Papers by Author: Christiane Ribeiro

Abstract: Many techniques are used to assess biomaterials implants, always intending to measure osseointegration success and tissue response facing the implanted material. Calcium phosphates are widely used as biomaterial and a major component of bone. Many processing methods have been used to achieve porous materials to allow bone ingrowth with an osteoconductive scaffold for bone. To obtain the macroporous BCP implant it was processed by direct consolidation using the protein-action technique, a globular protein based consolidation with ovalbumin. The samples were sintered at 1250°C for 30 minutes, after sintering samples were cut in 4mm diameter cylinders, with 73% volume of porosity and mean pore size ranging about 100 µm. In the present work the macroporous BCP of HAp:β-TCP is assessed after bone implantation in rabbits tibia by lectinhistochemistry (LHC) technique. Lectins are proteins from non-imune origin which binds with strong specificity carbohydrates, LHC is a technique which mark histologically carbohydrates present in glycoproteins of cells. The macroporous BCP cylindrical samples were implanted in male rabbits tibia to the evaluation of biocompatibility and osseointegration in a period of 2 weeks to 4 weeks. After euthanasia of rabbits, tibia samples from the surgery site were taken and fixed with formalin, decalcified, dehydrated and embedded with paraffin to perform histological slides for both morphological and molecular evaluation. The morphological evaluation were performed on histological slides stained with Haematoxilin and Eosin (HE), while for molecular evaluation LHC was performed on histological slides using the lectins PNA, UEA-1, WGA, sWGA and RCA-1 (Vector Labs). All samples osseointegrated well with the bone and the neoformed bone surrounding the implant took the shape of its surface. The implants also allowed bone ingrowth inside the pores towards the center of implant, characterized by islets of round bone present in the HE stained slides.

Abstract: The potential of porous materials for applications in the medical, engineering and pharmaceutical areas has been widely reported. Several processing techniques have contributed to the progress in research involving porous biomaterials. To this purpose, a globular protein based (i.e. ovalbumin) consolidation approach has been proposed. In the present study, a porous hydroxyapatite: -tricalcium phosphate - biphasic ceramics (BCP), was processed by direct consolidation using the protein-action technique. The processed porous ceramic exhibited appropriate pore configuration in terms of size, morphology and distribution. BCP cylindrical samples were implanted in male rabbits tibia to the evaluation of the initial biocompatibility and osseointegration for a 30 days period. The morphological analyses, optical microscopy and scanning electron microscopy evaluated the osseointegration. A rough surface pattern displayed by the ceramics seemed to have improved cell adhesion and proliferation processes. Furthermore, the open porosity of samples was an essential requirement for a suitable bone-implant osseointegration. In conclusion, this study revealed that the porous matrices obtained, promoted suitable development for bone tissue growth and also properties for osseoconduction and osseointegration.

Abstract: In recent years, the processing of porous ceramic materials for implant applications has motivated the development and optimization of new technologies. To this purpose, a globular protein based (i.e. ovalbumin) consolidation approach has been proposed. In the present study, a porous hydroxyapatite:b-tricalcium phosphate - biphasic ceramics (BCP), was processed by consolidation using the protein-action technique. The processed ceramic materials exhibited appropriate pore configuration in terms of size, morphology and distribution. The in vitro reactivity and dissolution behavior of the ceramics was evaluated in SBF and biocompatibility in an osteoblasts culture, respectively. Overall, the materials tested showed biocompatibility and suitable properties for osteoconduction. A rough surface pattern displayed by the ceramics seemed to have improved both; cell adhesion and proliferation processes. In conclusion, this study revealed that the porous matrices obtained, promoted suitable development of cell metabolism without cellular death.

Abstract: Induction of an apatite-forming ability on a 100% Y2O3-ZrO2, 100% Al2O3, and 80/20 and 20/80 wt% of zirconia-alumina (Y2O3-ZrO2-Al2O3) composite polycrystals via chemical treatment with 5M H3PO4 have been investigated. The chemical treatments produced Zr-O surface functional groups, which are known to be effective for apatite nucleation in simulated body fluid. It’s believed that Al-OH surface functional groups are not effective for apatite nucleation. I this work was shown that apatite nucleates in substrate of alumina treat and untreated chemically. This implies that Al- OH functional groups are effective for apatite nucleation.

Abstract: In many in-vivo and in vitro studies, the behavior of calcium phosphate ceramics like β - tricalcium phosphate in biological environments has been reported to be predictive and positive. In terms of bone tissue growth, this ceramic can be more attractive presenting a porous microstructure. To obtain biomaterial quality ceramics, in this investigation β- TCP porous ceramics were prepared by a special consolidation method with albumin as a foam generating agent. This technique enables preparation a variety of formats with complex geometries. To obtain porous samples using albumin, heat had to be introduced into the system during the consolidation stage. After consolidation, the samples were sintered at 1250oC for 30 minutes and characterized using X-ray diffractometry, scanning electron microscopy and mercury porosimetry. The foams that were obtained by this method exhibited spherical and interconnected pores, characteristics desirable in biomedical implants.

Abstract: In the last years, the porosity in ceramic materials for implants production has motivated the development of various technologies. Calcium phosphate ceramics, in special the tricalcium phosphate - TCP, are very promising as bone substitutes and scaffolds for tissue engineering. The macroporosity incorporation in TCP ceramics by porogenic, foaming and consolidator agent, as globular protein (ovalbumin) was the focus of this work. Preliminary studies of zeta potential were made to have a suitable suspension. Ovalbumin amounts (5-7 wt%) were added to the ceramic slurries and suspensions with a solid percentage higher than 60 wt% were obtained. The interaction albumin/surfactant with detergency properties was evaluated by pH and viscosity measurements. The foam was produced by mechanical stirring. The results suggested that the presence of the surfactant increase the volume and stability of foam. After drying, burnout and sintering (1200oC/30 min.) the phase composition of the foams was determined by X-ray diffraction. The microstructure and porosity were evaluated by scanning electron microscopy. SEM micrographs of the foam show that the structure consists of a permeable porous network, being observed spherical and interconnected pores.