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Membrane modeling in a single-channel microfluidic chip
Tesák, Petr ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
This work deals with the modelation of artificial cellular membranes in a single channel microfluidic chip. It describes the conditions under which the model membranes are created in channels that are of three different widths. A new method of filling such chips was developed where it is possible to check if the chip is ready to use and at the same time fill it up with saline solution. Furthermore data based on the number of created and burst membranes in microfluidic chips was processed. This statistic takes into consideration the state of these artificial membranes in correlation with all of the chosen sizes and flow rates. Altough there were many complications while gathering this data it is still possible to use it to describe all the benefits and disadvantages of these channels.
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Gel-forming substances of natural cosmetics
Prokopová, Pavla ; Smilek, Jiří (referee) ; Pekař, Miloslav (advisor)
This bachelor thesis is focused on hydrogels preparation for natural cosmetics also it focused on those prepared hydrogels. The aim of the experimental part is to specify physical and chemical properties of hydrogels prepared from commercially available polysaccharides, which agree with conditionals of natural cosmetics standards. First phase of practical part was to prepare and optimize the preparation procedure of individual hydrogels and determine their optimal concentration for use in their characterization. The second phase was the actual preparation of samples for rheometric determination. The last stage was the rheometry itself. The four raw materials selected directly from the CPK Standards were xanthan gum, guar gum, tragacanth gum and gum arabic. The results clearly demonstrated that the best raw material for the preparation of natural hydrogel is xanthan gum. On the other hand, hydrogel from gum arabic is almost impossible to prepare.
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Fluorescence correlation spectroscopy in the study of the properties of colloidal systems
Marková, Kateřina ; Lehocký, Marián (referee) ; Kapusta, Peter (referee) ; Pekař, Miloslav (advisor)
Because of their properties, hydrogels are a highly sought-after matrix for medical purposes. These properties are often conditioned by the structure, therefore the emphasis is put on a precisely defined polymer network. In the presented dissertation, different types of hydrogels were researched using fluorescence correlation spectroscopy (FCS) in conjunction with microrheology. The combination of aforementioned methods is rarely used when determining the properties of hydrogels, and therefore, the method had to be standardized and optimized. For these purposes, fluorescently labeled silicate nanoparticles with a neutral surface charge were selected. In the course of the method optimization, the limits of the device were discovered within which the measured diffusion coefficients could still be considered valid. Furthermore, we have determined the parameters that affect the MSD curve and thus also the correctness of the actual measured data. An aqueous solution of agarose was chosen as a model colloidal system, as it ranges from a viscoelastic liquid to a solid hydrogel depending on the concentration. On this colloidal system, the diffusion properties of the nanoparticles used were tested as well as the structural properties of the system itself. Limit concentrations were found when the diffusion coefficient could no longer be detected using the selected method. The limit was successfully partially extended by adjusting the correlation time, however, the dispersion of the diffusion coefficient values was very high in such case. The values measured in this way were compared with the calibration-free method of bifocal fluorescence correlation spectroscopy (2f–FCS). Furthermore, changes in the diffusion coefficient were determined depending on the type of sample preparation. Alongside these experiments, image analysis was also performed, which provided interesting results in conjunction with FCS. The last experiment, which provided information about the properties of both the embedded nanoparticles and the polymer system, consisted of washing out of the particles from the hydrogel structure. The maximum entropy method with an analysis using log-normal distribution of diffusion coefficients was selected as the last and the most advanced polymer network analysis of the, which defined the system in a new and an alternative way. The results obtained using these advanced analyses were similar to the data calculated using the mathematical model of anomalous diffusion. The description of properties using rheological modules was a completely new approach. The properties were obtained using a series of conversions from the measured autocorrelation curve. Therefore, a rheological module obtained from microrheological data was the output of the approach. The shape of the curve is comparable to classical (macro)rheology, but the numerical values are lower by an entire order of magnitude. The smallest particles in the entire concentration range behaved as if they were in a purely viscous environment while the largest particles defined the behavior of the system depending on the concentration from very viscous to viscoelastic. The last type of measurement was the study of hyaluronan using selected nanoparticles and its fluorescently labeled analogue. All the methods that were used in the study of agarose hydrogel were applied to the viscoelastic system of hyaluronan to verify their applicability.
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Study of the interaction of lung surfactant with selected polymers
Suchá, Klára ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
This thesis deals with the study of interactions between pulmonary surfactant (Curosurf) and selected polymers (N,N,N-trimethylchitosan, polyvinylpyrrolidone, sodium hyaluronate). This work also focuses on the inactivation of lung surfactant using bovine serum albumin, which causes an increase in the surface tension of the surfactant, whereby the inactivated surfactant is unable to fulfill its function in the lungs. The addition of polymers to this mixture has been shown to be an effective means of restoring the surface tension of the surfactant. First of all, this work focuses on finding the optimal concentration ratios of polymer and Curosurf, at which their mutual interaction occurs. The method of dynamic light scattering was used to obtain optimal ratios. In the second part, the work is devoted to the determination of surface tension using a du Noüy ring tensiometer. It was found that the addition of all selected polymers led to a reduction of the surface tension of the inactivated surfactant to values close to native Curosurf. This work provided useful information to understand the mechanism of lung surfactant surface tension recovery.
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Migration of pharmaceuticals in soil systems
Janebová, Denisa ; Pekař, Miloslav (referee) ; Klučáková, Martina (advisor)
The increasing use of drugs leads to their frequent occurrence in the environment, which poses a risk not only because it can lead to the proliferation of antibiotic-resistant bacterial strains, but also because it can threaten human health. Therefore, this work focuses on the issue of the occurrence and behaviour of two antibiotics in soil, specifically tetracycline and sulfamethoxazole. Due to the presence of soil organic matter, it is believed that the soil can partially prevent the spread of drugs that enter the environment. The diploma thesis involved conducting diffusion experiments in soil columns under real conditions to determine the effective diffusion coefficients of tetracycline and sulfamethoxazole in three extraction agents. Sorption and desorption processes were also conducted in the individual layers of the soil column. The concentrations of the leachates were measured using UVVis spectrometry and liquid chromatography, while FTIR spectrometry was used to confirm the presence of the bound drug in the soil column.
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Micro/macro-scale investigation of the viscoelastic properties of hydrogel materials
Obrusníková, Klára ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
Tato diplomová diplomová práce byla zaměřená na srovnání mezi mikroreologickými metodami a makroreologickým přístupem, zejména při charakterizaci hydrogelů. Dynamický rozptyl světla, fluorescenční korelační spektroskopie a optická pinzeta byly vybrány jako mikroreologické techniky, zatímco oscilační reometrie sloužila jako makroreologický nástroj. Výsledky z dynamického rozptylu světla a fluorescenční korelační spektroskopie pro hydrogely agarózy a gellanu byly porovnány s reometrií a mezi sebou. Hodnoty viskoelastických modulů získané z mikroreologických měření byly výrazně nižší než ty získané pomocí makroreologie. Jak dynamický rozptyl světla, tak fluorescenční korelační spektroskopie nabízejí širší škálu měřitelných frekvencí než reometrie, ale obě metody mají své limitace při charakterizaci hydrogelů. U dynamického rozptylu světla dochází k odrazu světla od gelové sítě, což způsobuje šum a zhoršuje kvalitu získaných výsledků. Fluorescenční korelační spektroskopie, přes svou vyšší specifitu, vykazuje jen velmi malé rozdíly mezi vzorky různých koncentrací. Optická pinzeta je na Fakultě chemické novou metodou, a byla provedena pouze kalibrační měření. Tuhost optické pasti, důležitá hodnota pro kalibraci optické pinzety, byla stanovena pro roztoky glycerolu.
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Isolation of photosystem II particles and their characterization
Svitačová, Denisa ; Pekař, Miloslav (referee) ; Venerová, Tereza (advisor)
This master's thesis deals with the isolation and characterization of spinach thylakoid membranes and photosystem II particles. Based on the research, two procedures were chosen for the isolation of spinach thylakoid membranes and photosystem II particles with an emphasis on preserving their native properties. Subsequently, the characterizations were carried out, focusing on the spectroscopic properties of the isolated samples. UV-VIS spectrometry was used to determine the ratio of chlorophyll a to chlorophyll b in samples of thylakoid membranes and photosystem II particles. The success of the isolations was confirmed by fluorescence methods. The excitation and emission spectra of the samples were measured by the steady-state fluorescence spectroscopy, and the fluorescence lifetimes of the samples of thylakoid membranes and photosystem II particles were determined by time-resolved fluorescence. The isolated samples were afterwards visualized with a fluorescence microscope with a CCD camera and the FCS technique.
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Transport and mechanical properties of hybrid hydrogel networks based on gellan
Sokolínský, Jan ; Pekař, Miloslav (referee) ; Kalina, Michal (advisor)
This diploma thesis deals with the characterization of the mechanical and transport properties of gellan based hybrid hydrogels. As part of this work, the process of optimizing the preparation of gellan-poly(vinylalcohol) IPN hydrogel was first studied with an emphasis on the repeatability of the preparation due to the preservation of mechanical properties of the hydrogel. Then, both on the gellan hydrogels themselves and on selected IPN compositions, the effect of various additives was studied (specifically, the effect of the addition of a plasticizer and the effect of cross-linking by polyvalent ions). Based on these tests, a set of samples was selected, on which dynamic mechanical analysis, swelling and drying experiments were additionally measured. At the end of this diploma thesis, the transport properties of selected hydrogel compositions were also studied. The tests conducted in this thesis revealed that both the formation of a dual network and the addition of the mentioned additives allow us to influence the studied properties.
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Utilization of novel strategies of alginate crosslinking in the development of next-generation bioinoculants
Gašparová, Dominika ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
Tato diplomová práce se zaměřuje na různé strategie síťování alginátu, s cílem posunout vpřed vývoj bioinokulantů nové generace. Zkoumání různých strategií gelování se aplikuje na pět komerčně dostupných alginátů a izolovaný bakteriální alginát. Experimenty zahrnující přípravu alginátového makrogelu sloužily ke stanovení výskytu a kvality síťování, které byly analyzovány amplitudovými testy. Výběr vhodných síťovacích činidel a stanovení jejich optimálních koncentrací byly klíčovými cíli. Síťovací činidla, která byla vybrána jako vhodná pro makro- i mikroenkapsulační procesy, byly ty obsahující chlorid zinečnatý, chlorid hlinitý, chlorid barnatý, síran vápenatý a chlorid železitý. Optimální podmínky síťování byly stanoveny při teplotě 7~°C a optimální délka doby síťování v rozmezí od 30 do 120 minut. Byly provedeny komparativní analýzy šesti vybraných síťovacích činidel a to prostřednictvím analýzy mechanických vlastností skrz squeeze test, termogravimetrickou analýzou, botnáním gelu a obrazovou analýzou. Síťování barnatým síťovacím činidlem prokázalo slibné výsledky při zachování obsahu vody během rehydratace, zatímco sítování zinečnatým síťovacím činidlem dosáhlo nejvyššího obsahu sušiny. Obrazová analýza odhalila menší gelové perly tvořené síťovacími činidly s obsahem hliníku a barya, což naznačuje jejich účinnost. Mikroenkapsulované gelové perly, zejména ty síťované s baryem, prokázaly potenciál díky jejich menší velikosti. Vrcholem pokusů bylo síťování bakteriální kultury, kde hliníková a barnatá síťovací činidla dosahovala nejmenších gelových perel. Obzvlášť síťování barnatým činidlem dosahovalo nejmenších velikostí s nejmenší odchylkou, indikujíc jeho efektivitu.
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Computer modeling of diffusional transport in hydrogel
Koláček, Jakub ; Sedláček, Petr (referee) ; Pekař, Miloslav (advisor)
This thesis focuses on the design of models applicable to the simulation of particle motion in a viscoelastic environment in COMSOL Multiphysics. Two approaches have been chosen for the design of these models: the first is the design of a geometry representing the porous structure of hydrogels and the second is the implementation of viscoelasticity using the mathematical concept of a continuous environment. Two elementary geometrical models are presented in this work – a three-dimensional periodic lattice and a spherical volume model. Furthermore, the possibilities of implementing the generalized Langevin equation in COMSOL Multiphysics are explored by using the interface for custom partial differential equations, by adding an auxiliary dependent variable, or by defining a custom external function written in the C language. The proposed geometric models did not prove to be suitable for the simulation of viscoelastic environment. An implementation using an external function seems to be the most promising, as it offers the most customization possibilities, and its implementation reflects the theoretical foundations. The thesis also includes a custom add-in written for COMSOL Multiphysics to facilitate the evaluation of simulation data and a modified Python script to calculate the complex shear modulus from MSD data.
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