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.
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