چكيده به لاتين
The purpose of this project is to prepare bioactive glass-chitosan composite to investigate the effect of the presence of magnesium and strontium oxides in the composition of glass on the biological properties, injectability, viscosity and bioactivity of the mentioned system. For this purpose, the glass system of 64SiO2. 31CaO. 5P 2O 5 was synthesis by acid-base sol-gel method. Then, by replacing 4% mol SrO and 4% mol MgO with CaO in the previous glass system, two separate glass systems were synthesized in the same way. Finally, by simultaneously replacing 4% MgO and 4% SrO with CaO in the initial glass system, another glass was synthesized to compare the properties in presence of these two oxides. Then the prepared powders were characterized by X-ray diffraction, SEM and FTIR. In examining the phase of the synthesized glasses, no peak was observed in the X-ray diffraction pattern of the glasses after calcination at 750℃ for 5 hours. Also, in the morphological analysis, the glass particles are agglomerated and the average particle size in them is reported in the following: BG (85±0/022 nm), BGM (104±0/029 nm), BGS (64±0/018 nm) and (84± 0/024 nm). In the preparation of composite pastes, at first 3% chitosan solution was prepared and to select the optimal P/L ratio, the chitosan solution was mixed with different proportions of bioglass powder and tested for mechanical properties. Therefore, the ratio of 0/25 was confirmed as the optimal ratio for the percentage of powder to liquid. the injectability of pastes was evaluated under controlled conditions with a constant force and speed of 30 mm/min. by adding magnesium ions in the composition, the injection force in a syringe with a diameter of 2mm increased from 2/17∓1 newtons to 2/50±2 newtons and by adding strontium to The combination, the injection force reached 5/10±1 newtons, also in the simultaneous presence of magnesium and strontium, the injection force increased up to 6/83± 0/8 newtons. In the rheometric studies of the pastes, in the viscosity/shear rate curve, by increasing of the shear rate, the viscosity decreased and the pastes showed shear thinning behavior. Also, by adding magnesium to the glass composition, the viscosity increased from 402 pa.s to 2320 pa.s, and with the presence of strontium, the viscosity increased to 3490 pa.s. Also, in the simultaneous presence of magnesium and strontium, the viscosity increased up to 3770 pa.s. On the other hand, in the shear stress/shear rate curve, with the increase of the shear stress up to 1410 pa, the shear rate increased. Therefore in a constant shear stress, viscosity of BGM/BGS/BGMS was higher than the viscosity of BG.
In the study of bioactivity, after 14 days of immersion of the pastes in SBF solution, a layer of hydroxyapatite and calcite was formed on the surface, which represents the biocompatibility of the pastes. BGS showed higher degradation in SBF solution than other pastes and its chemical resistance decreased from 91/23 to 82/49. However, due to the more severe pH changes in BGS paste and its higher reactivity in the body simulator environment, apatite crystals formed more in the presence of strontium-containing paste. Also, in the presence of magnesium ions, the chemical resistance increased up to 96/38 due to the increase of network cohesion. Therefore, the formation of calcite was not observed in the paste containing magnesium, but in other composites, due to the open network compared to the paste containing magnesium, calcite was formed on the surface and dissolved and turned into hydroxyapatite in 14 days. In the biological investigation, the compatibility behavior of the pastes with the MG63 cell line was also investigated for 1 and 3 days, and the results showed that the synthesized pastes in percentages less than 100% did not show any destructive effect on osteoblast cells. Finally, it can be claimed that the prepared composites can be a good candidate for replacement with restorative materials in bone tissue regeneration.
