Anita Lucas-Girot

In vitro bioactivity of melt-derived glass 46S6 doped with magnesium

Melt-derived glasses in the system SiO(2)-CaO-Na(2)O-P(2)O(5) were synthesized pure or doped with magnesium from 0.4 to 1.2 wt %, for applications as biomaterials in bony surgery. This chemical element has been chosen because of its high physiological interest. Its introduction for different contents in melt derived glasses has never been studied. The bioactivity of glasses was assessed by immersion of the samples in the simulated body fluid solution. Changes in glass surface morphology and composition after immersion were evaluated by several physico-chemical techniques. The aim of this work was to characterize the formation of the apatite-like layer at the glass surface, after in vitro assays and to evaluate the kinetic reaction between the glass and the surrounding synthetic fluids. Results indicate that magnesium influences the formation and the evolution of the newly formed layers: (1) it promotes the dissolution of the silica network, (2) it increases the thickness of the silica gel layer formed conventionally prior to the apatite-like layer, and (3) it slows down the crystallization of the apatite layer. However, the intensity of these effects depends on the content of magnesium introduced in the glass matrix.

A synthetic aragonite-based bioceramic: influence of process parameters on porosity and compressive strength

We investigate the influence of process parameters such as weight fraction and particle size of pore-former, and isostatic pressure, on porosity and compressive strength of non-sintered porous calcium carbonate biomaterials compacted at high pressure in uniaxial or isostatic mode. Experiment design and results analysis are performed according to a two-level 2k factorial design method (FDM). Results indicate that only the weight fraction of pore-former (wt fpf) influences significantly the porosity and the compressive strength. The porosity P, is described by a linear function of wt fpf, and the compressive strength sigma(comp), by an exponential one. For materials compacted under uniaxial pressing: P (vol%) = 33.7 + 85.4 (wt fpf) and sigma(comp) (MPa) = 28.8e(-9.2(wt fpf)) with 0.1 < or = wt fpf < or = 0.3. For materials compacted in isostatic mode: P (vol%) = 33.9 + 82.1 (wt fpf) and sigma(comp) (MPa) = 24.0e(-7.0(wt fpf)) with 0.15 < or = wt fpf < or = 0.35. The pore-former particle size has no significant influence on both properties. The increase in isostatic pressure provides slightly lower porosity and better compressive strength. For a fixed fraction of pore-former, isostatic pressing leads to a better compressive strength than uniaxial pressing. This study indicates that, for a constant amount of pore former, the size of macropores can be adjusted to reach optimal bone-ingrowth without change in compressive strength.

Thermal behaviour of composites aluminosilicate-calcium phosphates

A new type of aluminosilicate matrix calcium phosphate crystallites composites (ACPC) was synthesized and studied for osseous bone applications. The room temperature synthesis of the aluminosilicate matrix and composites was described. Thermal treatments of compounds allowed the adaptability of some parameters (pH, porosity and mechanical properties). Structure of heat treated composites were characterized by XRD and FTIR. The influence of thermal treatment on the mechanical properties, the porosity and the pH was studied for two temperatures (250 and 500°C). Results evidenced the ability to control the pH, the high level of porosity (»70%) and the good mechanical properties, allowing to consider that ACPC are potential biomaterials for osseous bone application.

Physical and biological characteristics of nanohydroxyapatite and bioactive glasses used for bone tissue engineering

Abstract Critical-sized bone defects have, in many cases, posed challenges to the current gold standard treatments. Bioactive glasses are reported to be able to stimulate more bone regeneration than other bioactive ceramics; however, the difficulty in producing porous scaffolds made of bioactive glasses has limited their extensive use in bone regeneration. On the other hand, calcium phosphate ceramics such as synthetic hydroxyapatite and tricalcium phosphate are widely used in the clinic, but they stimulate less bone regeneration. This paper gives an overview of the recent developments in the field of bioactive nanoparticles, with a focus on nanohydroxyapatite and bioactive glasses for bone repair and regeneration. First, a brief overview of the chemical structure and common methods used to produce synthetic nanohydroxyapatite and bioactive glasses has been presented. The main body of the paper covers the physical and biological properties of these biomaterials, as well as their composites with biodegradable polymers used in bone regeneration. A summary of existing challenges and some recommendations for future directions have been brought in the concluding section of this paper.

Excess entropy and thermal behavior of Cu- and Ti-doped bioactive glasses

Bioactive glasses belong to the ceramic family. They are good materials for implantation due to their excellent capacities to create an intimate bond with bones. Copper is known for its anti-inflammatory, antibacterial, and antifungal properties. Titanium is biocompatible and resistant to corrosion. These chemical elements can be introduced in bioactive glasses to provide a wide variety of uses and to enhance the physiological properties of implanted biomaterials. In this work, bioactive glasses doped with different contents of copper and titanium were synthesized by the melting method. The purpose is to study the effect of doping metal element on the thermal characteristics (Tg, Tc, and Tf). The results revealed that the increase of the content of copper and titanium in the glass matrix decreases the melting temperature and induces an increase of the thermal stability. The excess entropies of pure and doped glasses were calculated. Obtained results highlighted the decrease of the excess entropy with the increase of metal elements contents.

Effect of Copper and Zinc on the Bioactivity and Cells Viability of Bioactive Glasses

Bioactive glasses, doped with traces of copper (Cu) and zinc (Zn) were synthesized by fusion method. Cu and Zn present interesting functions for the biological metabolism through their antibacterial, anti-inflammatory and antifungal properties. Several physical methods were employed to characterize the bioactive glasses before and after immersion in a Simulated Body Fluid (SBF). The “in vitro” experiments showed that after soaking in SBF, the behavior of bioactive doped glasses are different compared to pure glass 46S6. Obtained results show that glass matrix undergoes some changes after 15 days of immersion. The non toxic character of doped glasses was confirmed after 24 hours of incubation. The kinetic of release of Cu and Zn was carried out. It highlights that Cu is more released than Zn. By SEM, the morphology of hydroxyapatite obtained with Zn-doped glass show a better crystallization compared to Cu-doped glass.

Comparison of the bony remodelling of two synthetic biomaterials: aragonite 55% and aragonite 55% with active substance

In this work, the in vivo behaviour of pure aragonite and vectabone, which is an association of aragonite and an active substance such as gentamicin, was studied to highlight the kinetic resorption of these two biomaterials with 55% of porosity destined for the filling or replacement of bony defects. The synthesis conditions and parameters we used permit us to obtain a biomaterial without a sintering stage. These conditions allow introducing of active substances at the first stage of the elaboration. In this work, the gentamycin antibiotic was associated with calcium carbonate (aragonite 55% with gentamycin) to deliver this active substance on the surgical site for local treatment. The tricalcium phosphate biomaterial was used as the control because of its high biocompatibility. The bony remodelling of these three biomaterials was studied by in vivo experiments. This study was ensured with neutron activation analysis (NAA). The resorption kinetic was elaborated and comparisons of the remodelling biomaterials CaCO(3) 55% and CaCO(3) 55% with gentamicin (vectabone) and tricalcium phosphate were carried out. The obtained results show that, 6 months after implantation, the mineral composition of vectabone and tricalcium phosphate becomes close to that of young bone. Twelve months after implantation, it becomes similar to that of mature bone.

Comparative Study of Nanobioactive Glass Quaternary System 46S6

Different bioactive glass systems have been prepared by sol-gel. However, the production of Na2O-containing bioactive glasses by sol–gel methods has proved to be difficult as the sodium nitrate used in the preparation could be lost from the glass structure during filtration and washing. The aim of this study was to prepare the quaternary system 46S6 of bioactive glass by modified sol-gel techniques with a decrease in the time of gelation. In addition, compare the behaviour of the prepared sol-gel bioactive glass system by its corresponding prepared by melting. The obtained glasses were characterized by using several physicochemical techniques; XRD, FTIR, TEM and SEM beside the effect of the glass particles on the viability of osteoblast like cells (Saos-2). Results show that nanopowders 40-60 nm of 46S6 glass system had been prepared by modified sol-gel (acid-base reaction) method at 600°C in just three days at 600°C. Cell viability by MTT assay confirmed the effectiveness of the prepared nanobioactive glass.