Iskanje po katalogu digitalne knjižnice

Opis: This study involved oxygen plasma activation of PVC and its effect on alginate coating adhesion, analyzed using a quartz crystal microbalance with dissipation (QCM-D). The results demonstrated improved adhesion of alginate on plasma-activated PVC due to an increase of oxidized functional groups. Wettability measurements, conducted using optical contact angle goniometry and QCM-D, showed a significant increase in the wettability of PVC after alginate coating, with contact angles decreasing from 81.4 ± 1.1◦ to 37.3 ± 3.1◦ 3D-profilometry mapping revealed a uniform distribution of alginate on the PVC film. Real-time antifouling studies using QCM-D with two model proteins, bovine serum albumin and bovine fibrinogen, were performed to elucidate the surface interactions involved in protein inhibition. The results indicated a substantial reduction in protein adhesion on alginate-coated PVC. This reduction in protein adhesion is attributed to the high hydrophilicity of the alginate coatings and partial removal of the alginate, which together contribute to poor protein adhesion. This comprehensive approach advances the development of effective solutions for mitigating biofilm-related issues on PVC-based medical devices, offering significant implications for improving patient outcomes.
Ključne besede: alginate, coatings, polyvinyl chloride, biofouling, quartz crystal microbalance, protein adhesion
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 8
Celotno besedilo (6,24 MB)
Gradivo ima več datotek! Več...

Opis: A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.
Ključne besede: polymer, chitosan immobilization, adhesion, plasma-surface modification, biopolymers
Objavljeno v DKUM: 05.12.2024; Ogledov: 0; Prenosov: 3
Celotno besedilo (6,47 MB)
Gradivo ima več datotek! Več...

Opis: Protein adhesion and cell response to plasma-treated polymer surfaces were studied. The polymer polyethylene terephthalate (PET) was treated in either an oxygen plasma to make the surface hydrophilic, or a tetrafluoromethane CF4 plasma to make the surface hydrophobic. The plasma source was radiofrequency (RF) discharge. The adsorption of albumin and other proteins from a cell-culture medium onto these surfaces was studied using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The cellular response to plasma-treated surfaces was studied as well using an MTT assay and scanning electron microscopy (SEM). The fastest adsorption rate was found on the hydrophilic oxygen plasma-treated sample, and the lowest was found on the pristine untreated sample. Additionally, the amount of adsorbed proteins was higher for the oxygen-plasma-treated surface, and the adsorbed layer was more viscoelastic. In addition, cell adhesion studies support this finding because the best cell adhesion was observed on oxygen-plasma-treated substrates.
Ključne besede: oxygen and fluorine plasma treatment, polymer surface modification, protein adsorption, cell adhesion, quartz crystal microbalance, QCM
Objavljeno v DKUM: 22.06.2017; Ogledov: 1312; Prenosov: 456
Celotno besedilo (2,39 MB)
Gradivo ima več datotek! Več...

Opis: The last two decades have been determined by the development in the field of tissue engineering. Beside the constant progress in new biomaterials and scaffold fabrication methods, currently the main focus is to understand scaffolds biocompatibility. In our thesis, physical aspects of scaffold biocompatibility were studied by correlating molecular to macro scale physical properties of scaffolds with cell attachment and cell growth. In order to focus on scaffold physical properties, scaffolds were prepared by the same chemical composition of natural polymer gelatin excluding biochemical effects on the cell response. Scaffold with different physical properties were obtained by changing the temperature, pH and crosslinker degree during the cryogelation and populated by the fibroblast cells. Advanced experimental biophysical methods were applied to determine the polymer mobility via electron paramagnetic resonance (EPR) with spin labelling, the scaffold mechanical properties via rheometry, dynamic mechanical analysis (DMA) and nanoindentation using atomic force microscope (AFM) and the scaffold porosity via confocal fluorescence microscopy (CFM). The anisotropy of the molecular mobility of the side chains of polymers in the crosslinked gelatin structure was found to correlate with the initial cell growth (throughout the first week) the best of all the physical properties measured. About five times less efficient cell growth was measured on the scaffolds with highly mobile, spatially nonrestricted dynamics of the polymer side chains, in comparison with cell growth on the scaffolds with the restricted rotational motion of polymers. The result indicates that cells identify and respond to the degree of polymer mobility, where partially immobile phase is necessary for efficient cell attachment and efficient cell growth. So far, the molecular mobility of polymers constituting tissue engineering materials has never been studied thoroughly with respect to its influence on cell response, and therefore may represent a new experimental approach in understanding biocompatibility. To further understand cell-scaffold interaction, the study focused also on the first events during cell attachment - bond formation between the cell surface proteins and the specific binding sites on the material. In our thesis, cell adhesion dynamics was investigated in real-time on the surfaces of gelatin scaffolds with different physical properties using spatially-controlled cell manipulation by the optical tweezers and the confocal fluorescence microscopy detection. Our goal was to elucidate, if the adhesion dynamics can be correlated with cell growth and if it can be dependent on the scaffold polymer molecular mobility. Quantitative characterization of the optical tweezers force applied during cell-scaffold adhesion analysis was done by viscous drag force calibration and dynamic cell sequential trapping of individual cells. The maximal force on a trapped cell not causing the thermal damage was measured up to 200 pN, with nearly linearly increasing force profile across the cell towards the plasma membrane. By submicron spatial resolution of cell manipulation, we managed to quantify probability of cell adhesion, cell adhesion strength and mechanism of cell attachment, including the formation of the membrane tethers, which slow down the adhesion process. Adhesion strength was classified according to the displacement of the attached cell under the force of optical tweezers measured in the direction of the scaffold surface.Cell adhesion was shown to significantly correlate with cell growth in the first days of culture, while the adhesion itself seems to be dependent on the molecular mobility of surface polymers. The result indicates that the interactions during the first seconds may markedly direct further cell response. The developed methodology for cell adhesion analysis on the surfaces of 3D scaffolds serves as a good tool to forecast scaffold biocompatibility.
Ključne besede: polymer molecular mobility, mechanical response, morphology, scaffold biocompatibility, cell growth, single cell manipulation, cell adhesion dynamics, optical tweezers, electron paramagnetic resonance, dynamical mechanical analysis, nanoindentation, fluorescence microscopy and microspectroscopy
Objavljeno v DKUM: 06.10.2015; Ogledov: 2496; Prenosov: 181
Celotno besedilo (5,95 MB)