Signaling molecules are critically important to regulate cellular processes. Therefore, their incorporation into engineered biomaterials is indispensable for the applications in tissue engineering and regenerative medicine. In particular, the functionalization of highly hydrated polymer networks, so-called hydrogels, with the signaling molecules, has been quite beneficial to provide multiple cell-instructive signals. Following this strategy, the incorporation of sulfated glycosaminoglycans (GAGs) into such polymer networks offers unprecedented options to control the administration of signaling molecules via electrostatic interactions. Moreover, mathematical models can be instrumental in designing materials to tune the transport and adjust the local concentration of the signaling molecules to precisely modulate cell fate decisions. Accordingly, this study aims to systematically investigate the impact of different binary poly(ethylene glycol)-glycosaminoglycan hydrogel networks on the transport of signaling molecules by developing and applying mathematical modeling in combination with experimental approaches. The gained knowledge was then applied to modulate the bioactivities of pro-angiogenic growths factor within the binary hydrogel and rationally design a new class of cytocompatible GAG-based materials for the controlled administration of pro-angiogenic growth factors. Firstly, systematic studies on the mobility of signaling molecules within GAG-based polymer networks revealed differential effects of hydrogel network parameters such as mesh size, GAG content, and the sulfation pattern of the GAG building block on the transport of these signaling molecules. Secondly, the effect of the GAG content of the hydrogel and the sulfation pattern of the GAG building block on the bioactivity of hydrogel administrated vascular endothelial growth factor (VEGF) have been analyzed. Since VEGF is a GAG-affine protein that plays a major role in angiogenesis, its ability to promote vascular morphogenesis has been investigated. The simulation and experimental results demonstrated the determining impact of the availability of free (unbound) VEGF as well as the presence of GAGs with a specific sulfation pattern within the polymer network on the formation of the endothelial capillary network within the hydrogel. Finally, a rational design strategy has been applied to extend a GAG-hydrogel platform to allow for a far-reaching control of its cell instructive properties. The resulting materials are independently tunable over a broad range for their mechanical properties and GAG content. The GAG content of the hydrogel matrices, in particular, was shown to modulate the transport of pro-angiogenic growth factors most. Moreover, the hydrogel also supports endothelial vascular morphogenesis. In conclusion, the in here followed approach of combining experimental results and mathematical modeling for predicting the transport of signaling molecules and the rational design concept for customizing GAG-based hydrogel networks provide the fundamentals to precisely modulate cell fate decisions within GAG-based biohybrid polymer networks rationalizing their application for tissue engineering and regenerative medicine

The scope of this masters thesis is the preparation of a model mucin system and its utilization as an artificial model of the native mucus system. The creation of this model system, according to several designed methods was a part of experimental part of the thesis. The preparation of mucin system comprised of physical and chemical methods of hydrogel formation, screening and characterisation of the various physical conditions of the mucin properties on its molecular level, and the preparation of sorbent with sorption surface containing mucin. Methods of light scattering, namely dynamic light scattering (DLS), used for mucin particles size change monitoring, and electroforetic light scattering (ELS), used for Zeta potential change monitoring, were used for the screening of the impact of physical factors on the properties of mucin.For the characterisation of impact of the temperature on changes in mucin sctructure was, apart from monitoring of light scattering, used also a diferential scanning calorimetry (DSC), which registered temperature value, at which mucin thermal denaturation occurs. In the next part of the thesis we subdued the created sorption surfaces to various physical-chemical analyses, which task is the characterisation and projection of surface and confirmation of mucin presence.Substancial part in monitoring and characterisation of changes in surface sctructure of sorption surface was accomplished by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscophy (SEM) was used for the final, more detailed, projection of the mucin enriched, sorbent surface structure. Suggested methods of mucin hydrogel, didnt prove sufficient results for the possibility of application of hydrogel as a artificial model of real mucus system, but the sorbent application was indicated as a suitable alternative and an instrument for the further mucin behaviour research and possibly subsequent bacterial adhesion, which represents the first step in the formation of the bacterial biofilm.

This Master‘s thesis is focused on the preparation of hydrogels based on a hydrophobic derivative of hyaluronic acid palmitoyl hyaluronan in presence of biosurfactant decyl glucoside’s micelles and micelles of surfactant triton X-100. For followed characterization were chosen rheological tests and infrared spectrometry. There was observed influence of preparation method, type and concentration of surfactant and presence of micelles on final features of the hydrogel. Moreover, an experimental test of swelling was performed with interesting results for future research.

This diploma thesis focuses on the optimization of bacterial cellulose production by Komagateibacter xylinus DSM 46604. The theoretical part of this thesis describes the properties of bacterial cellulose, its production and application possibilities. The experimental part aimed to assess the effect of different cultivation conditions on the production yields of bacterial cellulose. The effects of several cultivation strategies have been studied such as: (1) effect of acetate buffer used as a medium, (2) impact of oil added into the medium, (3) fed-batch cultivation, (4) variation of the volume of cultivation vessel and cultivation media and (5) aeration. In addition to the production of relatively thin samples, up to 100 µm was synthesized unique 3D structured bacterial cellulose in the form of cylinders, with a height up to 2 cm. The growth of bacterial cellulose in the form of cylinders was achieved by dynamically cultivating K. xylinus in combination with fed-batch approach.

No description available.

Pluronics are triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) available in different molecular weights and PPO/PEO ratios. Pluronic hydrogels are able to dissolve hydrophobic compounds and they have application in different areas including drug delivery systems and oil recovery. The structure of Pluronic polymers can be designed for specific application by changing the size and ratio of the PPO and PEO blocks. In aqueous environments, the PPO blocks of different unimers form aggregates as they are more hydrophobic compared to the PEO blocks, and in the aggregates the PPOs have less exposure to water. The PEO blocks that are still hydrophilic remain soluble in water and form a shell around the PPO aggregated core. Moreover, some of the Pluronic copolymer aqueous solutions can form hydrogels at elevated temperatures. The aim of this thesis is to study the microheterogeneity of two different Pluronic hydrogels using singlet excited state probes and also study the mobility of small molecules in Pluronic hydrogels using triplet excited state probes. In the first project, the properties of different microenvironments in Pluronic F127 (PEO99PPO65PEO99) were characterized. The quenching of singlet excited state probes was used to determine the number and characteristics of solubilization sites in F127 hydrogels. This method was used to gain information on the accessibility of different quenchers to singlet excited molecules bound to the micellar structures. Singlet excited states are short lived, and these excited states do not move within the gel before their decay to the ground state. The techniques used for these studies were steady-state fluorescence and time-resolved fluorescence spectroscopies. My results showed that there are different solubilization sites in F127 micelles and the accessibility of quenchers to the singlet excited molecules bound to the micellar structure depends on the nature of the quencher and the size of the excited molecules. In the second project, the different microenvironments in Pluronic P104 (PEO27PPO61PEO27) were characterized, and these results were compared with those obtained for the Pluronic F127. Pluronic P104 has similar units of PPO blocks as F127 but different units of PEO blocks which results in different properties between these two Pluronic copolymers. My results showed that the solubilization sites inside Pluronic micelles changes with the change in PEO/PPO ratio. In the third project, I studied the mobility of different small molecules between aqueous and micellar environments in the F127 hydrogel by quenching triplet excited state probes. Excited triplet states are suitable for such studies because their lifetimes are longer than the lifetimes for singlet excited states. The laser flash photolysis technique was used for this aim. The results showed that the exit from the micellar environment is slow and depend on the size and hydrophobicity of the probe molecules. / Graduate / 2022-05-11

The thesis is focused on physical hyaluronan gels. The object of study is the interaction of hyaluronan (HyA) with oppositely charged surfactants in physiologic solution (0.15 M NaCl), leading to the formation of gel. In the first part of work have been determined the solids´ contents (X) in gels and their supernatants in percentage and their correlation with molecular weight concentration of original HyA solution and the ratio of binding sites on hyaluronan chain and surfactant CTAB. To conclude, decrease in HyA concentration results in higher values of X and vice versa. On the other hand, increase in the value of X with increasing molecular weight of HyA is not so significant. Analogous conclusions have been made for supernatants and the amount of solids in gel. Drying process has been recorded by drying curves. Swelling process has been used for the characterization of gels. The percentage of water that can be absorbed by dried gel, was determined. The results are in agreement with the measurements of solids´ content in gels. In the next part, the correlation between rheological properties of gels and HyA concentration, HyA molecular weight and concentration of CTAB have been studied by the oscillation and flow tests. The samples with the highest molecular weight and concentration have the most viscoelastic character. The flow test confirmed the assumed pseudoplastic behavior of gels. A very interesting trend arose while comparing HyA concentrations and viscosity in stock solutions and gels. Whereas in stock solution viscosity (at low shear rate) is lower with increasing of HyA concentration, the situation was exactly the opposite in gels. The results are in agreement with frequency tests and observed character of gels.

This thesis studies properties of hydrogel, which arises on the basis of electrostatic and hydrophobic interactions between hyaluronan chain and micelles of cationic surfactant. A native sodium hyaluronan at molecular weight 750–1 000 kDa and a cationic surfactant CTAB (cetyltrimethylammonium bromide) were used. This hydrogel was assessed as a material for drug delivery systems. The hydrogels were made by mixing 200mM CTAB with 0.5% hyaluronan, both dissolved in 0.15M aqueous solution of NaCl simulating physiological solution. Methods used in this study were steady-state and time-resolved fluorescence spectroscopy, more accurately time-resolved emission spectra (TRES) and deconvolution of steady-state emission spectra of a whole sample by means of parameters gained from fluorescence intensity decays at a set of wavelenghts. Selected systems were investigated by three fluorescent probes, prodan, laurdan and rhodamine 6G. The first two mentioned probes were in hydrogel localized only within micelles in three different microenvironments. Rhodamine 6G pointed out that in hydrogel the aqueous environment is significantly restricted in comparison to purely micellar solution. In addition, rhodamine informed about less available micelle surfaces, caused by hyaluronan chains occupation. There were no interactions between the probes and hyaluronan chains. Freshly made hydrogels showed almost the same results as after a week of maturation under its supernatant.

Předložená diplomová práce se zabývá přípravou, síťováním a fyzikálně-chemickou charakterizací hydrogelů na bázi polysacharidů. Cílem práce bylo vyvinout elastické filmy, které by mohly být použity pro vlhké hojení ran. Teoretická část shrnuje současné způsoby regenerace měkkých tkání a jejích náhradách (ať už se jedná o přírodní nebo syntetické materiály). Zároveň jsou zdůrazněny základní informace o přírodních polysacharidech (chemická struktura, rozpustnost, tepelná a pH stabilita atd.), jejich modifikace a chemické síťování. Experimentální část je zaměřena na modifikaci přírodní gumy Karaya tak, aby transparentní hydrogely měly nastavitelnou hydrolytickou stabilitu. Vzorky byly analyzovány pomocí FTIR, TGA následované vyhodnocením bobtnání a hydrolytické degradace. Z výsledků vyplynulo, že chemická modifikace zvýšila stabilizaci elastického filmu z přírodního polysacharidu ve vodě až na 25 dní. Díky řízené degradaci a vysoké absorpci vody (85 - 96%) jsou tyto nové hydrogely využitelné především pro vlhké hojení ran (např. popálenin).

Collagen, the most abundant protein of connective tissues, in various forms has a wide applications due to their diverse biological and chemical properties. One of the forms are collagen hydrogels, which are considered very suitable material for applications in tissue engineering, because they are able to provide biodegradable scaffolds that its properties correspond with living tissues. These systems are used for example as scaffold for targeted drug delivery with controlled release, in combination with cells can be used for the regeneration and reconstruction of tissues and organs. Heating the aqueous solution of collagen leads to spontaneous self-assembly process to variously distributed fibrillar structures, which are at a later stage of fibrillogenesis prerequisite for creating a three-dimensional supporting network, which is the basic building block of the gel. The resulting properties of the hydrogel depend not only on its structure, but also on the conditions which cause self-assembly process. Hydrogels were performed at 37 ° C and physiological pH. Studied structural variable was the concentration of collagen. So far, for the research of self-assembly were used spectrometric methods, which only provide information about kinetics of morphogenesis. In this work to study the kinetics of collagen I self-assembly were used rheological methods, which additionally give information about viscoelastic properties of the resulting material. The obtained experimental data confirmed two-step process of collagen I fibrillogenesis consisting of nucleation and growth process. Rheological hydrogels collagen behaved as a nonlinear yield-pseudoplastic. An attempt was made to molecular interpretation of the results. Using two-parametric Avrami equation was determined the rate of self-assembly for each concentration of collagen and the value of Avrami exponent determining the shape of produced units. The prepared hydrogels were subjected to increasing shear stresses (strain amplitude, shear rate). Larger amplitudes leads to collapse of the hydrogel structure, which is able to again partially regenerated.