doktorska disertacija
Urška Gradišar Centa (Author), Maja Remškar (Mentor)

Abstract

Inficirane kontaktne površine predstavljajo enega od ključnih vzrokov za širjenje okužb. Biocidna sredstva za zdravljenje okužb, kot so antibiotiki, izgubljajo svojo učinkovitost zaradi razvoja antibiotske odpornosti mikroorganizmov. Za veliko različnih nanomaterialov kovinskih oksidov, kot so ZnO, TiO2, CuO, srebrovi in zlati nanodelci, molibdenovi ter volframovi oksidi, je bila dokazana protimikrobna aktivnost. Z namenom preprečevanja kolonizacije mikroorganizmov in tvorbe biofilma na različnih površinah je pomemben razvoj polimernih nanokompozitnih materialov z nespecifičnim mehanizmom protimikrobnega delovanja in primernimi fizikalno-kemijskimi lastnostmi. V ta namen sem razvijala polimerne nanokompozite na osnovi inertnega, v vodi netopnega polimera PVDF-HFP in vodotopnih polimerov PEO in PVP ter nanožic MoO3 s protimikrobno aktivnostjo. Raziskala sem fizikalno-kemijske in mikrobiološke lastnosti MoO3 nano in mikro delcev ter v sodelovanju določila koncentracije v vodi raztopljenega MoO3, ki niso strupene za človeške kožne celice. Prvi polimerni nanokompozit v sestavi PVDF-HFP/PEO/MoO3 je pokazal protimikrobno delovanje proti bakteriji Staphylococcus epidermidis, vendar je bil film z nehomogeno dispergiranim MoO3 podvržen zvijanju pri sterilizaciji z UV žarki, prisotnost polimera PEO pa je delno vzpodbujala rast bakterij. Zato sem zamenjala PEO s PVP in pripravila drugi nanokompozit PVDF-HFP/PVP/MoO3, ki ima hidrofilno, nanostrukturirano, pozitivno nabito površino in izkazuje protimikrobno aktivnost na bakterije (Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa), plesen (Penicilium verrucosum) ter kvasovki (Pichia anomala, Candida albicans). Del polimera PVDF-HFP ob prisotnosti PVP v kompozitu kristalizira v β-fazo, MoO3 pa poveča termično stabilnost polimerne osnove. Raztapljanje nanožic MoO3 ob prisotnosti vode, pri čemer nastaja kislo okolje, povzroča hidrolizo PVP polimera in s tem aktivacijo sekundarnega protimikrobnega mehanizma preko sproščanja amonijevih soli. Za karakterizacijo morfoloških lastnosti površine sta bili uporabljeni elektronska vrstična mikroskopija (SEM) in mikroskopija na atomsko silo (AFM). Dinamiko raztapljanja sem spremljala z merjenjem vrednosti pH in prevodnosti raztopine ter s spektrofotometrijo (UV-Vis). Površinske, strukturne in mehanske lastnosti nanokompozita sem določila z meritvami omočitvenega kota, zeta potenciala, ramansko spektroskopijo, dielektričnimi meritvami in z dinamičnim mehanskim analizatorjem (DMA). Iz tega nanokompozita smo izdelali mikro in nanovlakna z metodo elektropredenja s potencialno uporabo v protimikrobnih zračnih filtrih ter jih okarakterizirali z metodami ramanske spektroskopije in elektronske mikroskopije.

Keywords

molibdenovi oksidi;nanožice;polimerni nanokompoziti;površinske lastnosti;elektropredena nanovlakna;protimikrobna aktivnost;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [U. Gradišar Centa]
UDC: 620.3:661.877:579.24(043.3)
COBISS: 68720899 Link will open in a new window
Views: 433
Downloads: 129
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Other data

Secondary language: English
Secondary title: Polimerni nanokompoziti na osnovi biološko ustreznih polimerov in nanožic molibdenovih oksidov
Secondary abstract: Infected contact surfaces are an important source for spread of infections. Biocidal agents for the treatment of infections, such as antibiotics, lose their effectiveness due to the development of antibiotic resistance of microorganisms. Antimicrobial activity has been demonstrated for many different nanomaterials of metal oxides, such as ZnO, TiO2, CuO, silver and gold nanoparticles, molybdenum and tungsten oxides. In order to prevent the colonization of microorganisms and the formation of biofilm on various surfaces, the development of polymeric nanocomposite materials with a non-specific mechanism of antimicrobial action and suitable physicochemical properties is important. For this purpose, I developed polymer nanocomposites based on inert, water-insoluble PVDF-HFP polymer and water-soluble polymers, PEO and PVP, and with the addition of MoO3 nanowires with antimicrobial activity. I investigated the physicochemical and microbiological properties of MoO3 nano and micro particles and, in collaboration, determined the concentrations of dissolved MoO3 in water that are not toxic to human skin cells. The first polymer nanocomposite in the composition of PVDF-HFP/PEO/MoO3 showed antimicrobial activity against the bacteria Staphylococcus epidermidis, but the film with inhomogeneously dispersed MoO3 bent during UV sterilization, and the presence of PEO polymer partially stimulated growth. Therefore, I replaced PEO with PVP and prepared a second polymer nanocomposite PVDF-HFP/PVP/MoO3, which has a hydrophilic, nanostructured, positively charged surface and exhibits antimicrobial activity against bacteria (Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa), mould (Penicilium verrucosum) and yeasts (Pichia anomala, Candida albicans). Part of the PVDF-HFP polymer in the presence of PVP in the composite crystallizes in the β-phase, while MoO3 increases the thermal stability of the polymer matrix. Dissolution of MoO3 nanowires in the presence of water, creating an acidic environment, causes the hydrolysis of the PVP polymer with release of ammonium salts, which represents the secondary antimicrobial mechanism. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the morphological properties of the new nanocomposite surface. Dissolution dynamics was monitored by measuring the pH and conductivity of the solution, and by spectrophotometry (UV-Vis). The surface, structural, electric and mechanical properties of the nanocomposite were determined by measuring the wetting angle and zeta potential, by Raman spectroscopy, dielectric measurements and dynamic mechanical analysis (DMA). Micro and nanofibers were fabricated from this nanocomposite by the electrospinning method with potential use in antimicrobial air filters and characterized by Raman spectroscopy and electron microscopy methods.
Secondary keywords: molybdenum oxide nanowires;polymer nanocomposites;surface properties;electrospun nanofibers;antimicrobial activity;
Type (COBISS): Doctoral dissertation
Study programme: 0
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: 150 str.
ID: 13066515