Chitosan and Silica Bioactive Glass 3D Porous Composite for Tissue Engineering
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Kudosteknologinen kitosaanin ja bioaktiivisen lasin huokoinen 3D-komposiitti
The aim of the study was to fabricate and characterize three-dimensional (3D) chitosan and bioactive glass composite scaffolds. Chitosan, as a natural polymer has suitable properties for tissue engineering applications, and combining it with bioactive glass, known to promote bone regeneration, evoked promising results. Chitosan-Bioactive glass composites were made by dissolving chitosan in acetic acid, and adding the bioactive glass to the solution until reaching uniform content. Three glass contents were tested in this project. The porous 3D composite scaffolds were made using freeze drying method. Sodium hydroxide (NaOH) was used as neutralizing agent to remove the acidity from the scaffold. The actual glass content, within the scaffolds, was evaluated by thermogravimetry analysis, and change in the sample porosity and mechanical properties evaluated as a function of glass content. Scaffolds were immersed in TRIS buffer solution for ten different time points (from 6 hours to 5 weeks). After immersion, the sample mass loss and water uptake was quantified. The solution was analysed based on changes in pH and Ca2+ concentration. The mechanical properties of the wet samples were tested to mimic more accurately the in-vivo conditions. Chitosan has a spongy structure with cylindrical pores. The porosity was found to decrease with increasing the glass content. Compressive strength was measured at 50% strain and was found to increase with the glass content. However, both the compressive strength and the elastic modulus showed a maximum at 29 wt% of glass introduced in the chitosan matrix. Immersion in TRIS buffer solution clearly led to degradation of the composite. With adding the glass particles, a rise in pH was noticed, attributed to the leaching of ions from the glass to the surrounding. This was further confirmed with the increasing calcium concentration within the immersion medium. For prolonged immersion time infrared spectroscopy seemed to indicate precipitation of a hydroxyapatite layer, which was not evenly distributed at the surface of the composites. Wet mechanical testing was found to lead to lower elastic modulus and compressive strength than when tested dry. However, the heavy swelling of the samples was also found to lead to high inaccuracy in the measurements.