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Rheological properties and biodegradation of Poly (3-hydroxybutyrate-co-4-hydroxybutyrate)
Černeková, Nicole ; Obruča, Stanislav (oponent) ; Kovalčík, Adriána (vedoucí práce)
This diploma thesis deals with the characterization of rheological properties and biodegradation of a poly(3-hydroxy-co-4-hydroxybutyrate), a copolymer produced by a strain of Cupriavidus malaysiensis. The theoretical part focuses on the rheology and degradation of polymers in general. It also contains the basic characteristics of polyhydroxyalkanoates and deals in more details with the description of the studied copolymer, its properties, synthesis, decomposition and possibilities of its applications. In the experimental part, the given copolymer was investigated in its native form and also in the form of copolymer mixtures filaments, which were enriched with additives (stabilizers and plasticizers). In terms of rheology, the samples showed pseudoplastic behaviour, which was slightly limited by the plasticization of the material. The highest thermal stability observed as a function of changes in complex viscosity over time was observed in a sample of a copolymer mixture containing stabilizers and plasticizer Citrofol BII. The plasticization also caused significant changes in thermal properties, especially crystallinity, which decreased compared to the native copolymer. In vitro degradation studies of samples in the form of films prepared by dissolving copolymer mixtures in chloroform were performed in phosphate buffer with lipase, in simulated body fluid and in synthetic gastric juice. The course of the process itself was characterized by the method of determining the molecular weight (SEC-MALLS) and the weight loss over time (gravimetrically). The results showed that the analysed samples are subject to degradation in all used environments. The most considerable molecular weight loss after 105 days (76 %) was observed in the sample containing stabilizers and plasticizer Citrofol BII in the environment of synthetic gastric juice. The most extensive gravimetric weight loss was attributed to the sample with stabilizers and without plasticizers, in the environment of phosphate buffer with lipase, specifically by 79%.
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Release of active substances from porous structures based on poly(3-hydroxybutyrate) (PHB)
Černeková, Nicole ; Veselá, Mária (oponent) ; Kovalčík, Adriána (vedoucí práce)
This bachelor thesis deals with the study of the release of active substances from porous structures based on poly(3-hydroxybutyrate) (P3HB). The theoretical part describes the basic characteristics of polyhydroxyalkanoates, their effect on the organism and method of electrospinning. In the experimental part, solutions of poly(3-hydroxybutyrate) in a solvent mixture of dichloromethane and chloroform were electrospun in three different ratios. The morphology of the formed fibrous porous structures was assessed by scanning electron microscopy, based on which the active substance, the antibiotic Levofloxacin, was incorporated into suitable structures. Antimicrobial activity of the antibiotic released from prepared porous structures was tested by the agar diffusion method against gram-negative bacteria Escherichia coli and Serratia marcescens, the gram-positive bacterium Micrococcus luteus and against the yeast Candida glabrata. The results showed a significant antimicrobial effect of the prepared samples against all bacterial cultures, in the case of the culture of yeasts, no zones of inhibition occurred. Next, the course of the active substance release from the prepared electrospun meshes was studied spectrophotometrically depending on the morphological structure. It was found that the active substance was successfully incorporated into electrospun fibers and the course of the drug release depended on the morphology of P3HB electrospun meshes.
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Rheological properties and biodegradation of Poly (3-hydroxybutyrate-co-4-hydroxybutyrate)
Černeková, Nicole ; Obruča, Stanislav (oponent) ; Kovalčík, Adriána (vedoucí práce)
This diploma thesis deals with the characterization of rheological properties and biodegradation of a poly(3-hydroxy-co-4-hydroxybutyrate), a copolymer produced by a strain of Cupriavidus malaysiensis. The theoretical part focuses on the rheology and degradation of polymers in general. It also contains the basic characteristics of polyhydroxyalkanoates and deals in more details with the description of the studied copolymer, its properties, synthesis, decomposition and possibilities of its applications. In the experimental part, the given copolymer was investigated in its native form and also in the form of copolymer mixtures filaments, which were enriched with additives (stabilizers and plasticizers). In terms of rheology, the samples showed pseudoplastic behaviour, which was slightly limited by the plasticization of the material. The highest thermal stability observed as a function of changes in complex viscosity over time was observed in a sample of a copolymer mixture containing stabilizers and plasticizer Citrofol BII. The plasticization also caused significant changes in thermal properties, especially crystallinity, which decreased compared to the native copolymer. In vitro degradation studies of samples in the form of films prepared by dissolving copolymer mixtures in chloroform were performed in phosphate buffer with lipase, in simulated body fluid and in synthetic gastric juice. The course of the process itself was characterized by the method of determining the molecular weight (SEC-MALLS) and the weight loss over time (gravimetrically). The results showed that the analysed samples are subject to degradation in all used environments. The most considerable molecular weight loss after 105 days (76 %) was observed in the sample containing stabilizers and plasticizer Citrofol BII in the environment of synthetic gastric juice. The most extensive gravimetric weight loss was attributed to the sample with stabilizers and without plasticizers, in the environment of phosphate buffer with lipase, specifically by 79%.
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Release of active substances from porous structures based on poly(3-hydroxybutyrate) (PHB)
Černeková, Nicole ; Veselá, Mária (oponent) ; Kovalčík, Adriána (vedoucí práce)
This bachelor thesis deals with the study of the release of active substances from porous structures based on poly(3-hydroxybutyrate) (P3HB). The theoretical part describes the basic characteristics of polyhydroxyalkanoates, their effect on the organism and method of electrospinning. In the experimental part, solutions of poly(3-hydroxybutyrate) in a solvent mixture of dichloromethane and chloroform were electrospun in three different ratios. The morphology of the formed fibrous porous structures was assessed by scanning electron microscopy, based on which the active substance, the antibiotic Levofloxacin, was incorporated into suitable structures. Antimicrobial activity of the antibiotic released from prepared porous structures was tested by the agar diffusion method against gram-negative bacteria Escherichia coli and Serratia marcescens, the gram-positive bacterium Micrococcus luteus and against the yeast Candida glabrata. The results showed a significant antimicrobial effect of the prepared samples against all bacterial cultures, in the case of the culture of yeasts, no zones of inhibition occurred. Next, the course of the active substance release from the prepared electrospun meshes was studied spectrophotometrically depending on the morphological structure. It was found that the active substance was successfully incorporated into electrospun fibers and the course of the drug release depended on the morphology of P3HB electrospun meshes.
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