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Crosslinking of polysaccharide microfibers
Svidroňová, Barbora ; Abdellatif, Abdelmohsan (oponent) ; Vojtová, Lucy (vedoucí práce)
The general goal of the proposed diploma work was preparation and characterization of crosslinked hyaluronan microfibres, which would be stable in aqueous environment with proper mechanical properties. The fibres prepared by the wet spinning technique, were crosslinked with solution containing crosslinking reagent 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide or two crosslinking reagents, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide, leading to amidation and formation of ester bonds. Characterization of prepared samples is the main goal of experimental part of the thesis. The swelling characteristics were carried out to determine the stability of fibres in three different solutions (with pH 7.4, 3 and 11). For determination of thermal stability was used thermogravimetrical analysis, and for determination of esterification and amidation was used infrared spectroscopy with Fourier transformation. Mechanical properties of fibres were studied by stress-strain tester. Additionally, the rheological properties were investigated, as well as the microstructure and surface of fibres by scanning electron microscopy. The fibres before chemical crosslinking had lower stability in all three types of solutions; the thermal stability was also lower, than the stability of crosslinked fibres. For not chemically modified fibres with crosslinking reagent, only one type of peak for esterification occurred. The infrared spectra of chemically crosslinked fibres showed the presence of two esterification peaks, which was the result of the effectiveness of the crosslinkig reagent. Amidation was also stronger for crosslinked fibres, especially for fibres crosslinked long time and in the solution with higher concentration of crosslinking reagent. Due to the heterogeneity of fibres, mechanical properties did not show evidence of any dependence on the crosslinking. The rheological study showed that the viscosity of fibre dissolved in water is less dependent on the shear rate than the powder of sodium hyaluronan dissolved in water. Despite more different methods of characterization of fibres which were used in this work, there are still many options for better characterization and closer understanding of this biopolymeric material.
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