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Chemical modifications of hydrogels from natural polysaccharide
Poštulková, Hana ; Žídek, Jan (oponent) ; Vojtová, Lucy (vedoucí práce)
Chemical structure, use and chemical and physical properties of natural polysaccharide gum karaya (Sterculia urens) were summarized in theoretical part of this work. The general goal of the diploma work was modification of original insoluble gum karaya under alkali condition to prepare water soluble sample for further applications. Insolubility of gum karaya is caused by presence of acetyl groups and multivalent ions in the structure of polysaccharide. Optimized conditions for modification process were investigated. Sodium, potassium or ammonium hydroxide, 1 minute to 24 hours of treatment and 0.1 - 3% solution of original gum karaya were used for optimizing the modification process. Original (OGK) and modified (MGK) samples were studied by FTIR to investigate chemical composition. Modified samples A2, B1-7, C1-8 and E1-2 were considered as fully deacetylated because of absence of band at 1725 cm-1 which represents acetyl group. Absence of acetyl groups after modification was also proved by 13C CP MAS NMR. Amorphous character of original gum karaya was determined by XRD. TGA was used to evaluate amount of moisture and thermal stability of original and modified samples. Thermal stability of OGK was higher (280 °C) than of modified samples. Thermal stability of MGK was affected by reaction parameters. Thermal changes in polysaccharide chains were studied by DSC but any significant differences between OGK and MGK were not observed. Mineral composition of original and modified samples was investigated by ICP OES and presence of calcium, potassium and magnesium ions in OGK was confirmed. Molecular weight of modified samples was evaluated by GPC and was approximately 8 million g·mol-1. Rheological measurement for determination of linear viscoelastic region was determined. Effect of NaCl on viscosity of original gum karaya was performed. Viscosity of OGK decreased with higher amount of NaCl. Lower viscosity of OGK is connected with exchange of Ca2+ for Na+ ions and release of the physically bonded structure resulting in higher solubility of OGK in water.
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Sprayable elastic biopolymer hydrogels for wound healing
Waclawiková, Petra ; Nedomová, Eva (oponent) ; Vojtová, Lucy (vedoucí práce)
The main aim of the presented bachelor thesis is focused on the preparation and characterization of sprayable hydrogels from suitable non-toxic substances, in order to develop gels applicable in wound healing management. The theoretical part deals with general properties of hydrogels, methods of their crosslinking and presents selected natural and synthetic materials used for the preparation of hydrogels. It also contains a brief overview of already prepared sprayable hydrogels, which are not yet commercially used. The experimental part describes the selection and use of readily available non-toxic biomaterials and the measurement of the physico-chemical properties of the prepared gels. Gum Karaya, poly(vinyl alcohol) and sodium alginate were selected as the structural polymers together with different physical crosslinkers and additives. The polymers and additives were subjected to solubility test followed by mixing in certain ratios and crosslinked to form preferably transparent hydrogels. Subsequently their optical and rheological properties were valuated. The measurement of optical properties shows that probably gum Karaya affected increasing in both yellowness as well as transparency. By rheological measuring it was demonstrated, that the higher content of gum Karaya reduces the mechanical resistance of the prepared hydrogels. Hydrogel strength reflects both low and high amount of crosslinker where the optimal amount gave the best result. Therefore, the correct ratio of the used substances is the main parameter for obtaining the most effective hydrogel properties suitable for sprayable hydrogel dressings.
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Modification of hydrogel wound dressings by biological active agents
Štrublová, Veronika ; Říhová, Martina (oponent) ; Vojtová, Lucy (vedoucí práce)
The aim of the work is to design and prepare inexpensive hydrogel wound dressing which will protect the wound from microbial infection and will accelerate the healing process. The theoretical part summarises both natural and synthetic polymers, antibacterial and pro-healing agents which are widely used in the biomedical applications. It also contains a brief overview of the phases of the wound healing process. Experimental part of proposed thesis deals with the preparation and characterisation of hydrogel wound dressings with a porous structure consisting of both natural and synthetic polymers including natural polysaccharide Gum Karaya (GK), poly(vinyl alcohol) and poly(ethylene glycol). Prepared freeze-dried hydrogel wound dressings were enriched with selected biological agents – antibacterial selenium nanoparticles and fibroblast growth factor FGF2 representing wound healing protein. A range of physio-chemical techniques was employed to characterised freeze-dried hydrogel dressings. Fourier-transformed infrared spectroscopy with attenuated total reflectance (ATR-FTIR) was used to determinate changes in the chemical structure, biomechanical properties at physiological conditions were evaluated by tensile testing using dynamic-mechanical analysis, morphology was characterised by scanning electron microscopy (SEM) and swelling properties of prepared samples were evaluated by a suitable gravimetric method. Evaluation of antimicrobial properties of GK was carried out by the agar diffusion disk method and the microdilution broth method. Cytotoxicity was quantified based on A) estimating the number of live and dead cells in the extract of GK hydrogel dressings and B) measuring cell proliferation by resazurin assay. In vivo wound healing evaluation were performed in cooperation with Veterinary Research Institute Brno on Large white pig as an animal model. Based on results, samples containing glycerol proved excellent biomechanical properties in both dry and hydrated state. The antimicrobial testing showed the positive synergic effect of GK and selenium nanoparticles on microbial inhibition of all tested G+ strains. In vitro and in vivo evaluation proved enhanced healing ability of the material without causing toxicity to cells. Therefore, novel porous and very stable hydrogel wound dressings are promising materials that can be used in biomedical applications mainly for moist wound healing.
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Novel hydrogels based on polysaccharides for soft tissue regeneration: preparation and characterization
Nedomová, Eva ; Abdellatif, Abdelmohsan (oponent) ; Vojtová, Lucy (vedoucí práce)
Presented diploma thesis deals with preparation, crosslinking and physico-chemical characterization of natural polysaccharide-based hydrogels. The aim of the work was to evolve elastic thin films with potential application for moist wound healing. The theoretical part summarizes the state-of-art about regeneration of soft tissues and their substitutes (synthetic or nature). There are pointed out the basic information about natural polysaccharide gums (chemical structure, solubility, heat and pH stability etc.), its modification and chemical crosslinking. The experimental part is focused on the modification of natural gum Karaya in order to make transparent hydrogels with adjustable hydrolytical stability. Samples were analyzed by FTIR, TGA followed by evaluation of swelling properties and hydrolytical degradation. Based on the results, chemical modification helped to stabilize polysaccharide hydrogels in water up to 25 days which is useful mainly for moist wound healing (e.g. after burns) because of high values of water uptake (from 85 up to 96%).
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Influence of the polymer mixture composition on the properties of polysaccharide fibrous biomaterials
Kavčiaková, Zuzana ; Pavliňáková, Veronika (oponent) ; Vojtová, Lucy (vedoucí práce)
Proposed diploma thesis deals with the preparation and evaluation of the properties of the fibers based on the polysaccharide Gum Karaya and its mixtures with poly(vinyl alcohol), poly(vinyl pyrrolidine) and poly(ethylene oxide). The diploma thesis is divided to the theoretical, experimental and discussion part. The theoretical describes the preparation and characterization of different sized fibers. The experimental involves the preparation of fibers by electrospinning method. Obtained fibers were analysed by means of the Fourier transformed infra-red (FT-IR) spectroscopy, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and gravimetrical method to evaluate the fiber swelling ratio. Electrospun fibers obtained from aqueous solution of organic acids have confirmed to be a suitable material with the sufficiently good fiber diameter and tensile strength.
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Preparation and characterization of modified polysaccharide hydrogels for medical applications
Poštulková, Hana ; Částková, Klára (oponent) ; Lehocký,, Marián (oponent) ; Vojtová, Lucy (vedoucí práce)
This work focuses on comprehensive characterization of naturally insoluble polysaccharide Gum Karaya (GK) in order to contribute to the general knowledge of this not well studied biomaterial. Besides the GK solubilization process, which was studied under different conditions, this work proposes a new hydrogel, which is based on a unique combination of materials including Gum Karaya and protein Silk Fibroin. This approach allows for the utilization of the specific features of each individual material in the given hydrogel system and for the study of their interaction. Hydrogels were prepared without any chemical crosslinkers and were based only on a physical crosslinking of the system. Chemo-physical and biological properties of the prepared hydrogels were evaluated and discussed. Cell culture assays evaluating keratinocytes in contact with the hydrogels suggested good biocompatibility properties and low adhesion between the cells and hydrogels. Furthermore, GK and its mixture with another biopolymer exhibited bacteriostatic properties against selected gram-positive microorganisms, however bactericidal activity was not observed. Results obtained throughout this work suggested that the utilization of Gum Karaya and prepared hydrogels possesses the potential to be used in regenerative medical applications for example as a hydrogel for burnt skin treatment.
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Blue-light crosslinked hydrogels from modified natural gum for medical applications
Waclawiková, Petra ; Michlovská, Lenka (oponent) ; Vojtová, Lucy (vedoucí práce)
The main aims of the presented master’ thesis are focused on the modification of natural gum and its consequential crosslinking via blue or ultraviolet light, in order to develop a sprayable hydrogel applicable for controlled wound healing. The theoretical part of the work deals with the preparation of hydrogels, especially by photopolymerization, and the possibilities of using different light sources for crosslinking. Related to this, the work contains and overview of photoinitiators suitable for the preparation of water-based hydrogels. Thesis introduce examples of functionalization in order to implement a photosensitive functional group into the polymer structure, especially methacrylation. The experimental part of the presented work deals with the preparation and characterization of hydrogels composed of synthetic and natural polymers. The default material was the natural polysaccharide Gum Karaya (GK), which was chemically modified and consequently crosslinked via water-soluble photoinitiator. Chemical modification of Karaya gum saccharide was characterized by two spectroscopic techniques. The attenuated total reflection method of Fourier transform infrared spectroscopy (ATR-FTIR) was used to determine changes in chemical structure. Furthermore, Raman spectroscopy was used as a supplement to the ATR-FTIR method. UV-Vis spectrophotometry was used to evaluate the optical properties of the samples before and after photocrosslinking. The application properties of the synthesized polysaccharide and the prepared hydrogels were tested by the swelling method and the sprayability was verified by rheology. Based on the results, the chemical modification of gum Karaya was successful and it was possible prepare a photocrosslinked hydrogels after the photoinitiator addition.
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Porous hydrogels from natural gum modified with bio-active substances for accelerated wound healing
Černá, Eva ; Brtníková, Jana (oponent) ; Vojtová, Lucy (vedoucí práce)
The main aim of this thesis is to design, prepare and optimize composition of hydrogel dressing for wound healing with skin-like properties. An inexpensive hydrogel dressing with properties that accelerate healing process, supress bacterial infection and support easy handling is supposed to be a result of this work.. The theoretical part is focused on properties of each layer of the skin, polymer materials suitable for wound healing, pro-healing and antimicrobial agents suitable for antimicrobial environment in the wound. The experimental part includes several steps. The first one is optimization of the composition of the porous hydrogel dressing composed of natural polymer, resin Gum Karaya (GK) modified with synthetic hydrophilic gelling polymers and important emollient componentto obtain soft, elastic and transparent films via freeze-drying technique. Films were tested in terms of swelling ratio, hydrolytic stability, transparency, strength in tension in both dry and wet conditions, chemical composition and morphology. The second step includes integration of bioactive antiseptic compound into the structure of the hydrogel, which provides suitable antimicrobial properties for wound healing. Prepared transparent, hydrolytically stable and very tough hydrogel films were found to be effective against both gram-positive and gram negative bacterial strains tested within these work, specifically Staphylococcus aureus methicillin-sensitive, Staphylococcus aureus methicillin-resistant, Staphylococcus epidermidis, Klebsiella pneumoniae, Enterobacter cloacae, Enterococcus faecalis, Pseudomonas aeruginosa, Candida albicans and Escherichia coli. Followed work will be focused on both in vitro and in vivo biocompatibility evaluations.
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Influence of the polymer mixture composition on the properties of polysaccharide fibrous biomaterials
Kavčiaková, Zuzana ; Pavliňáková, Veronika (oponent) ; Vojtová, Lucy (vedoucí práce)
Proposed diploma thesis deals with the preparation and evaluation of the properties of the fibers based on the polysaccharide Gum Karaya and its mixtures with poly(vinyl alcohol), poly(vinyl pyrrolidine) and poly(ethylene oxide). The diploma thesis is divided to the theoretical, experimental and discussion part. The theoretical describes the preparation and characterization of different sized fibers. The experimental involves the preparation of fibers by electrospinning method. Obtained fibers were analysed by means of the Fourier transformed infra-red (FT-IR) spectroscopy, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and gravimetrical method to evaluate the fiber swelling ratio. Electrospun fibers obtained from aqueous solution of organic acids have confirmed to be a suitable material with the sufficiently good fiber diameter and tensile strength.
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Modification of hydrogel wound dressings by biological active agents
Štrublová, Veronika ; Říhová, Martina (oponent) ; Vojtová, Lucy (vedoucí práce)
The aim of the work is to design and prepare inexpensive hydrogel wound dressing which will protect the wound from microbial infection and will accelerate the healing process. The theoretical part summarises both natural and synthetic polymers, antibacterial and pro-healing agents which are widely used in the biomedical applications. It also contains a brief overview of the phases of the wound healing process. Experimental part of proposed thesis deals with the preparation and characterisation of hydrogel wound dressings with a porous structure consisting of both natural and synthetic polymers including natural polysaccharide Gum Karaya (GK), poly(vinyl alcohol) and poly(ethylene glycol). Prepared freeze-dried hydrogel wound dressings were enriched with selected biological agents – antibacterial selenium nanoparticles and fibroblast growth factor FGF2 representing wound healing protein. A range of physio-chemical techniques was employed to characterised freeze-dried hydrogel dressings. Fourier-transformed infrared spectroscopy with attenuated total reflectance (ATR-FTIR) was used to determinate changes in the chemical structure, biomechanical properties at physiological conditions were evaluated by tensile testing using dynamic-mechanical analysis, morphology was characterised by scanning electron microscopy (SEM) and swelling properties of prepared samples were evaluated by a suitable gravimetric method. Evaluation of antimicrobial properties of GK was carried out by the agar diffusion disk method and the microdilution broth method. Cytotoxicity was quantified based on A) estimating the number of live and dead cells in the extract of GK hydrogel dressings and B) measuring cell proliferation by resazurin assay. In vivo wound healing evaluation were performed in cooperation with Veterinary Research Institute Brno on Large white pig as an animal model. Based on results, samples containing glycerol proved excellent biomechanical properties in both dry and hydrated state. The antimicrobial testing showed the positive synergic effect of GK and selenium nanoparticles on microbial inhibition of all tested G+ strains. In vitro and in vivo evaluation proved enhanced healing ability of the material without causing toxicity to cells. Therefore, novel porous and very stable hydrogel wound dressings are promising materials that can be used in biomedical applications mainly for moist wound healing.
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