Biomedical subjects

Luis M Rodríguez-Lorenzo

Publications and source records attributed to Luis M Rodríguez-Lorenzo.

4 recordsLinked to original sources

PubMed2007

Development of wollastonite-poly(ethylmethacrylate co-vinylpyrrolidone) based materials for multifunctional devices.

The manufacturing of a composite made of a synthetic bioactive ceramic, pseudowollastonite (psW), and a bioresorbable copolymer ethylmethacrylate-vinylpyrrolidone (EMA/VP) is presented in this article. psW porous blocks were produced by dipping an open porous polyurethane foam in a psW containing slurry. A 40/60 wt % EMA/VP monomers mixture was poured on the blocks, and free radical polymerization initiated by azobis(isobutyronitrile) at 50 degrees C. Disks of 1 mm height were obtained by cutting the composite with a diamond saw, and bioresorption and bioactivity of the specimens were tested by immersion of the disks into SBF. A ceramic/polymer weight ratio of 72/28, greater than the usually achievable ratio by polymeric solidification of slurries of monomers charged with a powdered solid component, has been obtained. The system is bioactive and does not change the pH of the medium during the degradation test.

Biocompatible Materials↗

PubMed2004

Biodegradable composite scaffolds with an interconnected spherical network for bone tissue engineering.

Tissue engineering scaffolds are highly engineered structures that accommodate cells, facilitate their expression, and resorb to facilitate regeneration of tissue. A new technique for producing controlled pore shape and pore size interconnectivity offers promise for application as a tissue engineering scaffold. Salt particles were spheroidized in a flame and sintered to provide an interconnecting salt template. The salt template was filled with a carbonated fluorapatite powder and a polylactic polymer to produce a composite scaffold. It was found that a higher pore space is possible with the use of spherical and larger salt particle sizes. This technique can produce scaffolds with good interconnectivity and be suitable for producing pore size graded bodies.

Absorbable Implants↗

PubMedDate not supplied

Sintered hydroxyfluorapatites. Part I: sintering ability of precipitated solid solution powders.

The presence of fluoride within apatites occurring naturally within the body provides the basis for investigating the sintering ability of fluoride containing hydroxyapatites for use as biomaterials. Hydroxyfluorapatites were synthesized and then calcined to produce a 0%, 20%, 40%, 60%, 80% and 100% replacement of the hydroxyl ions with fluoride in the hydroxyapatite structure. Fluoride ion occupancy within the apatites was found to be about 90% of the anticipated value. Pycnometry results revealed a constant true density for powders of low to medium fluoride content followed by a rapid increase to the fluorapatite composition. Powders were uniaxially pressed, cold-isostatically pressed and sintered at 1150 degrees C, 1200 degrees C and 1250 degrees C. All hydroxyfluorapatite powders displayed a comparable ability for densification except when hydroxyl groups and fluoride ions were present at a comparable concentration. The grain size revealed that this composition also exhibited the smallest grain size and displayed the highest activation energy for grain growth. The lower diffusion created by similar amounts of fluoride and hydroxide within the lattice decreases grain growth and densification.

Biocompatible Materials↗

PubMedDate not supplied

Sintered hydroxyfluorapatites. Part II: mechanical properties of solid solutions determined by microindentation.

Fluoride substitution within hydroxyapatite is an important occurrence for biological apatites and is a promising approach for the chemical modification of synthetic hydroxyapatite. Limited information on the influence of fluoride substitution for hydroxyl groups on the mechanical properties has provided the rationale for this study. Hydroxyfluorapatites with 0%, 20%, 40%, 60%, 80% and 100% replacement of hydroxyl groups with fluoride ions were assessed for hardness, elastic modulus, fracture toughness and brittleness using microindentation of sintered pellets. The production of samples with a similar grain size and density allowed the influence of fluoride on mechanical properties to be determined. It was found that the hardness remains unaffected until 80% replacement of hydroxyl groups with fluoride, after which the hardness rapidly increases. The elastic modulus increases linearly with fluoride content. Fracture toughness is improved with fluoride incorporation into the lattice and reaches a peak of 1.8 for a 95% dense sintered pellet with a 60% fluoride replacement, followed by a rapid decrease at higher fluoride concentrations. The brittleness index is lowered to a minimum at 60%, after which a rapid increase occurs. High fluoride levels are unfavourable from a mechanical perspective, are not recommended for biomaterials, and can lead to a higher incidence of fracture where sodium fluoride, for treatment of osteoporosis, may produce a highly fluoridated hydroxyapatite.

Biocompatible Materials↗