Papers by Author: Cecília A.C. Zavaglia

Abstract: Along decades, bioceramics have been used as materials for bone reconstruction, where hydroxyapatite is one of the most used bioceramics. But hydroxyapatite mechanical strength is not so high when compared with another bioceramics. This research aimed to characterize hydroxyapatite-titanium oxide scaffolds with different compositions. Samples were made using a polyurethane sponge with compositions of 70%-30% wt., 60%-40% wt. and 50%-50% wt. of hydroxyapatite-titanium oxide, calcined at 550°C for burning the polymeric sponge and sintered at 1250°C, 1300°C and 1350°C. Samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). Results showed that all compositions maintained the polymeric sponge pores structure without any residual traces of the polymeric sponge. Those results are in accordance with technical literature and it is indicated to do in vitro essays to study the scaffolds biocompatibility for using as bone reconstruction materials.

Abstract: An application of calcium phosphates is as bone cements, among which the system based on alpha-tricalcium phosphate (α-TCP) exhibits excellent properties. The aim of this study is to analyze pH evolution and cytotoxicity of α-TCP cement with three different additives. Changes on the pH were measured at intervals of 12h during seven days. But initial measurements were executed at each 15 minutes. Indirect cytotoxicity test was performed according to ISO (10993-5, 1992) employing CHO-k1 cells and RPMI 1640 as culture medium. It was used a colorimetric method which uses the tetrazolium compound. The additives used on the liquid phase were disodium hydrogen phosphate (Na₂HPO₄) and/or citric acid (C₆H₈O₇) and/or tannic acid (C₇₆H₅₂O₄₆). The results indicate that the cement without additives does not have requirements to be applied like bone cement, while the other cements composition exhibit different responses in the pH and the cytotoxicity test. In conclusion, due to the presence of additives it was possible to control pH evolution during setting and cytotoxic response. However, further investigation is necessary in order to determine the influence of these additives, mainly tannic acid, on the in vivo behavior of these bone cements.

Abstract: Among the calcium phosphate cements, the system based on alpha-tricalcium phosphate (α-TCP) combines several interesting properties. However, these cements have their use limited to low load applications. The main objective of this study is to evaluate the influence of three different additives on the setting reaction kinetics and mechanical strength evolution of calcium phosphate cements as a function of time. The cement was obtained by mixing α-TCP powder with four different aqueous solutions containing or not containing disodium hydrogen phosphate (Na₂HPO₄), citric acid (C₆H₈O₇) and/or tannic acid (C₇₆H₅₂O₄₆). It was observed that two cement samples, one of them containing Na₂HPO₄ and C₆H₈O₇ and another containing Na₂HPO₄ and C₇₆H₅₂O₄₆ in the liquid phase, presented faster setting reaction and higher mechanical properties. These cements are more suitable for application as bone cement.

Abstract: Orthopedics surgeries frequently are open surgeries, but the improvement of the specific instrumentation and the use of bioresorbable polymerics implants for regeneration of bone fractures are contributing to the development of noninvasive techniques such as an injectable bone substitute. These injectable materials are composites, formed by a particulate ceramic phase and a polymeric phase, and have the advantages of combining bioactivity and the ability to control degradation and some mechanical properties. In addition, microparticles present flexibility to fill several types of defects with closer packing and allow new bone growth and vascularization through the interconnected pores formed by the spaces between them. Another advantage of the particulate materials is that they have the potential to incorporate drugs such as antibiotics that can be applied in situ for treatment or prevention of bone infection, which is important because the poor circulation of blood in the osseous tissues makes necessary large amounts of these drugs to guarantee that an adequate dose reaches the affected site. This work evaluates the release potential of gentamicin from BCP spherical microparticles to be used in osseous injectable implants. The particles present a smooth geometry to prevent inflammatory reactions frequently caused by an irregular morphology, and their compositions offer a combination of biodegradability and stability. Microparticles with diameters between 150-425µm, were obtained by a method based on the immiscibility of liquids. To encapsulate the antibiotic, the spheres were immersed in a gentamicin solution, and after 24h they were separated and dried. The evaluation of the gentamicin release from the microspheres was carried out at 37°C in PBS, and the release medium was collected at predetermined time intervals for measurement of the amount released. This work demonstrates that these microspheres can find potential application in bone repair and regeneration.

Abstract: Titanium dioxide is a material widely used in electronics industry and little explored in the biomedical area, which is the objective of this work. Nowadays one can find surgical instruments coated with thin films that have bactericidal properties when they are activated in the presence of ultraviolet light. For crystalline phase control TiO₂ was calcinated at 500°C. The crystallite mean size for sample calcinated at 500°C was 27nm. With the results of cytotoxicity it is possible to say that biomedical applications are possible. Electron microscopy images showed nanoparticles obtained by sol-gel process and the compounds were identified by FTIR analysis. Raman spectroscopy confirmed the existence of anatase titania phase and X-ray diffraction showed this material to be composed of a crystalline phase. X-ray fluorescence identified chemical contaminants.

Abstract: Particle size is one of the most important factors to the successful application of calcium phosphate bioceramics as it may have an important role on its final properties such as mechanical resistance and reactivity. Thus, a process which results on very small and homogeneous particles is required, since it avoids further contamination derived from long milling times. On this context, a process such as sol-gel synthesis may be feasible, due to its simplicity on handling and its well known characteristic of producing homogeneous nanoparticles. Moreover, precipitated HA also may lead to satisfactory results regarding particle size and phase purity. The aim of this article was to demonstrate a preliminary characterization study of powders obtained by both methods and to compare them to a commercial sample available in Brazil. Characterization was made by XRD, Scherrer’s equation, XRF, SEM-LV, SEM-FEG and SEM-EDS. It has been found out that all samples consist of pure nanostructured hydroxyapatite with crystallite size between 37nm and 62nm.

Abstract: Biocompatible fibers has been studied and synthesized in order to improve the mechanical and general properties of bone cements. In order to do so, this work presents the synthesis of Whisker-like fibers of Silicon doped Hydroxyapatite by alkaline hydrolysis of Silicon doped α-TCP. The main fibers analyzed by SEM showed an aspect ratio of about 18 (l = 3.9 µm, d = 0.22 µm), well defined superficial aspect and hexagonal structure. XRD and EDX characterization presented Calcium Deficient Hydroxyapatite peaks and Ca/P ratio of 1.47.

Abstract: A lot of attention has been given to bone cements due to their lack of mechanical properties. The improvement of this property is essential, once it makes possible the usage of these biomaterials in sites that require a significant mechanical strength resistance. To do so, reinforcement agents, such as fibers, in particular biocompatible fibers, have been synthesized [1]. This study reports the synthesis of stequiometric Hydroxyapatite whisker-like fibers utilizing the Molten Salt Synthesis process of nanometric Hydroxyapatite with a salt flux mixture of KCl/NaCl. According to SEM images, EDS analysis and X-ray diffraction, the fibers obtained presented well defined and elongated (main length of about 70µm) hexagonal morphology with Ca/P ratio of 1.66.

Abstract: The Tissue Engineering appears with a modern proposal for the treatment of damages or diseases. The study of materials and methods for tissues and organs regeneration by the patient cells culture had been developed on the last years but still couldn’t be used for all different tissues. In this multidisciplinary research field, the present work joins the biodegradability of poly(ε-caprolactone) (PCL) with the osteoconductive properties of β-tricalcium phosphate (β-TCP) in order to create a composite which acts as a temporary support for cell culture without a second surgery to remove the biomaterial. This work evaluates three membranes types, obtained by casting in chloroform, on the biocompatibility and differentiation on mesenquimal stem cells (hMSC). These analyses showed cell viability with the rezasurin method and the alkaline phosphatase activity (ALP). DMA analyses, MEV and OPM were performed.

Abstract: On this study the influence of silicon dopping on the properties of the final calcium phosphate cement were analysed and compared to the ones of the conventional Si and Mg-free α-TCP cement. In spite of silicon doping, Si-α-TCP calcination temperature (1400°C) was higher than the one used for conventional α-TCP (1300°C) as a result of Mg contamination on the commercial precursor used on the Si-α-TCP synthesis. Because of the high temperature used, Si-α-TCP sample was difficult to mill. Even after 1 week milling, the particle size achieved was 12µm while Si-free α-TCP reached 7.7µm. Consequently, the reactivity of both powders was different. In conclusion, the properties of Si-α-TCP cement were not satisfactory for clinical application. In order to do it so, it is essential to enhance the powder reactivity by reducing Mg contamination, lowering the sintering temperature and reducing the particle size to, then, achieve the desired reactivity and compressive strength.