Biomedical subjects

J M F Ferreira

Publications and source records attributed to J M F Ferreira.

13 recordsLinked to original sources

PubMed2007

Characterization and in vivo evaluation of sol-gel derived hydroxyapatite coatings on Ti6Al4V substrates.

Hydroxyapatite (HAP) based coatings on titanium alloy Ti6Al4V were attempted by sol-gel process. Precursor sol was dip-coated onto the substrates and the formation of HAP as the main phase was ensured after the sintering of coatings at 900 degrees C, as confirmed by the characterization studies involving XRD, FT-IR, Raman, and SEM-EDXS analysis. The biocompatibility of HAP-based coated titanium implants was tested by implantation studies in rabbit's tibia for a period of 8 weeks. Bone remodelling and inflammatory responses of the implants were studied during the implantation period. The better tissue-implant interaction of the coated implants with respect to the uncoated implants was observed after a defect healing period of 8 weeks. A coated implant with no evidence of rejection is a further advantage of the sol-gel derived HAP coating.

Alloys↗

PubMed2006

Fluorine-substituted hydroxyapatite scaffolds hydrothermally grown from aragonitic cuttlefish bones.

Porous hydroxyapatite scaffolds with different levels of fluorine substitution (46% and 85%) on the OH sites were produced via hydrothermal transformation of aragonitic cuttlefish bones at 200 degrees C and calcination at temperatures up to 1200 degrees C. The increasing level of F substitution reduces the kinetics and probably the yield of the reaction. The incorporation of F in the lattice of hydroxypatite caused a lowering of the unit cell volume due to reduction of the length of the a-axis. The crystallites formed were close in size to bone-like apatite and were orientated along the a-axis rather than the c-axis. There was evidence of AB-type carbonated apatite.

Animals↗

PubMed2006

Bond-coating in plasma-sprayed calcium-phosphate coatings.

The influence of bond-coating on the mechanical properties of plasma-spray coatings of hydroxyatite on Ti was investigated. Plasma-spray powder was produced from human teeth enamel and dentine. Before processing the main apatite coating, a very thin layer of Al2O3/TiO2 was applied on super clean and roughened, by Al2O3 blasting, Ti surface as bond-coating. The experimental results showed that bond-coating caused significant increase of the mechanical properties of the coating layer: In the case of the enamel powder from 6.66 MPa of the simple coating to 9.71 MPa for the bond-coating and in the case of the dentine powder from 6.27 MPa to 7.84 MPa, respectively. Both tooth derived powders feature high thermal stability likely due to their relatively high content of fluorine. Therefore, F-rich apatites, such those investigated in this study, emerge themselves as superior candidate materials for calcium phosphate coatings of producing medical devices. The methods of apatite powder production and shaping optimization of powder particles are both key factors of a successful coating. The methods used in this study can be adopted as handy, inexpensive and reliable ways to produce high quality of powders for plasma spray purposes.

Apatites↗

PubMed2006

Novel synthesis and structural characterization of fluorine and chlorine co-substituted hydroxyapatites.

Fluorine and chlorine co-substituted hydroxyapatites (HAP) were prepared through aqueous precipitation method. Characterization results from X-ray diffraction (XRD) revealed that co-substitution of these anions resulted in the formation of pure HAP phase except for the small observed difference in the lattice parameters of the resultant apatites. The elemental analysis and FT-IR results have also confirmed the incorporation of substituted anions in the apatite structure. The calculated crystallite size for all anionic substituted apatite fall well below the range of 50 nm size that tend to coincide with the value of bone mineral crystallite size.

Chemistry, Inorganic↗

PubMed2006

Hydrothermal growth of hydroxyapatite scaffolds from aragonitic cuttlefish bones.

Scaffolds of AB-type carbonated hydroxyapatite (HA) were successfully produced via hydrothermal transformation (HT) of aragonitic cuttlefish bones at 200 degrees C. The transformation was seemingly complete after 9 h of HT and no intermediate products were registered. Beyond low production cost, worldwide availability, and natural-biological origin of raw materials, the produced scaffolds preserved the initial structure of cuttlefish bone, featuring good biocompatibility in osteoblasts tests and ideal pore size ( approximately 80 microm in width and approximately 100 microm in height) and interconnectivity for supporting biological activities, such as bone tissue growth and vascularization. The highly channeled structure and the use of fresh cuttlefish bones favored the diffusion of the reaction solution towards the aragonite resulting in fast kinetics (after 1 h, hydroxyapatite was the dominant crystalline phase).

Animals↗

PubMed2005

Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

Biocompatible Materials↗

PubMed2005

Scaffolds for bone restoration from cuttlefish.

Scaffolds of pure hydroxyapatite suitable for either direct clinical use or tissue-engineering applications were successfully produced via hydrothermal transformation of aragonite, obtained from fresh cuttlefish bones, at 200 degrees C followed by sintering. Beyond low production cost, worldwide availability and natural-biological origin of raw materials, the produced scaffolds have ideal pore size and interconnectivity features suitable for supporting biological activities, such as bone tissue growth and vascularization. Bioactivity in vitro tests were excellent: (a) rapid and pronounced formation of hydroxyapatite occurred when the scaffolds were immersed in simulated body fluid (SBF), and (b) outstanding proliferation of osteoblasts was registered. The produced scaffolds can be machined and shaped very easily at any stage of processing. Therefore, these ceramic scaffolds can satisfy both bioactivity demands and the requirements for shaping of tailor-made individualized implants, especially for randomly damaged bones.

Animals↗

PubMed2004

Temperature-induced gelation of concentrated silicon carbide suspensions.

Due to the steric barrier provided by the adsorption of the dispersant hypermer KD1 (a polyester/polyamine condensation polymer), stable and low-viscosity suspensions of SiC, Y(2)O(3), and Al(2)O(3) powder mixtures could be prepared in methyl ethyl ketone (MEK)/ethanol (E) solvent with solids loading as high as 60 vol%. The solvency of the dispersant in MEK/E decreased dramatically on cooling. Steady shear viscosity and oscillatory measurements were performed as a function of temperature for suspensions with different solids loading. The viscosity and elastic modulus of suspension increased with decreasing temperature and became more sensitive with the increase of solids loading. The suspensions with solids loading higher than 40 vol% could be solidified with decreasing temperature, but gelation temperature and gelation stiffness decreased with decreasing solids loading. The 60 vol% solid-loaded suspension was a stable and free-flowing fluid at 20 degrees C and gradually transformed to a very highly viscous and elastic system upon cooling to about 13 degrees C. Complete solidification occurred when the temperature was decreased to 5 degrees C. The gelation mechanism was mainly based on the collapse of the adsorbed layer as the temperature decreases, which induced incipient flocculation and formed a stiff network. The gelled body was further strengthened by separation of the dispersant from the suspension.

Carbon Compounds, Inorganic↗

PubMed2004

Surface modifications of alumina-silica glass fiber.

A commercial glass fiber with Al(2)O(3) (68.4%) and SiO(2) (27.6%) as major components and CaO, TiO(2), Fe(2)O(3), and CuO as minor components was used as substrate in a silica sol-gel coating process. After cleaning, fiber samples were immersed into tetraethoxysilane (TEOS) at room temperature for 1 h, and then individual fiber samples were soaked into a simulated body fluid (SBF) solution,1 and removed after 5, 10, 15, and 20 days. Zeta potential and Energy Dispersive Spectroscopy (EDS) analyses showed that the fiber surfaces were effectively coated with a silica layer, which improved the formation of an HA layer upon immersion into SBF solution for 5 days. The coating became even more continuous after 10-day immersion. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P--O vibration bands characteristic of hydroxyapatite (HA) near 1060 and 600 cm(-1).

Aluminum Oxide↗

PubMed2004

Sol-gel preparation and in vitro test of fluorapatite/hydroxyapatite films.

Fluorapatite/hydroxyapatite (FA/HA) films have been demonstrated to be a good alternative to pure hydroxyapatite (HA) ones in medical applications because of their bioactivity and relatively low solubility. In this study, Ca(NO(3))(2), P(2)O(5), and HPF(6) were used to prepare FA/HA films on Ti6Al4V substrate with the use of a sol-gel method. The F contents in the films could be tailored by adjusting the amount of HPF(6) added. The in vitro evaluation of the films was carried out in both SBF9# solution and TRIS buffer solution. The films with appropriate F contents showed a better ability to induce calcium phosphate deposition on their surfaces than either pure HA film and FA/HA films with even higher F content, as well as smaller dissolution amounts than HA film in TRIS buffer solution. Hence, the FA/HA films obtained in this work integrate both good bioactivity and stability, and could be a better choice for bioactive film on titanium alloys to produce high-quality implants.

Apatites↗

PubMed2003

Controlling hydrolysis and dispersion of AlN powders in aqueous media.

Aqueous suspensions of aluminum nitride (AlN) powders have been prepared in the presence of different surface-active agents, namely, H3PO4 and an anionic surfactant, to avoid the hydrolysis of AlN powders and to enhance dispersion. The most determinant parameters to the hydrolysis process (DeltapH and time of contact) and the stabilization of AlN particles in water (surface crystallinity, surface chemical modification, and surface ionic charge) were seen to be strongly dependent on the acidic agent. The H3PO4 treatment was effective against hydrolysis of AlN due to the formation of a phosphate-based protection layer on the particles' surface, and, although it keeps the pH of the suspension below 4, it does not guarantee a good dispersion. The individual adsorption of the anionic surfactant at the surface of AlN particles suspensions did not completely suppress the hydrolysis but it did enhance the degree of dispersion. A proper combination of the two types of surface-active agents enabled the preparation of AlN aqueous suspensions of relatively low viscosity and high AlN concentration, which can be a good starting point for aqueous-based colloidal shaping techniques or for freeze granulation or spray drying to obtain suitable granulate powder characteristics for dry-pressing technologies. An adsorption mechanism of the surface-active agents onto the particles' surface is proposed and supported by NMR and FT-IR analyses.

Journal Article↗

PubMed2002

Fabrication of porous hydroxyapatite bodies by a new direct consolidation method: starch consolidation.

A new direct consolidation method known as "starch consolidation" was developed especially for the fabrication of porous ceramics, as adopted to prepare hydroxyapatite (OHAp) bodies with different pore sizes and pore volume fractions. The method is based on the swelling ability of starch when it is heated to 80 degrees C in the presence of water. An OHAp powder prepared by a precipitation method and heat treated at 900 degrees C to obtain an appropriate specific surface area for colloidal processing was used in the present work. Wet ball milling was required to deagglomerate the powder and improve its processing ability. Different starch volume fractions and starch particle sizes were added to the OHAp slurries, which were then heat treated to promote consolidation by starch gelification. A linear relationship between the planned and measured porosity values was observed. SEM pictures reveal the presence of interconnected pores with shape and sizes corresponding to starch granules used. Flexural strength varied from about 2 to 15 MPa, for pore volume fractions of approximately 70 and 45%, respectively. A degradation study in an acellular synthetic body fluid (SBF) has shown that the prepared bodies keep their integrity under physiological conditions during the studied time. The method offers possibilities of manufacturing materials that can be used as scaffolds engineering and/or systems for controlled delivery of drugs.

Adsorption↗

PubMed2002

Hydroxyapatite ceramic bodies with tailored mechanical properties for different applications.

A perfect control on the final ceramic features will enable the research/clinical community to spread the use of calcium phosphate ceramic bodies to a large number of applications and/or requirements. The mechanical properties of hydroxyapatite ceramic bodies manufactured by different techniques and with different porosities is presented. The flexural strength, hardness, fracture toughness, surface roughness, and their evolution after immersion in SBF are studied. An increase of the mechanical properties with density is observed. The factors governing these results are analyzed. The increase of the porosity percentage of the bodies results in an increase on the surface roughness. The degradation studies show that the HA ceramics keep their integrity and mechanical properties under physiological conditions during the soaking time studied. The OHAp ceramic bodies with controlled porosity could be appropriated for hard tissue substitution or as a carriers for controlled delivery of drugs or as scaffolds for tissue engineering.

Algorithms↗