Bioactive organic-inorganic hybrid aerogels
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Bioactive organic-inorganic hybrid aerogels Luis Esquivias, Víctor Morales-Flórez, Manuel Piñero1, Nicolás de la Rosa-Fox, Julio Ramírez2 José González-Calbet2, Antonio Salinas3 and María Vallet-Regí3 Departamento de Física de la Materia Condensada, Facultad de Ciencias, UCA. Puerto Real 11510 Cádiz, Spain. 1 Departamento de Física Aplicada, CASEM, UCA 2 Departamento de Química Inorgánica. Facultad de Químicas. UCM. 3 Departamento de Química Inorgánica y Bioinorgánica. Facultad de Farmacia. UCM ABSTRACT We have prepared organic-inorganic hybrid materials (OIHM), incorporating an organic phase in the inorganic precursor sol, using high power ultrasound for assistance with agitation. A sono-ormosil results after gelation. Colloidal silica particles have been added to these hybrids to enable network porous volume and pore radius to be tailored to specific requirements. Finally, in vitro bioactivity of this material has been promoted by adding calcium to the initial sol. The structure and bioactivity of these materials have been subjected to preliminary study, including their mechanical behaviour. These materials have a very fine structure especially after colloidal silica particles have been included. When immersed in a solution simulating blood plasma, they are bioactive, and the sample with colloid particles presents a better behaviour in vitro INTRODUCTION Organic-inorganic hybrid materials (OIHM) are being used for implants since they are tolerated by the human organism, which creates a fibrous tissue that surrounds them when they are embedded in the body. However, they do not become bonded to the bone unless they are bioactive. When they have this characteristic, a layer of hydroxycarbonateapatite (HCA) grows and envelops the material when it is immersed in blood plasma. An HCA layer is also formed when bioactive materials are soaked in solutions mimicking the properties of plasma. In general terms, these materials are categorized as bioactive. The biologically active HCA layer facilitates the interaction of material and biological entities, and this is proposed as a first phase in the sequence of reactions that results in the creation of a mechanically strong bond between the bioactive materials and the living tissues [1]. For them to perform fully as bone implants, these materials need to present mechanical behavior approaching that of human bones. Recently, several types of mixture obtained by ultrasonic agitation of colloidal silica with a sol solution containing tetraethoxysilane (TEOS) were used to form crack-free monoliths. The addition of colloid silica particles to TEOS-based alcogels has enabled the parameters of network porous volume and pore radius to be tailored as required. We have used this colloid-polymer combination as the precursor of the inorganic part of the OIHM, with the aim of tailoring the porosity to give it the density and mechanical strength in the ranges typical of human bones. Finally, in vitro bioactivity of this material has been promoted by adding calcium to the initial so
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