement formulations (investigated previously; chapters 3-5). It is showed that the new iron-modified calcium phosphate cements (IM-CPCs) have cytocompatible features (i.e. cells’ adhesion and viability were not affected with culturing time by the iron concentration dose). Chapter 7 concerned a new approach to improve the injectability of α-TCP based bone cements. It has been shown that the addition of iron oxide nanoparticles into the powder phase of α-TCP based cement improved both, the initial injectability and maximum compressive strength of the cement without affecting their physico-chemical setting reactions and their cytocompatibility. Chapter 8 pointed to the cytocompatibility, the biocompatibility and the osteogenic character of new biphasic porous/iron-modified cements (investigated previously; chapters 3-7). The results showed that biphasic cements made of CSD and iron-modified α-TCP had the ability to support cellular colonization in vitro and lead firm bone binding in vivo. It is concluded that these new formulations has cyto- and biocompatible features of interest as further cancellous bone replacement biomaterial for spinal surgery applications such as vertebroplasty or kyphoplasty. Chapter 9 & 10 approached ultrasound as more reliable characterisation technique of the early setting properties of bone cement-like materials than the Gillmore needles standard. This non-destructive technique allowed monitoring the whole setting period of experimental calcium sulphate and calcium phosphate bone cements. The results linked acoustic and material properties with the experimental factors studied and with cement flowing features. It is expected that, after further optimization, ultrasound monitoring should help, in combination with recent approaches that measure certain injectability characteristic for calcium-based bone cements (CBC’s), to set up good practice protocols for CBC’s injection during minimally invasive surgery. Finally, Chapter 11 presents a summary of the major findings of this thesis.

Apatite group of minerals have been widely used in applications like detoxification of wastes, disposal of nuclear wastes and energy applications in addition to biomedical applications like bone repair, substitution, and coatings for metal implants due to its resemblance to the mineral part of the bone and teeth. X-ray diffraction patterns of bone are similar to mineral apatites such as hydroxyapatite and fluorapatite. Formation and physicochemical properties of apatites can be understood better by computer modeling. For this reason, lattice parameters of possible apatite compounds (A10(BO4)6C2), constituted by A: Na+, Ca2+, Ba2+, Cd2+, Pb2+, Sr2+, Mn2+, Zn2+, Eu2+, Nd3+, La3+, Y3+ / B: As+5, Cr+5, P5+, V5+, Si+4 / and C: F-, Cl-, OH-, Br-1 were predicted from their elemental ionic radii by artificial neural networks techniques. Using artificial neural network techniques, prediction models of lattice parameters a, c and hexagonal lattice volumes were developed. Various learning methods, neuron numbers and activation functions were used to predict lattice parameters of apatites. Best results were obtained with Bayesian regularization method with four neurons in the hidden layer with &lsquo / tansig&rsquo / activation function and one neuron in the output layer with &lsquo / purelin&rsquo / function. Accuracy of prediction was higher than 98% for the training dataset and average errors for outputs were less than 1% for dataset with multiple substitutions and different ionic charges at each site. Non-stoichiometric apatites were predicted with decreased accuracy. Formulas were derived by using ionic radii of apatites for lattice parameters a and c.

In this study, it was aimed to investigate the structural, mechanical and biological properties of nano hydroxyapatite (HA) doped with yttrium and fluoride with different compositions. HAs were synthesized by precipitation method. After sintering at 900oC, 1100oC or 1300oC for 1 hour, the structural properties of HAs were investigated by XRD, FTIR spectroscopy and SEM. High relative densities (above 88 % of relative density) were achieved after sintering. No second phases were observed in XRD measurements. Hexagonal lattice parameters and unit cell volumes of doped HAs decreased indicating the substitutions of ions. Characteristics absorbtion bands of HA and additional bands due to fluoride substitutions were observed in FTIR patterns. SEM images showed that grain sizes decreased with increasing doping amounts and decreasing sintering temperatures. Discs prepared by cold pressing were sintered at 900oC, 1100oC and 1300oC for 1 hour to determine mechanical properties. Mechanical properties of HAs were found to be directly related to the sintering temperatures and amount of dopings. Biocompatibility of pure and doped HA discs was assessed with in vitro cytotoxicity studies. Cell attachment, proliferation and differentiation state of cells were studied using MTT, ALP and calcium assays and SEM. Cell attachment and proliferation were enhanced with dopings and increasing sintering temperatures. The highest ALP production and calcium deposition were observed on HAs sintered at 1100oC. In vitro studies revealed that 1100oC was the sintering temperature for best cell responses. Specifically, 2.5YFHA seemed to be promising as an alternative for pure HA among all doped HAs.

Hard tissue engineering holds the promise of restoring the function of failed hard tissues and involves growing specific cells on extracellular matrix (ECM) to develop &bdquo / &bdquo / tissue-like&rdquo / structures or organoids. Chitosan is a linear amino polysaccharide that can provide a convenient physical and biological environment in tissue regeneration attempt. To improve chitosan&amp / #8223 / s mechanical and biological properties, it was blended with another polymer gelatin. 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) were used to crosslink the chitosan-gelatin matrix to produce stable structures. These natural polymers are mechanically weak especially to serve as a bone substitude and therefore, an inorganic calcium phosphate ceramic, hydroxyapatite, was incorporated to improve this aspect. The objective of this study was to develop chitosan-gelatin/hydroxyapatite scaffolds for a successful hard tissue engineering approach. For this reason, two types of hydroxyapatite, as-precipitated non-sintered (nsHA) and highly crystalline sintered (sHA) were synthesized and blended into mixtures of chitosan (C) and gelatin (G) v to produce 2-D (film) and 3-D (sponge) structures. The physicochemical properties of the structures were evaluated by scanning electron microscopy, X-Ray Diffraction (XRD), Fourier Transform Infrared-Attenuated Total Reflectance spectrometer (FTIR-ATR), differential scanning calorimetry, contact angle and surface free energy measurements and swelling tests. Mechanical properties were determined through tensile and compression tests. In vitro cell affinity studies were carried out with SaOs-2 cells. MTS assays were carried out to study cell attachment and proliferation on the 2-D and 3-D scaffolds. Several methods such as confocal, fluorescence and scanning electron microscopy were used to examine the cell response towards the scaffolds. Cell affinities of the samples were observed to change with changing chitosan-gelatin ratio and hydroxyapatite addition into the matrices. XRD and FTIR results confirmed the purity of the hydroxyapatite synthesized. Mechanical test results showed that 2-D and 3-D chitosan-gelatin/hydroxyapatite constructs have similar properties as bones, and in vitro studies demonstrated that the prepared matrices have the potential to serve as scaffold materials in hard tissue engineering applications.

Long bone fractures are fixed with bone plates to restrain movement of bone fragments. Fracture site must experience some pressure for proper healing. Bone plates are mostly made up of metals having 5 - 10 times higher elastic modulus than bones and most of the load is carried by them, leading to stress shielding and a bony tissue with low mineral density and strength. To avoid these problems, biodegradable polymer-based composite plates were designed and tested in this study. Poly(L-lactide) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biodegradable polymer composite fibers containing hydroxyapatite (HAP) nanoparticles were produced by extrusion and spinning techniques to reinforce the polymeric bone plates. The composite fibers were expected to mimic the natural organization of bone so that HAP nanorods aligned parallel to the loading axis of bone plate. Also, lactic acid was grafted on HAP surfaces and had a positive effect on the mechanical properties of the PLLA composites. A 50% (w/w) HAP nanoparticle content was found to increase tensile modulus value (4.12 GPa) ca. 2.35 times compared to the pure polymeric fiber with a reduction to one third of the original UTS (to 50.4 MPa). The fibers prepared were introduced to polymeric plates with their long axes parallel. Fiber reinforced bone plates were compression tested longitudinally and up to a 4% increase in the Young&rsquo / s Modulus was observed. Although this increase was not high was not high probably due to the low fiber content in the final plates, this approach was found to be promising for the production of biodegradable polymeric bone plates with mechanical values closer to that of cortical bones. Biological compatibility of fibers was validated with in vitro testing. The osteoblasts attached and spread on the fibers indicating that bone fractures fixed with these could attract of bone forming osteoblasts into defect area and help speed up healing.