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Characterization of hydrogels based on photocross-linked derivative of hyaluronan
Hekrlová, Veronika ; Smilek, Jiří (referee) ; Klučáková, Martina (advisor)
This bachelor thesis focuses on characterization of hydrogels based on photocross-linked Tyramine-modified hyaluronan (HA-Tyr). In the first part of the work, swelling of gels in saline and porcine plasma was examined, in which the hydrogels swell significantly less. The second part of the thesis is focused on rheology. First, dependence of the apparent viscosity of precursor solutions on shear rate was tested. The apparent viscosity increases with the concentration of derivative and Mw. This trend can also be observed when measuring viscoelastic properties (the elastic modulus) in oscillation mode (strain sweep test). The elastic modulus can also be affected by using a higher concentration of the photoinitiator riboflavin (RF), higher radiation intensity or by longer exposure times, although the material can be degraded. The work also includes an ATP bioluminescence method cytotoxicity test, which proved that the methods used are safe for in situ application.
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Preparation and characterization of novel application forms of humic substances in combination with water sorbents
Nováčková, Táňa ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
This bachelor’s thesis discusses an applicability of hydrogel forms-based composite materials of humic acids and commercial water sorbent. According to the literature review, methods of incorporation of humic acids into commercial sorbents of water under various conditions and the resulting materials were subsequently characterized. In the characterization, major attention was paid to the determination of the water content and the swelling characteristics. Preparation of the composite materials was directed to use their sorption abilities and ability to control the release of humic substances in agriculture.
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Biodegradable polyurethanes based on poly(ethylene glycol)
Kupka, Vojtěch ; Žídek, Jan (referee) ; Vojtová, Lucy (advisor)
Predložená diplomová práce se zabývá syntézou biodegradabilních polyuretanu (bio-PU) na bázi polyethylenglykolu (PEG-u) a polykaprolaktonu (PCL) pro využití k medicínským úcelum. Cílem práce bylo vyvinout metodiku prípravy elastomerního polyuretanu, ze kterého by se dal v budoucnu pripravit skafold (nosic bunek) použitelný v tkánovém inženýrství pro humánní regenerativní medicínu. Teoretická cást práce shrnuje informace o materiálech využitelných pro zamýšlenou aplikaci. Zahrnuty jsou také techniky prípravy skafoldu, jejich biokompatibilita a charakterizace vlastností výsledného materiálu. Praktická cást je pak zamerena na navržení vhodné metodiky pro prípravu funkcních vzorku obsahujících PEG, PCL, hexamethylen-diisokyanát (HMDI) a ethylhexanoát cínatý jako katalyzátor. U pripravených vzorku byl zjištován vliv jejich složení (predevším ruzný obsah a molekulová hmotnost PEG-u) na botnání a hydrolytickou stabilitu spolecne s testováním mechanických vlastností, sledováním kinetiky sítování a stanovením stupne konverze. Morfologie vzorku byla sledována pomocí optické mikroskopie, chemické složení bylo potvrzeno infracervenou spektroskopií a tepelné vlastnosti byly urceny diferencní kompenzacní kalorimetrií. Vývoj v metodice prípravy ukázal, že je nezbytné odstranit pred syntézou z výchozích látek veškeré necistoty, predevším vodu a kyslík, jinak vznikaly nedokonale zreagované vzorky s velkým obsahem póru ruzných velikostí. Syntéza všech vzorku probíhala pod dusíkovou atmosférou ve dvou krocích, kdy v prvním se pouze homogenizovaly oba polyoly (PEG i PCL) na vakuové lince pri 130 °C a ve druhém pak vznikaly výsledné bio-PU za pridání HMDI pri 65 °C v inertní atmosfére manipulacního boxu. Vzorky pak byly dopolymerovány ve forme pri 65 °C pod dobu 48 hodin v sušárne. Ruzné fyzikální podmínky metodiky vedly k príprave jak nepruhledných bílých filmu, tak i vzorku s viditelnou separací fází až po flexibilní transparentní filmy. Pozorování optickým mikroskopem vzorku s fázovou separací prokázalo prítomnost sférolitické struktury krystalické fáze PCL v amorfní fázi matrice PEG-u. Sledování kinetiky sítování pomocí soxhletovy extrakce potvrdilo maximální konverzi polymerace (96 %) již za 4 h dopolymerování v sušárne. Testování zkouškou v tahu ukázalo, že výrazný vliv na pevnost v tahu má isokyanátový index (pomer NCO/OH skupin). Molekulová hmotnost PEG-u ovlivnovala pevnost v tahu jen u vzorku zcela zesítovaných. Merení botnání vzorku ve vode prokázalo, že s rustem molekulové hmotnosti PEG-u roste i obsah vody (od cca 28 až po 58 hm.%) ve vzorcích. Také degradace filmu ve vode pri 37 °C probíhala dle predpokladu rychleji u vzorku s vyšší molekulovou hmotností PEG-u. V predložené diplomové práci bylo potvrzeno, že množstvím a molekulovou hmotností polyethylenglykolu je možné rídit hydrolytickou stabilitu výsledných biodegradabilních polyuretanových elastomeru.
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Synthesis and Characterization of Multifunctionalized Biodegradable Copolymers
Michlovská, Lenka ; Petrůj, Jaroslav (referee) ; Lehocký,, Marián (referee) ; Vojtová, Lucy (advisor)
Předložená disertační práce shrnuje současné poznatky v oblasti termosenzitivních biodegradabilních kopolymerů, které ve formě vodného solu gelují při teplotě lidského těla. Tyto polymerní materiály jsou použitelné v medicíně pro injekční aplikace jako nosiče léčiv či resorbovatelné implantáty pro regeneraci tkání. V experimentální práci byly pomocí vakuové linky syntetizovány termosenzitivní amfifilní triblokové kopolymery na bázi biodegradabilního hydrofobního polylaktidu a polyglykolidu a biokompatibilního hydrofilního polyethylenglykolu (PLGA–PEG–PLGA). Připravený PLGA–PEG–PLGA kopolymer se dvěma fázovými přechody sol-gel a gel-suspenze byl následně modifikován anhydridem kyseliny itakonové. Výsledný funkcionalizovaný ITA/PLGA–PEG–PLGA/ITA kopolymer obsahuje na koncích řetězců reaktivní dvojné vazby vhodné k další polymeraci či síťování a karboxylové skupiny pro případné modifikace biologicky aktivními látkami. Fyzikální i chemické síťování bylo dále sledováno jak z hlediska poměrů hydrofilního a hydrofobního řetězce, tak i z hlediska množství navázané kyseliny itakonové. Vodné roztoky syntetizovaného ITA/PLGA–PEG–PLGA/ITA kopolymeru gelují v rozmezí teplot 33 - 43 °C. Kritická gelační koncentrace byla 6 % a kritická gelační teplota 34 °C pro kopolymer s poměrem PLGA/PEG = 2,5. Čím je kopolymer více hydrofobní, tím geluje dříve a je více hydrolyticky stabilní. Tuhost gelu stoupá se zvyšujícím se poměrem PLGA/PEG a je závislá na typu rozpouštědla použitého při přečišťování kopolymeru. Připravené ITA/PLGA–PEG–PLGA/ITA makomonomerů byly síťovány pomocí modrého světla bez dalšího síťovadla. Hydrolytická stabilita vzorků modifikovaných pomocí ITA se výrazně zlepšila a zvýšila v přímé úměře jak s rostoucí dobou síťování, tak s množstvím dvojných vazeb na koncích řetězců. Vzorek s 63 mol% ITA síťovaný 40 minut ve vodě zcela zdegradoval po 32 dnech. Protonovou NMR relaxometrií bylo zjištěno, že když vzorek ve vodě nabotnal (po cca 12 hodinách), množství nevázané vody se začalo snižovat a postupně difundovat do kavit na povrchu vzorku a pomalu se měnit na slabě a pevně vázanou vodu na polymerní řetězce. Nicméně, termální stabilita chemicky síťovaných vzorků vzrůstala pouze do 20 minut síťování. Pomocí ATR-FTIR bylo prokázáno, že se přibližně 57 % dvojných vazeb kyseliny itakonové (při vlnové délce 1640 cm-1) přeměnilo na nové jednoduché RR'C-CHR'' vazby při vlnové délce 795 cm-1. Delší čas síťování (nad 30 minut) vedl ke změnám v chemické struktuře pomocí beta-štěpení řetězců a částečné rekombinaci dvojných vazeb. Díky vzniku nových dvojných vazeb v jiných částech řetězce se snížila termální stabilita z 242 °C na 237° C a teplota skelného přechodu z -2,2 na -5.8 °C. Předložená práce popisuje, jak složení polymeru, modifikace funkčními skupinami a fyzikální podmínky ovlivňují fyzikální a chemické síťování připravených amfifilních kopolymerů. Kontrola hydrolytické a termální stability hydrogelů je zapotřebí zejména při uvolňování léčiv a regeneraci tkání.
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Development of New Application Forms of Humic Substances for Agricultural and Environmental application
Kratochvílová, Romana ; Kráčalík, Milan (referee) ; Salaš, Petr (referee) ; Klučáková, Martina (advisor)
The new forms of superabsorbent polymers (SAP) on the base of acrylic acid were developed and studied in this thesis. The SAP are focused on agricultural and environmental applications. While they are applied to the soil, SAP can prevent water losing and they become a reservoir of humidity in case of dry season, moreover in combination with fertiliser they play role of controlled release medium. Eight various samples of SAP were experimentally prepared by networking of partially neutralized acrylic acid. Potassium peroxydisulfate was used as the initiator and N,N–methylenebisacrylamide as the crossing agent. Some of samples contained addition of second monomer of acrylamide. All of them were enriched by fertilisers – natural lignohumate or synthetic NPK or combination of both. The swelling characteristics of prepared samples were investigated in conditions of various ionic strength. The influence of xerogels’ particles size on swelling properties was also observed. The viscoelastic characteristics of hydrogel form of all SAP were determined by using of rotation rheometer. The changing of viscoelastic properties were studied in dependence on time, on freezing and on repeating swelling cycles. On top of that the controlled releasing ability of SAP was tested due to three modelling experiments. The biological activity of all polymer products was tested at the end of the thesis. All samples of SAP were incorporated into the artificial soil and the ability of the water retention in the soil was observed. The growing experiments were running by using of corn plants. The size and the mass of each plant were measured and branching of the root was objectively evaluated by programme Harmonic and Fractal Image Analyzer.
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Humic substances as transport medium for plant nutrition
Vlková, Markéta ; Solná, Irena (referee) ; Klučáková, Martina (advisor)
This bachelor thesis treats about humic matters and their application in agriculture by means of hydrogels transport medium. It studies progressive releasing of substances, which could be used as more common nutrition for plants, prepared from superabsorbent polymers. Research was implemented in collaboration with industrial partners. The substances are synthetically made of sodium Lignohumate and mixture of industrial fertilizer called NPK. Released substances were characterized by using some methods. First, there were measured qualities, which didn’t specify released compounds, like swelling, conductivity, pH and absorption of hydrogels with different wavelengths. More details came with methods ICP-OES and ion chromatography. Hydrogels which contained both mixtures of matters written up, were studied in water solution for 5 weeks and every week all characterization were measured. From the results we can see that both of the mixtures decrease ability of hydrogel’s swelling, mainly NPK. Measuring of absorption showed that the most of the substances released from sodium Lignohumate were from hydrogels without NPK. By other measuring, we noticed realizing of potassium and phosphorus elements. The most of them were from hydrogels containing NPK. By measuring ion chromatography, we found chloride, phosphoric, sulfuric and nitric ions in solution.
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Transport Properties of Thin Films Based on Polyvinylalcohol
Blažková, Dominika ; Smilek, Jiří (referee) ; Kalina, Michal (advisor)
This bachelor thesis deals with the optimization of the preparation of hydrogel thin films based on polyvinyl alcohol (PVA). The first step was to optimize the preparation of films. PVA, with a molecular weight of 130 kDa, was used for the preparation of films and 10 wt.% solutions in ultrapure water were prepared from it. The heating duration time of the solution was set at 1.5 h at 90 °C. This was followed by drying at 50 °C for 24 h. Subsequently, PVA films were also prepared from solutions of methylene blue in water and from solutions of methylene blue in an aqueous NaCl solution. The prepared films were subsequently characterized by measuring their thickness, swelling ability, specific surface area and diffusion properties. The morphology of the PVA films was also visualized by SEM microscopy. All prepared films were smooth and had a very small specific surface area. The transport properties were monitored by the method of release into solution and Methylene blue was used as a probe. Release into 5, 10 and 20 ml of ultrapure water was observed. The results obtained show that the most methylene blue was released into the solution with the greatest volume and the release of methylene blue from the PVA film takes place freely without significant interaction with the matrix of the PVA film.
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Preparation and application of physical hyaluronan gel
Kovářová, Lenka ; Krouská, Jitka (referee) ; Venerová, Tereza (advisor)
Bachelor's work is concerning by research in physical hyaluronan gel area. Research is focusing on its preparation, especially by interaction of hyaluronan (HyA) solution with opposite charged surfactant in physiological solution (0,15 M NaCl). In the first part of work I found out influence of molecular weight, concentration of original hyaluronan solution and the ratio of binding sites on hyaluronan chain and surfactant on amount of solids in gel, expressed in percent. Finally we can say, that this value is not influenced by molecular weight of HyA neither relation of binding sides. On the other side, concentration of original HyA solution has significant influence on amount of solids in gel. There was also researched process of gel swelling, where was set amount of water (in percent) able to take dried gel back. Analogical conclusion has been reached like amount of solids in gel. In other part were researched influence of hyaluronan molecular weight and the ratio of binding sites on hyaluronan chain and surfactant on formation of excimers and spectrum change by fluorescence spectroscopy. Pyrene, 1,3-bis(pyren-1-yl)propane (P3P) and prodan were used as fluorescence probes. Excimer emission showed at P3P, while there was no growth of intensity at 470 nm for pyrene. It was found that molecular weight does not affect the value of the ratio of excimer and monomer probe P3P, or the ratio of the first and third peaks of pyrene. The ratio of binding sites HyA and surfactant influence only relation of excimer to monomer (P3P probe), while influence to relation 1:3 hasn't been noticed for pyrene. I have compared spectrum of developed gel for prodan probe, relevant solid and swelled gel by return. It also served for drying and swelling process visualisation.
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Material characterization of novel hydrogels containing humic substances intended for pharmaceutical and cosmetic applications
Pavlicová, Renata ; Weidlich, Tomáš (referee) ; Sedláček, Petr (advisor)
This thesis is focused on the development and characterization of hydrogels containing humic substances with possible use in cosmetic and pharmaceutical industries. This work follows on the bachelor thesis, theoretical and experimental part is based on already acquired knowledge. The aim of this work was to develop a literature review focusing on the potential use humic gels in practice and also to enhance the consistency of other active ingredients. Based on this literature review, the main aim was to prepare model humic hydrogels with selected active ingredients and their characterization by basic methods of material analysis. These basic methods were especially rheology and visual assessment of consistency during the preparation, then the samples were subjected process of drying and swelling. Experimental results showed considerable influences during the preparation and composition of each sample, which then reflected in their structure and consistency. Furthermore, it was found that the suitable composition and combination of ingredients form hydrogels acceptable characteristics for further use in cosmetic or pharmaceutical applications.
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Study of physical gels with hydrophobic domains
Kovářová, Lenka ; Márová, Ivana (referee) ; Mravec, Filip (advisor)
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.
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