Bioceramics are used to repair, rebuild, and replace parts of the human body, e.g., bones, joints and teeth, in the form of powder, coatings or prostheses. The synthetic hydroxyapatite [Ca10(PO4)6(OH)2 (HAP)] based on calcium phosphate has been widely used in the medical and dental areas due to the chemical similarity with the inorganic component of human bone tissue. In this work, hydroxyapatite nanocrystalline powders were synthesized by the solid-state reaction method and sintered with a galactomannan and chitosan blend. The bioceramics studied were prepared from 70%, 80% and 90% of hydroxyapatite with 30%, 20% and 10% of galactomannan and chitosan blends, respectively. The influence of the blend content on the bioceramics was investigated through structural, vibrational, thermal, morphological and dielectric characterizations. It was observed that the increase in the blend percentage promoted an increase in the grain size, which was followed by a decrease in the density and hardness of the samples. The sample with a higher amount of polymeric blend also presented a higher dielectric constant and higher losses.

In the last decades there has been a extraordinary evolution in the area of Dentistry, especially in Implantology. Given the aesthetic and functional requirements of an increasingly demanding society, there is often the need to resort to reconstructive surgeries, which allow the regeneration of bone tissue once lost. Biomaterials, both from human, animal or synthetic origin, have been used as bone replacement for implants. They intend to mimetize the bone physiology, act as a support and potentiate the formation of new tissue, without inducing immune response.The present thesis is included in a wider project intending to fill in bone defects for Dentistry. The main objective has been to evaluate the cytotoxicity of different scaffold formualtions, sterilized with different common techniques. These scaffolds were produced by an additive manufacturing technique, consisting of poly(caprolactone) (PCL) or PCL and hidroxyapatite (HA). They were manufactured not only with different levels of HA (10% or 25%), but also from two different origins: natural and synthetic. Regarding their structural composition, scaffolds are formed by filaments which thickness varies between 300 and 600 m, and with an angle variation between filaments of 0º/90º and 0º/45º. The goal of such scaffolds, with distinct formulations and architectures, steilized by the three most used methods of sterilization in clinics, namely ethlyene oxide, gamma radiation and plasma, was to infer which combination would have the greatest influence on biological performance, correlated with the sterilization process.The different scaffolds were sterilized and evaluated through microbiological assays, to confirm the effectiveness of the sterilization method. The results of these tests confirmed the absence of microbial growth, showing that the results are in compliance with the current rules.When tested in vitro, as support for fibroblast, macrocytic, and their co-culture, an uniform cell distribution throughout the scaffold was observed, indicating an affinity for these structures.In order to comprove the integration process in vivo some of the scaffolds, those obtaining the best and the worst results in vitro, were selected. After 1 month post implantation, the integration process was evaluated, by macro and microscopic observation. Regarding the cicatrization process and inflammatory reaction the results indicate that they proceeded as expected, obtaining a good healing. This suggests a good integration verified by the histological technique.Attempting to obtain stem cells for further differentiation into bone-like producing cells, from young dental pulp and aplical papilla, explant culture assays were performed. However, it was not possible to obtain these results in order to proceed further with cell differentiation. The results of the in vitro tests allowed to refine the selection of the best formulations, promoting the regeneration of bone defects in the oral cavity. It has been shown that sterilization methods are directly correlated with the formulation and duration of the study.

As lesões da coluna, nomeadamente as fraturas por compressão em vértebras osteoporóticas, incentivaram o desenvolvimento de técnicas cirúrgicas sofisticadas, acompanhadas por progressos importantes em biomateriais para reparação óssea. Presentemente, a cifoplastia constitui um dos métodos mais avançados no tratamento e reparação de vértebras fraturadas. Trata-se de uma técnica minimamente invasiva que consiste na injeção percutânea de um cimento ósseo no corpo vertebral colapsado, após a sua altura ter sido restaurada por meio de um balão insuflado no seu interior. Após ser injetado, o cimento ósseo solidifica, conferindo assim maior resistência à vértebra reparada. Tipicamente, os cimentos ósseos utilizados são materiais poliméricos como o poli(metilmetacrilato) (PMMA), ou outras composições baseadas em acrilatos, cujo mecanismo de ação consiste numa reação de polimerização que permite a obtenção de uma pasta injetável e endurecível in situ, num curto período de tempo. A preparação do cimento ósseo envolve a mistura dos reagentes momentos antes da sua injeção e a sua aplicação é monitorizada através de técnicas radiológicas. Genericamente, este tipo de cimentos ósseos é considerado eficaz e seguro para aplicação em cifoplastia. Porém, permanecem diversos fatores de risco e limitações que, embora tenham a vindo a ser minimizados ao longo do tempo, justificam a investigação de novos biomateriais para esta técnica cirúrgica. O presente trabalho centrou-se na pesquisa por um novo biomaterial para aplicação em cifoplastia, com o objectivo de obter uma alternativa viável e propriedades materiais superiores às dos cimentos ósseos comercialmente disponíveis, sobretudo baseados em PMMA. Pretendeu-se desenvolver um sistema injetável que, após solidificação nas condições fisiológicas do interior de uma vértebra, originasse um material compósito com composição e algumas propriedades semelhantes às do tecido ósseo. Como ponto de partida, pretendeu-se que a fase inorgânica do compósito incluísse componentes minerais baseados em hidroxiapatite natural, obtida a partir de osso, e um agente de contraste radiológico, tendo sido selecionado sulfato de Bário. Na fase orgânica do compósito, pretendeu-se utilizar poli (álcool vinílico), um polímero sintético hidrossolúvel, como constituinte principal de um sistema polimérico adequado à solidificação in situ. Este polímero permitiu obter suspensões homogéneas dos minerais selecionados; no entanto a escolha de reagentes reticulantes constitui um grande desafio. Esta investigação envolveu o teste de múltiplos reagentes, originais ou manipulados, e o estudo de combinações que não tinham sido antecipadas no início dos trabalhos. Estes testes exigiram uma multiplicidade de técnicas experimentais que culminaram numa formulação capaz de satisfazer os requisitos químicos, físicos e mecânicos previamente definidos. Obteve-se um pré-compósito baseado numa suspensão de minerais em solução aquosa de poli (álcool vinílico) modificado com uma carbodiimida, à qual se adicionou colagénio hidrolisado em meio alcalino e ainda persulfato de potássio. Para solidificar esta mistura e obter um material compósito, recorreu-se a 2-hidroxietilmetacrilato. Os ensaios in vitro mostraram que os compósitos obtidos eram biocompatíveis com osteoblastos humanos e a sua ação hemolítica não era significativa. Adicionalmente, desenvolveram-se microcápsulas biodegradáveis com composição e estrutura específicos, com o objetivo de funcionarem como dispositivos de libertação de fármacos, ou de outras substâncias, contribuindo simultaneamente para a criação de porosidade adequada no compósito. As microcápsulas foram utilizadas para libertarem o agente reticulante na suspensão do pré-compósito. Realizou-se um ensaio in vivo com modelo animal e confirmou-se que o contraste radiológico do compósito era adequado. A análise histológica mostrou que o compósito implantado era biocompatível e possuía propriedades osteocondutoras e osteoindutivas. Este projeto conduziu à obtenção de biomateriais com propriedades moduladas à estrutura e à função, bem como à sua aplicação clínica em cifoplastia. Após adicionar o agente reticulante à suspensão de pré-compósito, a mistura permanece injetável e pronta a aplicar. A solidificação gradual in situ, no defeito ósseo, é acompanhada pela absorção dos fluidos circundantes, levando a um aumento de volume do compósito. Consequentemente, o defeito ósseo fica com melhor preenchimento e maior contacto interfacial com o tecido ósseo. A porosidade do biomaterial com microcápsulas adicionadas pode contribuir para a regeneração óssea.

Ti-HAP biocomposites are gained attention for combining the attractive properties of Ti and hydroxyapatite (HAP). However, the decomposition of HAP at elevated processing temperatures is a major concern since it can lead to structural flaws and may deteriorate the corrosion resistance of Ti. The present study aims to investigate the corrosion behavior of Ti-HAP composite processed by powder metallurgy by performing potentiodynamic polarization and electrochemical impedance spectroscopy in 0.9wt% NaCl solution at body temperature. Results show that the presence of Ti lowers the HAP decomposition temperatures resulting in the formation of HAP-depleted zones acting as electrochemically active sites, decreasing the corrosion resistance.

Abstract In the present study, hydroxyapatite and Zn-substituted hydroxyapatite powders were synthesized using ostrich eggshell as a calcium source. The samples were analyzed by scanning electron microscopy with field emission gun, and X-ray diffraction (XRD) to identify the present phases, and X-ray fluorescence spectroscopy for quantitative chemical analysis of the synthesized and heat treated powders. The Fourier transform infrared spectroscopy technique was used before and after heat treatments at 700, 900 and 1100 °C in order to identify the functional groups present, as an additional technique to the XRD analysis. The results presented in this study represent a promising method for synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc, since the results showed no undesirable phases or impurities in the produced powders. It was observed that Zn-substituted hydroxyapatite showed higher thermal stability, when compared to pure hydroxyapatite.

Bioactive materials possess properties that allow them to interact with natural tissues to induce reactions that favor the development and regeneration of those tissues. In this study, silica was prepared by the sol-gel method, using tetraethylorthosilicate as the precursor. The calcium and phosphor sources used here were calcium ethoxy and phosphoric acid, respectively, in ethanol solvent. The solid obtained was dried at 50 ºC. In vitro bioactivity assays were performed by soaking the materials in simulated body fluid (SBF). The samples were characterized by transmission electron microscopy (TEM), thermal analysis and photoluminescence. TEM images of the samples before contact with SBF revealed amorphous aggregates and after 12 days in SBF showed two phases, one amorphous with large quantities of Si and O, and the other a crystalline phase whose composition contained Ca and P. The electron diffraction pattern showed a planar distance of 2.86 Å, corresponding to 2θ = 32.2º. This was ascribed to hydroxyapatite. The Eu III was used as structural probe. The relative band intensity correspondent the transition 5D0 → 7F2 / 5D0 → 7F1 showed a high symmetry surrounding the Eu III ion. These materials, produced by the sol-gel route, open up new possibilities for obtaining bioactive biomaterials for medical applications.

Abstract The composite materials using polyhydroxybutyrate as matrix and hydroxyapatite as reinforcement (PHB/HA) were produced by molding, using pressing at 100 MPa and 165 °C for 30 min. The amount of filler was varied from 0 to 20 wt% to evaluate the effect of the HA particles on mechanical properties and the bioactivity of the composites. The increase of the HA amount reduced the compressive strength of the composites nearly 20% while bending strength reduced nearly 30%. However, the bioactivity after 14 days immersion in SBF was improved with the increase of HA amount, with formation of apatite layer on the surface of the PHB/HA composite.

Abstract Characterization of both uncalcined and calcined eggshells was done in this work. Raw eggshells turned out as a good source of calcite phase. Calcined eggshells had a mixture of lime and portlandite phase. A significant impact of calcination temperature on the percentage of generated phases was observed. Qualitative as well as semi-quantitative phase analysis, morphological characterization and physical property estimation was done for the produced powder. The influence of synthesized raw material on soil stabilization and biomaterial formation was further assessed. The eggshell turned out as a potential source of raw material for various sectors.

Abstract A ceramic/polymer biocomposite with high potential for multifunctional practical applications in bone tissue engineering was synthesized by using a well-known piezoelectric polymer, polyvinylidene fluoride (PVDF), and a high bioactive biphasic calcium phosphate (BCP) ceramic obtained from recycled fish bones. High-bioactivity was observed for the PVDF-BCP composite when it was subjected to conditions that simulate the animal body once a very thick apatite layer (9 μm) was grown on its surface in an immersion experiment (7 days) in simulated body fluid. The structural characteristics of the PVDF-BCP composite showed similarities with highly bioactive young animal bones, overlapped with PVDF polymorphic phases. Mechanical tests revealed properties very similar to those of the human bone tissue with a resistance strength reaching 80 MPa. Together, all these factors indicated a very promising material for application in osseous implants/replacement with postoperative recovery controlled/accelerated by external stimuli.

Abstract The hydroxyapatite (HAp) is a ceramic biomaterial with wide application in the bone regeneration. It can be obtained by different routes and different precursors. In this study, the synthesis of HAp was carried out by precipitation and subsequent thermal treatment using different calcium precursors: calcium hydroxide from synthetic origin and calcium oxide obtained from the eggshell. The obtained materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. By SEM, variations of the crystal size and the concentration of agglomerates were observed. FTIR and XRD analyses proved the formation of HAp and how the (mineral and biological) precursors affected the microstructure. The thermal decomposition process of the calcium oxide obtained from the eggshell showed to be more effective for the synthesis of the hydroxyapatite, resulting in more stable morphology and microstructure.