Dissertations / Theses on the topic 'Hydroxyapatite'

Des biocéramiques d’hydroxyapatite silicatée (SiHA) macro-micro-poreuses et d’architecture contrôlée ont été mises en forme par microstéréolithographie puis consolidées par frittage. Dans cette optique, des suspensions de particules SiHA, dispersées en milieu organique photoréactif, ont été développées. Leur comportement rhéologique a été étudié en fonction des taux de poudre, de diluant organique et de dispersant. Une formulation, permettant un bon compromis entre comportement rhéologique et réactivité de la suspension, définition et maintien mécanique des pièces macroporeuses mises en forme, a été retenue. Après optimisation des paramètres du procédé, l’étude de la surpolymérisation, en fonction des dimensions et des géométries des macropores, a conduit à un modèle prédictif de dimensionnement de ceux-ci, utilisé pour la conception assistée par ordinateur des pièces. Des échantillons modèles, contenant des macropores de différentes tailles (>300 μm) et de géométries variées, ont ensuite été confectionnés. L’influence de la température et de la durée du frittage, sur la microstructure des céramiques, a été précisée. Un taux de microporosité ouverte contrôlé sur une large gamme (jusqu’à 37 %) a pu être obtenu par ajustement de ces paramètres de frittage. L’amélioration de l’ostéointégration des substituts osseux passe par l’optimisation de leur architecture poreuse. Dans ce contexte, afin d’évaluer l’influence de la géométrie des macropores sur les phénomènes biologiques impliqués dans l’ostéogénèse, des études de prolifération de cellules osseuses in vitro et de vascularisation ex vivo ont été menées sur les substrats poreux de SiHA
Macro-micro-porous bioceramics made of silicated hydroxyapatite (SiHA), with a controlled architecture, were shaped by microstereolithography and consolidated by sintering. For this purpose, slurries with SiHA particles, dispersed in organic photosensitive medium, were developed. Their rheological behaviour was studied according to the powder, organic diluent and dispersant amounts. A formulation, allowing a good compromise between rheological behaviour and reactivity of the suspension, definition and mechanical strength of the shaped macroporous parts, was chosen. After optimization of the process parameters, the study of the overcure, according to the dimensions and the geometry of the macropores, has led to a predictive sizing model of pores, used for the computer aided design of the parts. Model specimens, containing different pore sizes (> 300 μm) of several geometries, were then shaped. The influence of the sintering temperature and time, on the ceramic microstructure, was investigated. A controlled amount of open microporosity over a wide range (up to 37%) was obtained by adjusting these sintering parameters. Improving the osteointegration of osseous substitutes requires an optimization of their architecture. In this context, in order to assess the effect of the geometry of the macropores on the biological phenomena involved in osteogenesis, in vitro studies of bone cells proliferation and ex vivo studies of vascularization were performed on the SiHA porous substrates

The ain of this work was to provide a deeper understanding of the electronic and geometrical structures of HA when substituted by various ions considered important in the field of biomaterials. Calculations were carried out using Density Functional Theory, (DFT), on bulk and surface, substituted-HA structures. Particular attention is given to the substation of phosphate ions by silicate ions. Bulk structures are investigated with supercells and the Virtual Crystal Approximation, which simulates low concentrations (up to 2.8 wt%) of silicon in the unit cell. The amount of silicon that can be substituted into a single cell is limited by the need for charge compensation, as the silicate ion has a formal charge of -4 and phosphate -3. Charge compensation is therefore explored, showing that hydroxyl-deficient HA is more favourable than stoichiometric HA when silicon is introduced. The HA-britholite-(Y) solid state series is also investigated, using geometry optimisation and theoretical NMR spectra, as a potential way of increasing the silicon content of a unit cell by charge compensating with the replacement of a +2 calcium ion by a +3 yttrium ion. Further substitutions of titanium and magnesium are also thoroughly investigated with the single unit cell model. A HA (100) surface slab is also constructed and electronically optimised. This model is used in the study of surface structures and interactions and is compared to previous experimental and theoretical results. Substitution of silicon into the surfaces is investigated in addition to protonation of surface phosphate and silicate ions and the adsorption of a glutamic acid fragment.

The direct synthesis of hydroxyapatite─1,8-octan-bisphosphonic acid (HAp─BISPH) nanocrystals has been carried out in presence of increasing amounts of BISPH in solution, by hydrothermal method at 120 °C for 15 h. XRD, IR, NMR-MAS (31P, 1H and 13C), TEM, AFM, TGA and chemical analysis were used to characterize the structure, morphology and composition of the products. X-ray powder diffraction patterns show that the incorporation of bisphosphonate moieties induces a significant loss of the material crystallin-ity and a clear decrease of the crystallite size. TEM and AFM images show that the precipitated apatite particles prepared in the presence of this bisphosphonic acid are nanosized. The IR and NMR-MAS 1H spectroscopy show that the BISPH can replace the OH− groups of the apatitic structure. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35199

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xiv, 190 p.; also includes graphics. Includes bibliographical references (p. 166-190).

Ceramic Hydroxyapatite (CHT), with empirical formula (Ca5(PO4)3OH)2, is a material used as ion exchange resin in chromatographic applications. The material, having both positive and negative charged sites, can be used in many different contexts encountered in the protein purification processes. Nevertheless, the resin shows an intrinsic limitation for this kind of applications: even if the material solubility in water is very low at pH values higher than 6.5, it sharply increases in more acidic environments, reducing the life of the material and increasing the operative costs of the process, making problematic the CHT application at these conditions. There is a further complication related to the CHT application: it is experimentally reported that the result of the resin interactions with salts is a pH transient occurring in the liquid phase of the chromatographic column. These pH variations are temporary but remarkable, they may influence in an important manner the material solubility, affecting the number of utilization cycle of the fixed bed and, eventually, the stability of the proteins involved in the separation process. In this work the principal aspects contributing at the selection of the operating pH and of the buffering specie are analyzed, discussing also the effect of the buffer itself on the material solubility. Then, it is reported a mathematical model useful for the description of the dynamic behavior of the column and it is proposed an interaction mechanism between the salts of the mobile phase and the stationary phase. In particular, it is emphasized the discussion regarding the different affinity shown by the stationary phase for the different counter-ions which may accompanies the buffering specie. Finally, a series of equations are developed at the scope to obtain a model useful to describe the observed pH transients.

Silicate substitution in hydroxyapatite (HA), with a substitution limit of ~5.2 wt%, has been shown previously to enhance the bioactivity of this material in vivo. The current study describes the substitution of greater levels of silicate via a coupled substitution of yttrium and silicate ions for calcium and phosphate ions, respectively. This was carried out using two different substitution mechanisms, and silicate levels of up to 11.25 wt% were incorporated; these compositions were characterised extensively. There was not a clear correlation between the surface properties of samples produced by the different mechanisms and the growth behaviour of MG-63 osteoblast-like cells, although there was a correlation with substitution mechanism. Following the success in increasing the level of silicate substitution in HA via the co-substitution of the Y³⁺ ion, the synthesis of similar materials, but substituting another ion in place of Y³⁺, was attempted. Gadolinium was chosen for its similar size, but primarily because of its use in MRI contrast agents. Similar levels of silicate substitution to the Y³⁺/SiO₄^4- co-substituted materials were achieved for both mechanisms. An MRI study showed improved contrast of the Gd³⁺/SiO₄^4- co-substituted compositions compared to stoichiometric HA, which suggests that these new compositions may have clinical applications where bone repair and implant resorption could be monitored using MRI. Carbonate-substituted HA is the subject of the final part of this study. The effect of the synthesis route upon the resulting carbonate location within the lattice is examined. Since CHA can be synthesised to contain sodium ions as a co-substituted ion, or as a sodium-free composition, investigations were carried out to find a synthesis method for both types of composition.

Since the early 1970's there have been a number of investigations into the preparation of dense sintered hydroxyapatite for medical applications. However, there have been few studies reporting the production of sintered carbonate apatite, which resembles more closely the composition of human bone mineral. This work has studied the precipitation, processing and sintering of carbonate apatites. Crystallisation variables such as temperature and bicarbonate ion concentration have been investigated in order to determine some effects on the size, morphology and composition of carbonate apatite precipitates. By employing the correct conditions, nanoscale precipitates have been produced that have enabled the use of a colloidal filtration route in processing. The effect of sintering atmosphere, green density, and carbonate content were investigated isochronally over a range of temperatures. Isothermal experiments demonstrated the evolution of microstructure and changes in density with time. Results from this study indicated that translucent 99.9% relative density carbonated hydroxyapatite could be produced by sintering in an atmosphere of carbon dioxide and water. Water was found to enhance densification in carbon dioxide furnace atmospheres. The temperature at which maximum densification occurred decreased with carbonate content. Bloating was found to be related to carbonate content as larger expansions were observed in higher carbonate content materials. The partial pressure of water did not effect the composition of the carbonate apatite, whereas the green composition did, contrary to the findings of other workers.

Ceramics used for medical purposes are known as bioceramics, such as hydroxyaptite (HA), which is one of the most well studied bioceramics because of its similar composition to human bone and also good biocompatibility, is bioactive and has excellent osteoconductivity. In addition many properties of HA can be improved by the addition of specific elements into its structure. The research in this thesis investigates the substitution of some selected elements into the structure of HA and subsequent characterisation in terms of physical, mechanical and biological responses. Si/S-HA and Sr/B/S-HA was obtained from Lucideon and Ho/HA was synthesised in house. Initially a cell response to a variety of element oxides was performed to identify elements to avoid or potentially use for substitution. Dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho) and praseodymium (Pr) at 100 ppm showed better results for alkaline phosphatase activity than 25 ppm in culture medium.2.5 and 5 mol.% of Ho was substituted into HA structure using a wet chemical method of synthesis. The samples were sintered at 1200°C for 10 hours. There was high crystallinity when 2.5 mol.% of Ho was added into the HA structure. Substitution of Ho in HA structure had the effect of shortening in a axis and elongation in c axis along with the higher concentration of Ho ion.2 mol.% of Si and S was also substituted into HA structure, where both elements Si and S replace PO4 site in HA structure. Si substituted in SiO4 form and S substituted in SO4 form for PO4 as confirmed by FT-IR results. Osteoblast-like cells cultured on Si/S-HA showed an increase in alkaline phosphatase, collagen type I and ostecalcin on samples sintered at high temperature. Sr/B/S-HA was also made where 2 mol.% of each element was substituted into the HA structure. The best condition of sintering temperature for Sr/B/S-HA was 1100°C for 10 hrs due to the resulting small grain size, improved cell adhesion and more collagen and osteocalcin production. These results suggest that the substitution of elements into the HA structure can provide novel bioceramics for control of physical mechanical and cell responses properties.

Doutoramento em Ciência e Engenharia de Materiais
Graças aos desenvolvimentos na área da síntese de nanomaterais e às potentes técnicas de caracterização à nanoescala conseguimos hoje visualizar uma nanopartícula (NP) como um dispositivo de elevado potencial terapêutico. A melhoria da sua efectividade terapêutica requer no entanto o aprofundamento e sistematização de conhecimentos, ainda muito incipientes, sobre toxicidade, selectividade, efeitos colaterais e sua dependência das próprias características físico-químicas da NP em análise. O presente trabalho, elegendo como alvo de estudo uma substância considerada biocompatível e não tóxica, a hidroxiapatite (Hap), pretende dar um contributo para esta área do conhecimento. Definiram-se como metas orientadoras deste trabalho (i) estudar a síntese de nanoparticulas de Hap (Hap NP), e a modificação das características físico-químicas e morfológicas das mesmas através da manipulação das condições de síntese; (ii) estudar a funcionalização das Hap NP com nanoestruturas de ouro e com ácido fólico, para lhes conferir capacidades acrescidas de imagiologia e terapêuticas, particularmente interessantes em aplicações como o tratamento do cancro (iii) estudar a resposta celular a materiais nanométricos, com propriedades físico-químicas diversificadas. No que se refere à síntese de Hap NP, comparam-se dois métodos de síntese química distintos, a precipitação química a temperatura fisiológica (WCS) e a síntese hidrotérmica (HS), em meios aditivados com ião citrato. A síntese WCS originou partículas de tamanho nanométrico, com uma morfologia de agulha, pouco cristalinas e elevada área superficial especifica. A síntese HS à temperatura de 180ºC permitiu obter partículas de dimensões também nanométricas mas com área específica inferior, com morfologia de bastonete prismático com secção recta hexagonal e elevada cristalinidade. Com o objectivo de aprofundar o papel de algumas variáveis experimentais na definição das características finais das partículas de hidroxiapatite, designadamente o papel do ião citrato (Cit), variou-se a razão molar [Cit/Ca] da solução reagente e o tempo de síntese. Demonstrou-se que o ião citrato e outras espécies químicas resultantes da sua decomposição nas condições térmicas (180ºC) de síntese tem um papel preponderante na velocidade de nucleação e de crescimento dessas mesmas partículas e por conseguinte nas características físico-químicas das mesmas. Elevadas razões [Cit/Ca] originam partículas de dimensão micrométrica cuja morfologia é discutida no contexto do crescimento com agregação. Com o objectivo de avaliar a citotoxicidade in vitro das nanopartículas sintetizadas procedeu-se à esterilização das mesmas. O método de esterilização escolhido foi a autoclavagem a 121º C. Avaliou-se o impacto do processo de esterilização nas características das partículas, verificando-se contrariamente às partículas WCS, que as partículas HS não sofrem alterações significativas de morfologia, o que se coaduna com as condições de síntese das mesmas, que são mais severas do que as de esterilização. As partículas WCS sofrem processos de dissolução e recristalização que se reflectem em alterações significativas de morfologia. Este estudo demonstrou que a etapa de esterilização de nanopartículas para aplicações biomédicas, por autoclavagem, pode alterar substancialmente as propriedades das mesmas, sendo pois criticamente importante caracterizar os materiais após esterilização. Os estudos citotoxicológicos para dois tipos de partículas esterilizadas (HSster e WCSster) revelaram que ambas apresentam baixa toxicidade e possuem potencial para a modelação do comportamento de células osteoblásticas. Tendo em vista a funcionalização da superfície das Hap NP para multifunções de diagnóstico e terapia exploraram-se condições experimentais que viabilizassem o acoplamento de nanopartículas de ouro à superfície das nanopartículas de Hidroxiapatite (Hap-AuNP). Tirando partido da presença de grupos carboxílicos adsorvidos na superfície das nanopartículas de Hap foi possível precipitar partículas nanométricas de ouro (1,5 a 2,5 nm) na superfície das mesmas adaptando o método descrito por Turkevich. No presente trabalho as nanopartículas de Hap funcionaram assim como um template redutor do ouro iónico de solução, propiciando localmente, na superfície das próprias nanopartículas de Hap, a sua redução a ouro metálico. A nucleação do ouro é assim contextualizada pelo papel redutor das espécies químicas adsorvidas, designadamente os grupos carboxílicos derivados de grupos citratos que presidiram à síntese das próprias nanopartículas de Hap. Estudou-se também a funcionalização das Hap NP com ácido fólico (FA), uma molécula biologicamente interessante por ser de fácil reconhecimento pelos receptores existentes em células cancerígenas. Os resultados confirmaram a ligação do ácido fólico à superfície das diferentes partículas produzidas HS e Hap-AuNPs. Graças às propriedades ópticas do ouro nanométrico (efeito plasmão) avaliadas por espectroscopia vis-UV e às potencialidades de hipertermia local por conversão fototérmica, as nanoestruturas Hap-AuNPs produzidas apresentam-se com elevado interesse enquanto nanodispositivos capazes de integrar funções de quimio e terapia térmica do cancro e imagiologia. O estudo da resposta celular aos diversos materiais sintetizados no presente trabalho foi alvo de análise na tentativa de se caracterizar a toxicidade dos mesmos bem como avaliar o seu desempenho em aplicações terapêuticas. Demonstrou-se que as Hap NP não afectam a proliferação das células para concentrações até 500 g/ml, observando-se um aumento na expressão genética da BMP-2 e da fosfatase alcalina. Verificou-se também que as Hap NP são susceptíveis de internalização por células osteoblásticas MG63, apresentando uma velocidade de dissolução intracelular relativamente reduzida. A resposta celular às Hap-AuNP confirmou a não citotoxicidade destas partículas e revelou que a presença do ouro na superfície das Hap NP aumenta a taxa proliferação celular, bem como a expressão de parâmetros osteogénicos. No seu conjunto os resultados sugerem que os vários tipos de partículas sintetizadas no presente estudo apresentam também comportamentos interessantes para aplicações em engenharia de tecido ósseo.
Thanks to the last developments in the field of nanomaterials synthesis and to the powerful characterization techniques at the nanoscale, a nanoparticle (NP) can now be viewed as a device of high therapeutic potential. The improvement of its therapeutic effectiveness however still requires the deepening and systematization of important knowledge, still very incipient, on critical related issues including toxicity, selectivity, side effects and their own dependence on the physicochemical characteristics of the NP under analysis. The awareness of this need has framed the present work whose material target is a substance currently considered as biocompatible and nontoxic, hydroxyapatite (Hap), aiming to contribute to the referred pool of knowledge. The guiding goals of this work are here stated as: (i) to study the synthesis of nanoparticles Hap (Hap NP) for understanding the control of particle physico-chemical characteristics through the manipulation of its synthesis conditions, (ii) to study the functionalization of Hap NP with gold and with folic acid in order to impart both imaging and therapy abilities to the synthesized NP thus addressing their usefulness for particular applications related to the treatment of cancer, (iii) to examine the cellular response to nanosized materials having diverse physicochemical properties. For the study of Hap synthesis a hydrothermal synthesis (HS) technique assisted by citric acid additive was followed. The potential of citrate ion (Cit) for tailoring the synthesized particle morphology was exploited by varying the molar ratio [Cit:Ca] of the starting precursor solution. It was demonstrated that the citrate ion and/or other chemical species resulting from citrate decomposition at the used synthesis temperature (180°C) has a major role on nucleation and growth processes of the resulting Hap particles and on their final physico-chemical characteristics. Prismatic Hap particles with hexagonal cross section but with nanometric dimensions were obtained for a low [Cit:Ca] ratio while increasing ratios originated micrometer-sized particles composed by assembled fiber-like or sheet-like particles whose morphology may be discussed in the framework of an aggregation assisted growth. The evaluation of the biological performance of the produced nanometric Hap particles was the natural step in the present study. However, for the goal of comparing the impact of Hap NP morphology variations on cell response, a second chemical precipitation method (WCS) at physiological temperature and using the same additive was also adopted to produce thinner Hap NP. The physico-chemical characteristics of the two precipitated particles, i.e. HS and WCS Hap NP, were comparatively discussed, being found that thin needle-like particles of very high specific surface area (170 m2/g) are obtained from WCS as compared to the prismatic HS particles of lower specific surface area (55 m2/g) but of higher crystallinity. Moreover, as in vitro studies require sterilized materials, the particles were autoclaved at 121º C and the sterilization impact on the particles properties was evaluated as well. Contrarily to WCS particles no significant changes are observed on HS morphology, consistently with the high synthesis temperature conditions for HS NP that exceed largely autoclaving condition. WCS particles undergo dissolution and recrystallization processes which are reflected on significant changes of WCS NP morphology. These results demonstrate that autoclaving sterilization may substantially alter the properties of NP intended for biomedical applications being thus critically important to characterize the materials after sterilization. The in vitro cytotoxicity studies on both type of sterilised particles (HSster and WCSster) revealed that they present low toxicity and have potential for the modulation of the osteoblastic cell behaviour. The possibility of functionalizing Hap NP surface for multifunction purposes (diagnosis and therapy, for instance) was also exploited in the present work. Taking advantage from the presence of adsorbed carboxylic groups left by the synthesis process, HS NP surfaces could be used as a kind of template for gold precipitation, thus providing a new approach to Turkevich method for gold precipitation. Gold nanoparticles with an average diameter of 1.5 to 2.5 nm were effectively precipitated on HS nanoparticles facets as revealed by transmission electron microscopy (TEM). The reducing ability of the species adsorbed on HS surface including carboxylate compounds derived from citrate was thus confirmed as gold ions supplied by the neighbouring gold solution underwent a local reduction giving place to metallic gold spots and hence to nanostructured hydroxyapatite-gold nanoparticles (Hap-AuNPs). The functionalization of Hap NP with folic acid (FA), a molecule with high biological interest due to its easy recognition by the receptors on tumor cells, was also studied. The results confirmed the conjugation of FA to the surface of HS and Hap-AuNPs nanoparticles. Thanks to the optical properties of Hap-AuNPs imparted by the nanometric gold (plasmon effect) as confirmed by UV-vis spectroscopy and to the hyperthermia effect reported for metallic nanometric gold, the Hap-AuNPs here produced show a great potential as nanodevices able to integrate functions of chemical and thermal therapy for cancer and imaging. The cellular response to the various nanomaterials synthesized in this work was also analysed in an attempt to characterize their toxicity and to assess their biological performance aiming to identify potential therapeutic applications. It was demonstrated that Hap NP do not affect MG63 cell proliferation until concentrations up to 500 g/ml, as indicated by BMP-2 and alkaline phosphatase expression. It was also found that Hap NP undergo internalization by MG63 osteoblast cells, suffering a relatively low intracellular dissolution rate. The cellular response to Hap AuNPs confirmed their non-cytotoxicity while showing that the presence of gold at the surface of Hap NP increases the cell proliferation rate and the expression of osteogenic parameters. Altogether the in vitro results suggest that the behavior of the various types of particles synthesized in this study addresses a potential interest for applications in hard tissue engineering.

In this dissertation, hydroxyapatite-based and hydroxyapatite with carbon composite materials have been rationally designed, synthesized, characterized and applied to processes of environmental concern, namely wastewater remediation (as sorbents) and electrochemical CO2 reduction reaction, CO2RR (as electrocatalysts). Pristine hydroxyapatite (HAP, Ca10(PO4)6(OH)2) and composite HAP/carbon materials have been synthesized according to a simple wet co-precipitation route. Composition, structure and morphology of samples have been investigated by a plethora of physical-chemical techniques (i.e. ICP/OES elemental analyses, N2 adsorption/desorption isotherms, XRD, TEM (and STEM) imaging, TEM/EDX mapping, transmittance FT-IR and Raman spectroscopies, and XPS). Since adsorption onto materials’ surface is crucial in both sorption and catalytic applications, a special attention has been devoted to surface properties, determined by means of zeta potential measurements, gas-solid calorimetric/volumetric titrations, and liquid-solid volumetric titrations, thus assessing the amphoteric nature of HAP-based surfaces. At first, pristine pristine HAP has been studied as sorbent for the remediation of inorganic pollution in wastewater (i.e. heavy metal cations such as Cu(II), Pb(II), Cr(III), Ni(II) and Co(II)). Stirred batch adsorption tests and collection of adsorption isotherms in solutions containing both individual and mixtures of heavy metal cations allowed to quantitatively assess HAP sorption ability. Ad-hoc experiments (i.e. microcalorimetric adsorption isotherms) and physical-chemical investigation of metal-loaded samples shed light on the adsorption mechanisms of several polluting species onto HAP surface. Eco-friendly HAP/carbon composites from renewable resources have been instead applied to the remediation of more complex effluents, where simultaneous organic and inorganic pollution may occur. Thanks to their dual nature, HAP/carbon composites exerted outstanding adsorption performances towards both class of polluting species. Both in the form of pristine HAP and HAP/carbon composites, the sorbents exhibited a strict retention of adsorbed pollutants when undergoing leach testing, therefore ensuring no secondary pollution issues. In an exploratory study, HAP/carbon composites have been also implemented as modifiers in self-standing and mechanically stable electrodes for the electrochemical detection of heavy metal cations traces in waterbodies. Benefitting from the pronounced HAP affinity towards such species, encouraging results have been obtained on the detection of some benchmark pollutants, although the registered limits of detection (ca. one order of magnitude improvement to match legislative requirements) and linearity ranges currently limit HAP/carbon modified electrodes applications. Finally, during a 6-months stay at University of California Irvine (UCI), hosted by Prof. Plamen Atanassov group, HAP has been applied as dopant in CO2RR electrocatalysts. The peculiar ability of HAP amphoteric surface to adsorb and destabilize CO2 (i.e. breakage of its linearity) has been exploited in composite electrocatalysts, composed by copper nanoparticles (active phase) and HAP (dopant), supported on N-doped 3D assembly of graphene nanosheets (3D-GNS, carbonaceous support). When tested in a lab scale CO2 electrolyzer, HAP-doped electrocatalysts displayed a faradic efficiency (FE) towards CO2RR ≥ 80% throughout the whole potential range under investigation, minimizing parasitic Hydrogen Evolution Reaction (HER). Interestingly, HAP doping actually altered CO2RR product distribution: in particular, small quantities of C2+ products were produced under low applied overpotential while at higher voltage formate production was boosted. Product distribution alteration has been rationalized taking into account the ability of HAP acid-basic surface groups to stabilize CO2 reduction intermediate species, directing the the selectivity of electrochemical CO2RR processes. Overall, the present study demonstrates that the unique features of HAP make it a versatile material which may be applied for the protection of the environment at 360 degrees, from water to air remediation, as pristine and/or composite material, as sorbent and/or catalysts’ dopant.

Silicon doped hydroxyapatite (SiHA) could be used as a thin film coating on load bearing bone implants to provide a bioactive layer enabling bone to form a direct bond with the implant/bone interface thus increasing implant lifetime by lowering the chances of aseptic loosening. This study has been undertaken to investigate silicon additions to RF magnetron sputtered hydroxyapatite (HA) thin films. Detailed characterisation was carried out on SiHA thin films to establish the structural, chemical, mechanical and compositional properties. Silicon content was altered by adjusting the power density applied to silicon targets in a co-deposition process resulting in SiHA films containing 0.0, 1.8, 4.2 and 13.4 wt.% silicon. All as-deposited thin films were found to be amorphous. After annealing at 600˚C in flowing argon for 2 h, it was found that films exhibited a single phase HA structure. The addition of silicon inhibited HA crystallite growth and acted to lower the stability of HA films in aqueous solutions. The 13.4 wt.% SiHA thin film did not recrystallise until a heat treatment at 800˚C. From the work presented here, it is proposed that, in post-plasma-deposited heat treated films, silicon substitutes as silicate species into the HA lattice. Asdeposited silicon containing thin films were found to be amorphous and have a polymeric silicate configuration, suggesting that, silicate groups may be randomly distributed throughout the amorphous film. After post-deposition annealing silicon containing films were in a monomeric state suggesting silicate groups had substituted for phosphate tetrahedra in the HA lattice. Furthermore, an HA-like phase was found to be present. Contrary to these findings, FTIR analysis did not manifest any silicate-based bands. This may, however, be due to the fact that technique used only samples a very small amount of material and, due to the low doping quantities of silicon in the HA films. Furthermore, Ca/P ratios consistently differed from the stoichiometric value of HA (1.67). This combined evidence raises the question of whether the post-deposition heat-treated films have a true HA-like structure. More work is required in order to truly understand the structures present in heat-treated SiHA thin films. HA thin film composition is commonly measured in terms of the Ca/P ratio. Energy dispersive X-ray analysis (EDX) and XPS were evaluated in terms of accuracy in conjunction with Rutherford backscattering spectroscopy (RBS) to measure the Ca/P ratio of HA thin films to establish the most appropriate technique for accurate compositional analysis. This was was found to the RBS, achieving an accuracy of within 2 %, with EDX averaging 8 % and XPS ranging from 25 - 42%. It was concluded that XPS gave such large differences in values because the top few atomic layers of thin films was of a different composition than the bulk of the coating. A Human osteoblast cell (HOB) model was used to establish the in vitro cellular response of SiHA thin films. Initially, HA and SiHA thin films annealed at 600˚C were compared. Cells attached and proliferated well on HA surfaces compared to SiHA surfaces, however, improved cell growth was seen with increasing silicon content. Dissolution studies showed that SiHA thin films were highly unstable in cell culture media and it is thought that the films dissolved, and where cell adhesion and growth did occur it was because cells adhered to the titanium substrates beneath the films. This was then compared with HA and SiHA thin films annealed at 700˚C. No significant difference was found between the two surfaces in terms of cell growth or protein expression indicating that silicon content and crystallinity play an important role in the cellular response of SiHA thin film.

Pulsed laser deposition (PLD) was used to deposit hydroxyapatite (HA) thin films on various substrates, including silicon (100) and titanium (Ti-6Al-4V) alloy. Thin films of amorphous HA were deposited at room temperature and then annealed over a range of temperatures. The microstructure and composition of the films were determined using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD). The HA films were found to achieve total crystallinity at 350㮠The mechanical properties of the films were studied by means of nanoindentation and scratch adhesion testing. Crystalline and adherent HA thin films prepared using PLD and post deposition annealing have many potential medical and dental applications.

Biodegradable scaffolds are an important aspect of bone tissue engineering as they provide an alternative approach to bone grafts and biomaterials substitutes. The work achieved in this thesis describes the manufacturing process of collagen and collagen-hydroxyapatite scaffolds. Bovine type I collagen has been mixed to commercially obtained and manufactured hydroxyapatite (HA) particles to mimic the main natural extracellular components ofbone. Collagen sheets possessing different levels of dehydration - air drying (AD), dehydrothermal treatment (DHT) and CPD - have been characterised using infrared (FTIR), thermal (DSC), topographical (AFM), mechanical (DMA) and biodegradation (collagenase assay) analyses. Severe dehydration by CPD does not appear to denature nor crosslink collagen, but results in the reduction of the fibrils d-banding periodicity from 67nm to 63.7nm. Collagen exposed to DHT showed increased Young's modulus (E) and resistance to biodegradation, suggesting the formation of intermolecular crosslinks. However, thermal and infrared analyses indicated denaturation of the tropocollagen molecule, especially at high temperature oftreatment (l20°C). HA particles have been manufactured using a wet chemical synthesis to resemble bone apatite. The calcium phosphate phase of HA was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). These particles contained 6.2% carbonate substitution (type A and type B) and were constituted from smaller rod-like crystals of the order of 15-20nm in diameter and 79-120nm in length. The ability to manufacture collagen-HA scaffolds is shown to rely on the stability ofthe swollen collagen fibres in the initial dispersion, which is pH dependent. Changing the collagen and HA content of the dispersion as well as the freezing rate during processing had an effect on the porosity, pore size distribution, mechanical properties and biodegradation rate ofthe composite scaffolds. Hybrid scaffolds have been manufactured containing different regions displaying varying properties. Finally, a solid freeform fabrication process has been developed to produce 3D moulds of stearic acid. This process allows for the external shape of the scaffold to be tailored and for internal architectures, such as microchannel pathways, to be incorporated within. These are essential developments in the field oftissue engineering.

Hydroxyapatite (HA) is a highly biocompatible calcium phosphate which closely resembles the mineral component of bone. Porous structures composed of biocompatible materials are believed to enhance fixation (and integration) as they encourage the ingrowth of bone into the implant. Consequently there is great interest in the potential of porous HA as an alternative to bone homo grafts and auto grafts. However, despite the interest in the field, there has been no thorough investigation into the physical and structural properties of porous HA and their effects on bone ingrowth. The material used in this study was a carbonated apatite (containing < 0.9 % levels of trace element impurities) with a trabecular macrostructure, that had been converted from bovine cancellous bone. The apparent density of the material ranged from 0.35 -1.45 g.cm-3 and the macrostructural morphology varied from an open equiaxed foam to a columnar honeycomb-like structure. The ultimate compressive stress was strongly related (r = 0.9) to the square of the apparent density, while compressive modulus was influenced by both apparent density and macrostructural morphology. Transmission electron microscopy of human osteoblast-like cells cultured on the material demonstrated that cells were closely associated with the surface. Specimens with densities of 0.6.0.9 and 1.2 g.cm-3 were then implanted in a lapine cancellous site for periods of 10 days, 3, 5, 13 and 26 weeks. After implantation all specimens elicited a highly biocompatible response, with active areas of bone deposition, remodelling and revascularization and no fibrous encapsulation. The amount of bone ingrowth within the implant (25-10%) after.5 weeks was found to vary with apparent density (0.6-1.2 g.cm-3) indicating that osseointegration was a function of macrostructural morphology. Pushout testing of retrieved spedmens indicated that all implants were securely fixed by 5 weeks (2-3 MPa). Compression testing demonstrated that after 5 weeks low density implants were sufficiently reinforced by bone ingrowth to equal the compressive strength of the host tissue (6 MPa) which increased to approximately 20 MPa at 3 and 6 months.

This thesis is focused on the development of synthesis and characterisation protocols for two different nanoparticulate materials; hydroxyapatite (HA), a biomaterial well recognised as chemically akin to human bone, and CaO, a material often used for the sequestration of CO2 at elevated temperatures. For the analysis of these materials various bulk and particle level characterisation techniques have been employed, which are complemented by the versatile analytical methods available in the transmission electron microscope (TEM). The first chapter of results reveal that a hydrothermal synthesis route achieved phase-pure nanoparticulate HA with Ca/P atomic ratios close to the stoichiometric target (1.67). Impure HA nanopowders were produced by a sol-gel synthesis route with analysis by X-ray diffraction (XRD) revealing secondary phases of calcium phosphates, CaCO3 and CaO. The Ca/P ratios of each powder were determined at the particle level using TEM with energy dispersive X-ray spectroscopy (TEM-EDX), having first established a threshold electron fluence below which significant electron-beam-induced alteration of the composition of HA does not occur. Results showed a greater variability of particle composition from the sol-gel preparation route compared to the hydrothermal route. This technique provides results in reasonable agreement to bulk Ca/P ratio analysis carried out by X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The second component of the thesis relates to the production of nanoparticulate CaO powder sorbents for the sequestration of CO2 gas. The CaO nanopowders were produced by the thermal decomposition of calcium acetate hydrate (CaAc); this process was analysed by thermogravimetric analysis (TGA) and by in-situ hot-stage XRD. The CO2 uptake capability of the CaO powder sorbents was analysed by TGA following the reaction: CaO + CO2 ↔ CaCO3 Results showed a molar conversion ratio, χ (of CaO to CaCO3) of 0.92, after 15 minutes of carbonation with structural analysis by SEM and TEM showing consistent growth and densification of rounded CaCO3 crystals upon carbonation. Multiple cycles of carbonation and decarbonation were then carried out by TGA to investigate sorbent regenerability. A 0.32 decrease in χ was found after 9 cycles which is attributed to the sintering (reduction in surface area) of the sorbent with progressive decarbonations at 800 °C. Structural analysis of decarbonated samples extracted from the TGA, by XRD, SEM and TEM, highlighted the issue of sorbent hydration upon storage, sample preparation and analysis. A TEM based technique has been developed for the structural analysis of multicycle CO2 capture using an ex-situ environmental cell (E-cell). This technique allows for multicycle capture to be carried out and then analysed in the TEM with minimal exposure to the atmosphere, therefore providing a closer microstructural match to what occurs in the TGA. Results showed that slow, low-vacuum decarbonation (in the E-cell) creates a densified ‘skeleton’ of CaO, consistent with the drop in capture capacity observed by TGA. Finally, modifications of CaO sorbents using spacer materials has been carried out with the aim of declining the decay in sorbent performance during multiple cycles of carbonation and decarbonation in the TGA. Promising results were found using CaO sorbents modified a commercial YSZ powder and also with CaZrO3/ZrO2.

Quantifying the surface composition of hydroxyapatite, the structural prototype of the main inorganic constituent of bone, teeth and other calcified tissues in nature, is the first step in understanding the surface-solution equilibria of the biological solutions in contact with calcified tissue. The surface concentrations of calcium and phosphorus on hydroxyapatite in aqueous media in the pH range 5.62 to 8.19 were determined using a radioisotope exchange technique. The effect of 0.1 M KCl, 0.1 M NaCl and water on the surface composition was also determined. Trace amounts of radioactive calcium (45ca) and phosphorus (32PJ were added to aqueous hydroxyapatite suspensions at thermodynamic equilibrium following sequential washing to achieve a constant surface at any given pH. At isotopic equilibrium, the radioactive calcium and phosphorus in solution were determined by liquid scintillation counting and, with the use of appropriate isotope exchange equations, it was possible to calculate the surface concentration of calcium and phosphorus using the surface area of the solid. The surface composition varied with pH, the variation being due to the change in surface phosphorus, since the surface calcium changed little over the pH range tested. The increase in surface phosphorus concentration with decreasing pH was attributed to the effect of the surface charge on the adsorption of phosphorus from solution. The surface phosphorus concentration could be predicted from the solution pH, but the same was not true for surface calcium which was shown to be independent of pH. Using the radioisotope exchange technique~ there was no difference in the measured surface composition in 0.1 M KCl~ 0.1 M NaCl and water indicating that 0.1 M KCl and 0.1 M NaCl behave as indifferent electrolytes towards the surface of hydroxyapatite. On the basis of the measured surface composition over the pH range tested~ the surface of hydroxyapatite in aqueous solution was considered to be consistent with (1) the model of Brown (1966) which assumes that the solid is covered with a half unit cell layer of octacalcium phosphate and (2) the surface charge-dependent adsorption of ions proposed by Bell and Mika (1979).

The thesis deals with the precipitation synthesis of nanoparticle hydroxyapatite with goal to study the influence of reaction conditions on the morphology of the particles. The theoretical part is focused on biomaterials, bioceramics and phosphates characterization. Further the work is focused on hydroxyapatite, its characteristics and possible synthesis in particular. The synthesis of hydroxyapatite precipitation is described in the experimental part. Syntheses were performed at a reaction temperature of 0-80 °C at pH = 8-11, at the aging time of 0-24 h, in the presence of surfactant and the chelating agent and with the post-precipitation hydrothermal or ultrasonic treatment. For characterization of the prepared powders, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), laser diffraction (LD) and the analysis of the specific surface area (BET) were used. Pure hydroxyapatite powders or a mixture of hydroxyapatite and tricalcium phosphate were prepared by precipitation syntheses. HA particle morphology was strongly affected by the reaction temperature – with increasing temperature the larger particles with a clearer morphology were formed, mostly in the rod shape. Postprecipitation hydrothermal treatment had a significant influence on the morphology of HA particles – it caused the formation of spherical or slightly elongated particles. The reaction medium of water/ethanol significantly affected the particle morphology – it inhibited the particle growth.

Biodegradable metallic materials for medical applications have received considerable attention in recent years. The main reason is that they provide high potential for fabrication of temporal orthopedic implants such as bone fixation devices. Magnesium is an excellent candidate for fabrication of biodegradable implants due to its biocompatibility, mechanical properties similar to human bone and relevance for biological body functions. The fast degradation rate of magnesium and its biodegradable alloys in physiological environment limits its clinical application. Another attractive material in the field of biodegradable materials is zinc, which is among the essential elements in human body. Zinc exhibits an excellent corrosion resistance, and inferior biocompatibility compared to with magnesium. Hence, surface modification to form a hard, dense/porous, biocompatible and corrosion resistant modified layer has become an interesting topic in magnesium base biomaterials. Since hydroxyapatite is well tolerated by living organisms and in addition, improves the bone growth, it appears to be excellent candidate for such coatings on surface of biodegradable materials (e.g. Mg, Zn). This thesis is focused on comparison of corrosion behavior of pure non ferrous metals (Mg, Zn) and metals coated with hydroxyapatite, in simulated body fluids. The present approach is the use of modified atmospheric plasma spray technology to produce the hydroxyapatite coatings – suspension spraying. Composition and structure of the coatings and corrosion products were studied by light microscopy, scanning electron microscopy equipped with energy dispersive microanalyzer and X-ray diffraction. Corrosion of Mg and Zn samples was monitored by weight loss and determined by X ray and micro-tomography. The application of the HA coating resulted in decrease of corrosion rate of pure Mg. The corrosion rate of coated Mg samples was lower by 27,3 % in comparison with the corrosion rate of pure non coated Mg. Corrosion degradation of uncoated and coated Zn samples was minimal. The aplication of HA on the non ferrous surface appears to be a very promising method to improve corrosion and biological properties of these biodegradable materials.

The diploma thesis is related to the preparation of hydroxyapatite complex structures by additive manufacturing known as Lithography based ceramics manufacturing – LCM. A photosensitive suspension containing hydroxyapatite particles was used for 3D printing of ceramic complex structures. The influence of printing parameters on the resulting macrostructure, microstructure, density, and dimensional accuracy was evaluated. The aim was to obtain ceramic components without delamination of the layers and optimise following post-processing steps (cleaning and thermal treatment). It was found that the exposure time has a significant effect on the dimensional accuracy of printed parts. During observation microstructure of printed parts, a microporosity at the interface of printed layers, which can cause delamination of several layers was identified. High-temperature dilatometry showed different temperature of beginning densification process in the longitudinal and perpendicular directions to the layers. That could be an initiation mechanism for delamination of the layers. X-ray diffraction analysis determined a single-phase composition of powder in photosensitive suspension and sintered parts. A commercial product LithaSol 20 was suggested as a suitable cleaning agent and efficiency of the ultrasound field for cleaning was demonstrated. Based on the thermogravimetric analysis an optimized cycle of heat treatment was designed. The optimisation led to time saving (49 hours), while maintaining density, dimensional accuracy and macrostructure of the 3D printed structures.

A processing route for development of hydroxyapatite (Ca10(PO4)6(OH)2 or HAp)-titania (TiO2) hybrid coatings on titanium alloy (Ti6Al4V) has been established. HAp powders of different size and morphology were synthesized by aqueous precipitation techniques using different precursor couples and XRD, SEM and FTIR were performed for complete characterization. Hybrid coatings were then prepared via sol-gel by incorporating presynthesized HAp powders into a titanium-alkoxide dip coating solution. Titania network is formed by hydrolysis and condensation of Ti-isopropoxide (Ti[OCH(CH3)2]4) based sols. The effect of titania sol formulation, specifically the effect of organic solvents on the microstructure of the dip coated films calcined at 500 º
C has been investigated. The coatings exhibit higher tendency for cracking when a high vapor pressure solvent, such as ethanol (C2H5OH) is used causing development of higher macroscopic stresses during evaporation of the sol. Titania sol formulations replacing the solvent with n-propanol (CH3(CH2)2OH) and acetly-acetone (C5H8O) combinations enhanced the microstructural integrity of the coating during evaporation and calcination treatments. Sol-gel processing parameters such as multilayer coating application and withdrawal rate can be employed to change the titania thickness in the range of 0.120 - 1.1 microns and to control the microstructure of HAp-titania hybrid coatings. Slower withdraw rates and multi-layer dip coating lead to coatings more vulnerable to cracking. A high calcination temperature in the range of 400 º
C-600 º
C lead to more cracking due to combined effect of densification originated stresses and thermal stresses upon cooling.

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.

Synthesis of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) from commercial grade plaster of paris (CaSO4&bull
0.5H2O, PoP) and gypsum (CaSO4&bull
2H2O) has been performed. HAp synthesis was achieved by reacting 1 M of (NH4)2HPO4 (or 0.5 M of (NH4)2HPO4) solutions with solid calcium sulfate precursors under ambient pressure (1 atm) and hydrothermal-like (2 ±
0.2 atm, 120 °
C) conditions. Under ambient conditions, HAp formation kinetics was investigated at 25 °
C, 50 °
C and 90 °
C using 1 M of (NH4)2HPO4 solution. Conversion to HAp at such low temperature takes more than 21 days and it also promotes formation of additional calcium phosphate with HAp. At 25 °
C, HAp formation started after 7 days accompanied with formation of brushite (CaHPO4&bull
2H2O). At 50 °
C no significant conversion was observed after 6 h. However, at 90 °
C, phase pure HAp was formed after 2 h. On the other hand, under hydrothermal-like conditions, the HAp formation proceed much faster and it was also shown that HAp could be also synthesized from gypsum powders and bulk gypsum pellets. Using 1 M of (NH4)2HPO4 solution, HAp formation from PoP started 15 min and completed almost in 30 min, whereas 0.5 M of (NH4)2HPO4 reactant solution slowed down the conversion. The exact chemical identity of the HAp product of hydrothermal-like reaction was evaluated by post-synthesis calcinations and the thermal phase stability was related with the stoichiometry (Ca/P at ratio) of the HAp. The HAp phase was stable up to 600 °
C and above 600 °
C, &beta
-tricalcium phosphate (&beta
-Ca3(PO4)2, &beta
-TCP) was formed, suggesting that the resultant HAp was calcium-deficient. Mechanical testing by diametrical compression was performed to the HAp samples produced from bulk gypsum pellets. The strength was measured 1.2 MPa with highest solid to liquid (s:l) ratio 3.33 and decreased with s:l ratio. This change was found to be related with the porosity differences due to differences in s:l ratio. Additional mechanical tests were applied to the polycaprolactone (PCL) coated bulk HAp pellets for which the tensile strength was doubled. This study presents an easy and feasible method for production of HAp from a cheap and abundant calcium source &ndash
PoP. In addition, the findings provide a potential processing route for developing irregularly shaped bulk porous HAp structures.

The clinical success of a bone-anchored implant is controlled by many factors such as implant shape, chemical composition, mechanical and surface properties. The surface properties (e.g. charge, wettability and roughness) are considered to be important parameters for the biological acceptance of the biomaterial, whereas the bulk properties control the biomechanical behaviour. For implants designed to be used in load-bearing applications in the skeletal system, the biomaterial should preferably integrate into bone tissue for a long lasting function. Lack of integration between the implant and bone increases the risk of micromotions, infections, soft tissue encapsulation, which all reduces the survival rate of the implant and makes revision surgery necessary. Coatings and surface modifications can be used to tailor properties of implant surfaces, and further improve the potential bone bonding and bone in-growth, compared to unmodified surfaces. A biomimetic method, developed by Kokubo, can be used to prepare a hydroxyapatite coating on to titanium substrates. The method is based on a solution based process where the compositions of the soaking medium and thus the formed coatings can be controlled. In this thesis, titanium (oxide) surfaces have been tailored via deposition of ion substituted hydroxyapatite coatings. Biologically relevant ions like strontium, silicon and fluoride were incorporated into apatite coatings. The substrates included well-defined rutile single crystals, as well as poly-crystalline titanium oxide surfaces and experimental Ti implants. The results showed that incorporation of substitute ions alters the morphology, crystallinity, composition and dissolution rates of apatite coatings. The in vivo effects of the ion substituted apatite coatings were also studied. The results showed that the ion substituted apatite coatings have good biocompatibility and can promote early bone formation.

Hydroxyapatite (HA) has received wide attention in orthopedics, due to its biocompatibility and osseointegration ability. Despite these advantages, the brittle nature and low fracture toughness of HA often results in rapid wear and premature fracture of implant. Hence, there is a need to improve the fracture toughness and wear resistance of HA without compromising its biocompatibility. The aim of the current research is to explore the potential of nanotubes as reinforcement to HA for orthopedic implants. HA- 4 wt.% carbon nanotube (CNT) composites and coatings are synthesized by spark plasma sintering and plasma spraying respectively, and investigated for their mechanical, tribological and biological behavior. CNT reinforcement improves the fracture toughness (>90%) and wear resistance (>66%) of HA for coating and free standing composites. CNTs have demonstrated a positive influence on the proliferation, differentiation and matrix mineralization activities of osteoblasts, during in-vitro biocompatibility studies. In-vivo exposure of HA-CNT coated titanium implant in animal model (rat) shows excellent histocompatibility and neobone integration on the implant surface. The improved osseointegration due to presence of CNTs in HA is quantified by the adhesion strength measurement of single osteoblast using nano-scratch technique. Considering the ongoing debate about cytotoxicity of CNTs in the literature, the present study also suggests boron nitride nanotube (BNNT) as an alternative reinforcement. BNNT with the similar elastic modulus and strength as CNT, were added to HA. The resulting composite having 4 wt.% BNNTs improved the fracture toughness (~85%) and wear resistance (~75%) of HA in the similar range as HA-CNT composites. BNNTs were found to be non-cytotoxic for osteoblasts and macrophages. In-vitro evaluation shows positive role of BNNT in osteoblast proliferation and viability. Apatite formability of BNNT surface in ~4 days establishes its osseointegration ability.