M.V. Cabañas

Tailoring vancomycin release from β-TCP/agarose scaffolds

In this work a multifaceted approach to the fabrication of scaffolds is considered, that is, besides the preparation technique, the introduction of substances that may contribute to enhance their final performance, as well as the techniques required to ensure the correct preservation of the so obtained scaffolds are taken into account to tailor the release of vancomycin from beta-tricalcium phosphate (beta-TCP)/agarose scaffolds. These materials were prepared by a shaping technique that allows to obtain pieces at a temperature low enough to simultaneously include active substances susceptible of heat degrading such as vancomycin, the model drug considered in this work. In the first approximation poly(ethylene glycol) (PEG), a hydrophilic substance employed as a matrix capable of binding compounds such as proteins or peptides and release them in a controlled fashion, was included in the formulation. The second tool to govern the vancomycin liberation is based on the drying procedures employed to process and preserve the obtained scaffolds: freeze-drying and heat desiccation at 37 degrees C. These modifications resulted in the generation of different pore architectures and certain chemical interactions, such as the formation of an agarose-PEG-vancomycin complex that yielded different drug release patterns. The so obtained pieces behave like a hydrogel when immersed in a hydrated medium but show a consistency comparable to that of the cancellous bone.

Evolution of the microstructure and its influence on the magnetic properties of aerosol synthesized BaFe12O19 particles

Hexagonal ferrites of which the prototype is BaFe[sub 12]O[sub 19] are well known not only as permanent magnets, but also as emerging magnetic recording media and as potential magneto-optical devices. The magnetic properties are strongly dependent on preparation method. So considerable efforts have been devoted to preparing pure and doped BaFe[sub 12]O[sub 19] fine particles, smaller than 1 [mu]m, to be used as magnetic recording media. Small BaFe[sub 12]O[sub 19] particles have been synthesized from an aqueous solution of barium and iron nitrates by an aerosol synthesis technique. Starting hollow spherical particles were annealed under several conditions. Hexagonal-like platelets were obtained at the final stage of a sintering process which has been followed by X-ray diffraction and scanning electron microscopy. The influence of the microstructure evolution on the magnetic properties is discussed.

Spherical iron oxide particles synthesized by an aerosol technique

Spherical particles of several iron oxides have been obtained by pyrolysis of an aerosol generated by ultrahigh frequency spraying of a solution. Two different precursor solutions were used to produce the aerosol: Fe(NO 3 ) 3 · 9H 2 O and FeC 6 H 5 O 7 · 4H 2 O. The iron nitrate decomposition leads to the formation of α-Fe 2 O 3 , while the organic precursor pyrolysis leads to magnetic particles of either γ–Fe 2 O 3 or Fe 3 O 4 . Structural phase, particle size, texture, and homogeneity of the products so obtained can be controlled as a function of some synthesis conditions such as precursor solution, temperature, solution concentration, and surrounding atmosphere.

LaAlO3 thin film deposited on Si(100) and MgO(100) substrates

Abstract LaAlO3 films have been deposited on Si(100) and MgO(100) substrates by a modified CVD process. Solutions of aluminum and lanthanum acetylacetonates were used as precursors. The influence of both deposition temperatures and substrates on the characteristics of these thin films has been studied.

Thin films of magnesium oxide by modified CVD : a buffer layer for HTCS films

Abstract Magnesium oxide thin films, as buffer layers for depositing high-T c superconducting thin films, were prepared by a modified CVD process. This process uses pyrolysis of an aerosol produced by ultra-high frequency spraying of a solution. The raw material was magnesium acetate dissolved in ethanol or butanol. The deposition was carried out in air between 450 and 600°C and thickness varies between 100 and 500nm. A highly 〈100〉 oriented polycrystalline film can be obtained on oxydized silicon wafers. The influence of deposition parameters on the film growth was examined by X-ray, SEM. Grain size varies between 60 and 150 nm. Electrical properties were examined by complex impedance spectroscopy and I(V) characteristic: resistivity (>10 12 Ω.cm) and dielectric constant.

Calcium phosphate coatings deposited by aerosol chemical vapour deposition

Thin films of calcium phosphates with different crystallinity and Ca/P ratios have been prepared by the pyrosol method and characterised by XRD, FTIR, EDS and SEM. The microstructure, crystallinity and composition of the deposited films can be controlled by modifying the composition of the precursor solution, reactor atmosphere and substrate temperature. Using this method, pure hydroxyapatite with varying crystallinity and microstructure can be obtained under more oxidising conditions, whereas tricalcium phosphate (α or β) or biphasic hydroxyapatite–tricalcium phosphate mixtures can be obtained under argon atmosphere. The ability to vary the calcium phosphate phases deposited has significant implications for the use of these films in implant devices.

Influence of the synthetic route on the BaFe12O19 properties

Abstract BaFe 12 O 19 has been synthesized by four different procedures: Ceramic method, nitrate decomposition, liquid mix technique and pyrosol method to study the influence of the synthetic route on the textural and magnetic properties. Smaller particles are obtained by both the liquid mix technique and the pyrosol method leading to samples with higher coercive field.

Influence of synthesis conditions on the γ-Fe2O3 properties

Abstract Hydrolysis and pyrosol methods have been used to synthesize β- and γ-FeOOH. Different temperatures were used in order to transform these precursors to γ-Fe 2 O 3 and therefore different size distribution and surface/volume ratio were observed. Consequently, distinct magnetic behaviour (superparamagnetic or ferrimagnetic) in γ-Fe 2 O 3 depending on the precursor obtention method was observed.

Apatite Layers by a Sol-Gel Route

Abstract. Carbonate-hydroxyapatite coatings were deposited by a sol-gel method using sols with different characteristics, i.e. with different ethanol content. In calcium phosphate film preparation, an important factor in determining the composition of the layers is the aging time of the sol, which in turn depends on the precursor-sol characteristics. The shortest tim to synthesize hydroxyapatite was observed when an aqueous system was used, but the sols containing e hanol are stable for a longer time, and more homogeneous coatings are obtained.