Síntesis y caracterización de materiales híbridos base APS para su potencial aplicación como sustituto de tejido óseo

Abstract

Resumen En el presente trabajo se desarrollaron materiales híbridos de los sistemas APS-PDMS y APS-PDMS-TEOS modificados con Ca. Se determinaron las características microestructurales de los híbridos sintetizados y se llevó a cabo la evaluación de su bioactividad y degradabilidad hidrolítica para determinar su potencial uso como regenerador de tejido óseo. Los materiales se prepararon mediante el procesamiento sol-gel utilizando como precursor orgánico el polidimetilsiloxano (PDMS) y como precursor inorgánico el aminopropiltrietoxi silano (APS) y el tetraetil ortosilicato (TEOS). Las reacciones de hidrólisis condensación se llevaron a cabo en medio ácido (HCl) para los sistemas que contienen TOES y se utilizó como solvente común al isopopanol. Con la finalidad de proporcionar características bioactivas, se adicionó una sal de calcio (CaNO3. 4H2O). Los materiales se caracterizaron mediante las técnicas de DR-X, MEB, FT-IR. La degradabilidad se evaluó mediante la pérdida de peso y cambios de pH después de que los materiales fueron inmersos en diferentes periodos de tiempo (1, 3, 7, 14, 21 y 28 días) en una solución buffer de fosfatos (PBS) así como los cambios en la morfología de los materiales en los tiempos descritos. La bioactividad fue evaluada por la presencia de una capa de apatita sobre la superficie de los materiales. Los resultados mostraron la influencia del contenido de APS en las propiedades y características de los materiales híbridos sintetizados, así como su capacidad bioactiva y de degradación. Abstract In this work hybrid materials of the APS-PDMS and APS-PDMS-TEOS systems were developed with Ca. The microstructural characteristics of the synthesized hybrids were carried out to determine their potential use as a regenerator of bone tissue. The materials were prepared by sol-gel processing using polydimethylsiloxane (PDMS) as the organic precursor and aminopropylethoxy silane (APS) and tetraethyl orthosilicate (TEOS) as an inorganic precursor. The condensation hydrolysis reactions were carried out in acid medium (HCl) for systems containing TOS and used as the common solvent for isopropanol. In order to provide bioactive characteristics, a calcium salt (CaNO3.4H2O) was added. The materials were characterized by the techniques of DR-X, MEB, FT-IR. The degradability was evaluated by weight loss and pH changes after the materials were immersed in different phosphate buffer solutions (SBF) at different time periods (1, 3, 7, 14, 21 and 28 days) as well as changes in the morphology of materials at the times described. The bioactivity was evaluated by the presence of an apatite layer on the surface of the materials. The results showed the influence of the APS content on the properties and characteristics of the synthesized hybrid materials, as well as their bioactive and degradation capacity.

Abstract The aim of this work was to develop organic-inorganic hybrid materials based on silica and titanium by sol-gel process, using a biocompatible, bioactive and biodegradable organic component with potential application as bone substitute. This was carried out in two stages. In the first stage a series of polyesters were prepared using the polymerization stages by fusion technique, using polyethylene glycol of different molecular weight and citric acid as precursors. The second stage corresponds to the synthesis of hybrid materials through the sol-gel technique. Hybrid materials were synthesized with two organic / inorganic compositions, using as organic component polyesters synthesized in the step one and as inorganic component, metal alkoxides as precursors of titanium and silica, subsequently the effect of the hybrid composition in the degradability, biocompatibility and bioactivity of the materials was studied. The material characterization was performed using Spectroscopy Fourier Transform Infrared (FT-IR), Raman spectroscopy (Raman), X-ray diffraction (XRD), scanning electron microscopy (SEM) Permeation Chromatography gels (GPC), Helium pycnometry for real density, bulk density by the Archimedes method, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) techniques and cell biocompatibility. In vitro degradability properties were evaluated evaluated in phosphate buffer solution (PBS), bioactivity in simulated body fluid and biocompatibility with biological tests by osteoblast cells. Measurements of pH, weight changes and characterization techniques above were performed. Hybrid materials with thermal stability up to 180 °C were obtained. Moreover, the materials have microstructures and textures dependet on the polyester molecular weight used; hybrid materials with polyester precursor of higher molecular weight are highly dense and hybrid materials with lower molecular weights are porous. The results of bioactivity tests show that the organic component has a large influence due to the formation of acid groups in aqueous solution which decrease the pH of the simulated body fluid solution, inhibiting the formation of hydroxyapatite. In the other hand, it was observed that the selected materials have values of cell viability above 75% which make them viable for application as substitutes for bone tissue. In order to increase the degree of crosslinking of the hybrid materials to increase the structural stability, reduce its acidity in solution and observed the variation in chemical and physical properties, heat treatments were performed with 6 out of the 9 synthesized hybrid materials. This changes are explained due to rearrangement of the polymer chains of the polyester in the hybrid materials organic phase. Additionally by FT-IR it was observed an increase in the intensity of the carbonyl bond (C=O) at 1730 cm^-1 and growth of the band at 1192 cm^-1 which is characteristic of the O-CO link in ester group. These variations are due to increased ester polymer chains after heat treatment.