Preparation and characterization of polysaccharide hydrogel systems with gradient structure

This bachelor thesis deals with the preparation of polysaccharide hydrogels with a diffusion gradient and their subsequent characterization in terms of viscoelastic properties, which are used to demonstrate the gradient structure. The main goal was to select a suitable method for the preparation of chitosan hydrogels with different molecular weights (168 kDa - 437 kDa). The biopolymer chitosan is a cationic polysaccharide that is suitable for use in biomedical applications due to its excellent biocompatible properties. First, concentration-uniform hydrogels without gradient structure were prepared, in which the influence of various parameters (chitosan molecular weight, chitosan concentration, sodium hydroxide concentration) was investigated. To prove the created gradient structure, the samples were subjected to the drying method (determination of the dispersion fraction) and determination of mechanical properties by oscillatory rheometry. Increased attention was paid to the search for a suitable preparation method for gradient chitosan hydrogels with higher molecular weight, which showed some problems with the already established method of preparation of hydrogels with gradient structure controlled by diffusion. From the results of the measurements obtained, it can be concluded that the viscoelastic properties of the hydrogels can be modified by changing the selected parameters and the method of preparation. By the controlled diffusion method, it was possible to prepare hydrogels with a gradual gradient of cross-linking density, which confirmed the assumption that the more cross-linked the layer, the higher the values of viscoelastic moduls and therefore the higher resistance to stress was confirmed