Papers by Author: Gisela M. Luz

Abstract: In this study a new P-free system applied to the production of Bioactive Glass Nanoparticles (BG-NPs) is proposed, in order to evaluate the effect of suppressing this component, in the bioactivity capability of the materials. The BG-NPs, based on both ternary (SiO2-CaO-P2O5) and binary (SiO2-CaO) systems, were prepared via a sol-gel method. The morphology and composition of the BG-NPs were studied using FTIR and SEM. New composite membranes were produced combining chitosan and the BG-NPs. The bioactive character of the prepared biodegradable membranes was accessed in vitro by analyzing the capability for apatite formation onto the surface after being immersed in simulated body fluid (SBF). EDX and SEM were used to confirm the bioactivity of the materials.

Abstract: A number of combinations of biodegradable polymers and bioactive ceramics have been used for orthopaedic applications including in hard tissue regeneration. Ideally, composites aimed to be used in orthopaedic applications should combine adequate mechanical properties and bioactivity. Chitosan (CTS) has been widely used for biomedical applications, namely in tissue regeneration or drug delivery. In this sense, membranes of chitosan and chitosan with Bioglass® (BG) were prepared by solvent casting and characterised using Scanning Electron Microscopy. In vitro bioactivity tests were performed in the composite membranes, namely by monitoring their capability to induce the precipitation of apatite upon immersion in simulated body fluid (SBF). The results showed that the addition of BG promoted the deposition of an apatite-like layer. The deposition of apatite could influence the mechanical performance of the material. Therefore, in order to follow this biomineralization, the viscoelastic properties of these composite membranes (immersed in SBF) were evaluated. The change in the storage modulus (E’) and the loss factor (Tan δ) were measured as a function of immersion time using non-conventional dynamic mechanical analysis (DMA) tests, in which the samples were kept in wet conditions and at 37°C during the measurements. The mechanical properties of the chitosan membranes were improved by the addition of BG particles. An increase on the storage modulus was observed by the composite membranes while for the pure chitosan membranes the storage modulus was stable up to 7 days. Clear changes were detected in the composite membranes that contrasted with pure chitosan (CTS) membranes that exhibit stable viscoelastic properties up to 7 days. In addition, this work showed that sample characterization in the hydrated state can be useful to predict the mechanical performance of composites under meaningful physiological conditions.