Lizette Morejón Alonso

Hydrothermal Method for Preparing Calcium Phosphate Monoliths

A new hydrothermal route for preparing biphasic calcium phosphate monoliths is proposed. Firstly, a slurry of b-tricalcium phosphate/ortho-phosphoric acid (b-TCP/H3PO4) is cast into the desired final shape and size to obtain a block composed of dicalcium phosphate dihydrate (DCPD) and b-TCP. This block is then treated in 1.0 M Na2HPO4 at 60 °C in order to hydrolyze the DCPD into Ca10-x(HPO4)x(PO4) 6-x(OH)2-x (CDHA) and Ca8H2(PO4)6 .5H2O (OCP). The result is a monolithic piece which preserves the initial shape and size, but which is composed instead of CDHA, OCP, and b-TCP. During the initial stage, when the pH is slightly alkaline, the product of DCPD hydrolysis is CDHA. However, when a neutral or slightly acidic pH is reached OCP is formed. Test samples processed by this method showed complete conversion of DCPD into CDHA and OCP after 112 h of hydrolysis, and with a compressive strength of 16.2 MPa, similar to cancellous bone.

Calcium phosphate glasses: Silanation process and effect on the bioactivity behavior of glass-PMMA composites

This article presents the results of a study of the efficiency of silanation process of calcium phosphate glasses particles and its effect on the bioactivity behavior of glass- poly(methyl methacrylate) (PMMA) composites. Two different calcium phosphate glasses: 44.5CaO-44.5P2 O5 -11Na2 O (BV11) and 44.5CaO-44.5P2 O5 -6Na2 O-5TiO2 (G5) were synthesized and treated with silane coupling agent. The glasses obtained were characterized by Microprobe and BET while the efficiency of silanation process was determined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Thermal Analysis (DTA and TG) techniques. The content of coupling agent chemically tightly bond to the silanated glasses ascended to 1.69 ± 0.02 wt % for BV11sil glass and 0.93 ± 0.01 wt % for G5sil glass. The in vitro bioactivity test carried out in Simulated Body Fluid (SBF) revealed certain bioactive performance with the use of both silanated glasses in a 30% (by weight) as filler of the PMMA composites because of a superficial deposition of an apatite-like layer with low content of CO3 (2-) and HPO4 (2-) in its structure after soaking for 30 days occurred.

Hydroxyapatite Nanoparticles: Synthesis by Sonochemical Method and Assessment of Processing Parameters via Experimental Design

Hydroxyapatite (HAp) has been synthesized by different techniques, and sonochemical methods have shown to be useful in the HAp nanopartcicles production for biomedical applications such as bone graft substitute. In addition, experimental design is an appropriate tool for planning and evaluating a study to meet specified objectives. Then, this work aimed to synthesize HAp nanosized powders by a sonochemical method and assess the processing parameters via experimental design, in order to obtain dense samples. HAp nanopowders were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope/Field Emission Gun (SEM/FEG). For densification analysis, HAp samples were processed with different parameters, such as: compaction pressure (200 or 400 MPa), sintering temperature (900 or 1100°C), sintering heating rate (2 or 20 °C/min), and sintering time (2 or 4 hours). The samples were analyzed by SEM/FEG, whereas the linear shrinkage and density were considered the response variables for the experimental design. The results indicated that the sonochemical method successfully produced HAp nanoparticles with sphere-like morphology. Further, the experimental design showed that sintering temperature was the variable that most influenced the densification of samples.

Evaluation of acrylic bone cements with single and combined antibiotics: Release behavior and in vitro antibacterial effectiveness

ABSTRACTThis work studied the eluting behavior of Ciprofloxacin, Meropenem and Ceftazidime (and their mixtures) with that of Gentamicin from antibiotic loaded bone cements (ALBCs). In vitro release was followed by UV-Vis for 30 days and a semi-empirical eluting model that considers the processes of dissolution and diffusion was proposed: . The antimicrobial efficacy against P. aeruginosa and S. aureus of the prepared ALBCs was also evaluated. The results showed that the amount of antibiotic released increased when Ciprofloxacin/Meropenem or Ciprofloxacin/Ceftazidime were used and that their antibacterial inhibitory effect against microorganisms tested was improved as a consequence of the synergistic effect.ABSTRACT This work studied the eluting behavior of ciprofloxacin, meropenem, and ceftazidime (and their mixtures) with that of gentamicin from antibiotic-loaded bone cements (ALBCs). In vitro release was followed by UV–Vis for 30 days and a semiempirical eluting model that considers the processes of dissolution and diffusion were proposed: . The antimicrobial efficacy against Pseudomonas aeruginosa and Staphylococcus aureus of the prepared ALBCs was also evaluated. The results showed that the amount of antibiotic released increased when ciprofloxacin/meropenem or ciprofloxacin/ceftazidime was used and that their antibacterial inhibitory effect against microorganisms tested was improved as a consequence of the synergistic effect. GRAPHICAL ABSTRACT

Study on Processing and Characterization of Calcium Phosphate Bioceramics

The calcium phosphate bioceramics are widely used for the bone reconstruction because of their mineralogical similarities. This work aimed to obtain a biphasic calcium phosphate from hydroxyapatite nanoparticles synthesized by sonochemical technique and processed under two different conditions. The samples were uniaxially cold-pressed at 200MPa and sintered at 900°C/2h (CP900) and 1000°C/2h (CP1000) with heating rates of 2°C/min and 5°C/min, respectively. The characterizations were performed by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and theoretical elastic modulus. From the geometric method, the relative density, porosity and linear shrinkage were measured. The results showed that the studied processing conditions were useful for achieving samples formed by a biphasic calcium phosphate with 80% β-tricalcium phosphate and 20% hydroxyapatite. The CP900 and CP1000 samples presented a theoretical elastic modulus of 34.7 GPa and 53.1 GPa, respectively, which are higher than that found to the compact bone. In addition, the sintering at 900oC was sufficient to promote neck formation and particle coalescence, maintaining adequate porosity (47.5%) for bone tissue ingrowth into pores.

Different Synthesis Routes for Hydroxyapatite Nanoparticles by Mechanical Stirring

Nanosized hydroxyapatite (HA) with crystallinity and composition similar to bone apatite has been widely investigated in the last years, due to their excellent biocompatibility in bone replacement applications. This bioceramic can be synthesized by many wet chemical and mechanochemical methods. In this paper, nanosized hydroxyapatite powders were synthesized by two wet chemical routes using mechanical stirring method. The first route was used for HA synthesis from CaCl2.2H2O and Na3PO4.12H2O solutions and the second route was from Ca (OH)2 and H3PO4 solutions. The synthesized HA nanoparticles were characterized by Dynamic Light Scattering, BET Surface Area analysis, X-ray Diffraction, Infrared Spectroscopy, chemical analysis and Scanning Electron Microscopy. The results indicated that HA nanoparticles were successfully synthesized by both wet chemical precipitation routes and all powders presented a Ca/P ratio similar to stoichiometric HA, nanoneedles morphology and single HA crystalline phase.

Effect of Sonochemical Technique on the Morphology and Crystallinity of Hydroxyapatite Nanoparticles

Hydroxyapatite (HA) is the main mineral component of bones and teeth, and for this reason its synthetic analogous has been used with excellent clinical results as bone substitute. The biological apatite is typified as a poorly crystalline carbonate apatite (CHA) formed by nanosized particles with a great superficial area. This work aimed to study the influence of ultrasound technique on the morphology and crystallinity of nanoHA synthesized by chemical precipitation method. The nanoHA particles were obtained from CaCl2·2H2O and Na3PO4·12H2O raw solutions and a powerful ultrasonic sound (UP400S) was used at different conditions during the synthesis. X-ray Diffraction, Infrared spectroscopy, Chemical Analysis and Scanning Electron Microscopy were used to characterize the synthesized nanoHA particles. The results indicated that HA nanoparticles with nanorods morphology were obtained in all conditions. By Scherrer`s formula, the crystallite size was determined and it was found that the increasing in ultrasound amplitude enhances the nanoparticles crystallinity.

Sintering Behavior of Nanostructured Hydroxyapatite Ceramics

The synthesis of nanoparticles appropriate for the preparation of nanostructured hydroxyapatite ceramics intended for bone repairs and regeneration is an interesting field of biomaterials research today. In this work nanoparticles of hydroxyapatite were obtained by the precipitation method using conventional magnetic stirring (A) and ultra turrex homogenizer (T1) accompanied with surfactant (T2) and dispersant agents (T3). In all cases, powders with nanometric dimensions were obtained and the unique calcium phosphate phase detected was hydroxyapatite (HAp). The powders sintering behaviour was studied. The ceramics obtained from powders prepared by magnetic stirring (A) showed the best values of final density (96.7 %) which it was in agreement with the lowest temperature of the beginning of shrinking (648.6 °C) during sintering determined by dilatometry. Nanostructured nature of these ceramics was confirmed by Scanning Electron Microscopy (SEM).

Obtaining new formulations of inclusion resin for optical microscopy. Introduction of its use in animal tissue

Using different plasticizers, we have obtained two formulations for inclusion synthetic material. Both formulations were evaluated following two criteria: Shore D tests of hardness reported for this kind of compounds, and histopathological studies in animal tissue. Through these tests of hardness we have confirmed that both materials have the adequate properties to be used as means of inclusion. These produced results very similar to those reported previously. From the histopathological studies performed, we were able to confirm the effectiveness of the proposed formulations. Comparatively, we also selected the use of di-ethylhexyl phthalate as a very effective plasticizer, obtaining clearer results of the details of the tissue, as well as being easier and faster to use, among other advantages.ResumenSe obtuvieron dos formulaciones para material sintético de inclusión, empleando plastificantes diferentes. Ambas formulaciones fueron evaluadas siguiendo dos criterios, ensayos de dureza de Shore D documentados para este tipo de compuestos, y estudios histopatológicos en tejido animal. Mediante los ensayos de dureza se comprobó que ambos materiales presentan las propiedades adecuadas para ser utilizados como medios de inclusión, arrojando resultados muy similares a los informados con anterioridad. De los estudios histopatológicos realizados se pudo comprobar, en primer lugar la eficacia de las formulaciones propuestas, y comparativamente pudimos seleccionar el empleo del ftalato de bis (etilhexilo) como plastificante muy ventajoso, obteniéndose resultados mucho más nitidos de los detalles del tejido, así como resultando un medio más fácil y rápido de emplear, entre otras ventajas.