A. Rámila

Mesoporous MCM-41 as Drug Host System

Among the large number of applications of mesoporous MCM-41 materials, we have recently developed their new use as drug delivery system. Since this kind of materials consist on a disordered network of siloxane bridges and free silanol groups, these latter could be the reacting sites against appropriate guest chemical species.In this work, this application of mesoporous MCM-41 as drug delivery system has been studied from the host-guest interaction point of view. Two factors could affect that interaction: the structure of pore wall surface, and the functional groups present in the organic molecule. Hence, two approaches have been performed: functionalising pore wall groups and changing the drug.

Static and dynamic in vitro study of a sol-gel glass bioactivity.

A comparative study of in vitro bioactivity of a sol-gel glass with composition 55% SiO2-41%CaO-4%P2O5 has been carried out by soaking it in a simulated body fluid (SBF) with and without exchange of this solution. When SBF is kept constant (static assay) the solution composition changes, increasing the Ca2+ concentration and pH as a function of soaking time while these parameters remain nearly constant and very close to human conditions in dynamic conditions. Glass surface is studied by FTIR, XRD and SEM in order to compare the behaviour in the two procedures, revealing that in both cases an apatite-like layer is formed on the glass surface, although there are differences in rate and morphology in this formation. In addition, a study of porosity was carried out by Hg intrusion pointing out the pore distribution and changes in porosity with time for both procedures. A similar behaviour in mesopore region was detected, while macropores remain nearly constant in static conditions, decreasing from 0.48 to 0.12 microm in just 3 h of soaking in dynamic assay.

Drug release and in vitro assays of bioactive polymer/glass mixtures

The bioactive behaviour and drug release of samples composed by sol gel glass with composition 80SiO2-16CaO2-4P2O5% mol, polymethylmethacrylate (PMMA) and gentamicine or ibuprofen have been studied. The bioactive behaviour of the samples does not depend on the amount (5% and 10% in weight) or on the type of drug used in this study. In all the cases the SEM micrographs show the formation of a layer that covers the surface of the samples after 24 hours soaked in simulated body fluid (SBF). X ray diffraction patterns show two broad peaks after being soaked 3 days. These peaks could be identified with an apatite-like phase, characteristic in this kind of studies.On the contrary, the release kinetics is strongly dependent on the drug employed. In the case of gentamicine, the curve shows a high slope during the first day soaked in SBF and the complete release occurs before 150 hours. For the ibuprofen samples, the drug release is much slower; the samples containing 10% of ibuprofen do not reach the total release after 600 hours. This different behaviour could be related with the solubility of both drugs in aqueous media.