Synthesis of antibacterial polymeric nanocoatings by chemical vapor deposition method and investigation of antibacterial and cytotoxic properties of these coatings

In this thesis, polymers with antibacterial properties were synthesised on different substrates by initiated chemical vapour deposition (iCVD) and plasma enhanced chemical vapour deposition (PECVD) techniques. In the first part polymeric thin films with antibacterial properties, biocompatibility, chemical and mechanical strength, high adhesion and high biocompatibility were coated on glass, fabric and polyethylene terephthalate (PET) substrate surfaces by iCVD method using diethylaminoethyl methacrylate (DEAEMA) and vinylbenzyl chloride (VBC) monomers. Coatings were carried out at different DEAEMA and VBC monomer feed rates to the iCVD system. The chemical structure of the polymeric thin films were analysed by XPS and FT-IR, surface hydrophobicity by contact angle analysis, surface morphology and average surface roughness by AFM analysis, surface and polymeric mechanical properties by Tape Adhesion Test and optical microscope, bactericidal performance against gram negative E.Coli and gram positive S.Aureus bacteria by antibacterial activity test, and finally cytotoxic properties by cell viability test. It was observed that the adhesion strength of the surface increased with silanation processes and the polymeric mechanical strength increased with copolymerisation of DEAEMA and VBC monomers by iCVD method. The protonation of the surfaces as a result of plasma treatment with oxygen gas was proved by XPS analysis. Antibacterial polymers deposited on glass, fabric and PET substrates at a monomer feed ratio of DEAEMA:VBC/1:0.5 were found to have high antibacterial activity with an average log reduction of 5-6. Cytotoxicity studies of the coatings were carried out using the XTT procedure. According to the results obtained, it was observed that the copolymer film surfaces obtained have no cytotoxic effect against NIH/3T3 mammalian cells and have high antibacterial properties. In another study, polymers with high antibacterial properties were obtained by mimicking natural surfaces having high surface roughness and antibacterial properties. In order to examine the contribution of roughness to the antibacterial effect, the rough structure of the abrasive surface with two different average particle diameters, 36 μm and 8 μm, was transferred to polydimethylsiloxane (PDMS) polymer by soft lithography method. On these roughened surfaces, cross-linked antibacterial polymer was coated using DEAEMA and VBC monomers by iCVD method. The hydrophobicity of the surface was analysed by contact angle analysis, chemical structure by FT-IR spectroscopy, surface morphology and average surface roughness by AFM, and finally bacterial killing performance by antibacterial activity test. It was observed that the antibacterial activity against S.Aureus bacteria was higher than that against E.Coli bacteria in polymeric thin films coated on flat copy surfaces, while the antibacterial activity against E.Coli bacteria was higher than that against S.Aureus in polymeric films coated on roughened copy surfaces. When the antibacterial activity of the polymeric films coated on the flat surface, roughened copy surfaces were examined, it was observed that the highest antibacterial activity against S.Aureus and E.Coli bacteria was observed on surfaces with an average particle diameter of 36 μm (log reduction against S.Aureus bacteria was approximately 4.5, while it was approximately 7 against E.Coli bacteria). In another study, polymeric thin films with antibacterial properties were obtained by PECVD method using essential oils such as laurel, orange and rosemary. The chemical structure of the polymeric thin films deposited at 15 W, 30, 45 W and 60 W plasma powers were analysed by FT-IR, hydrophobicity of the surface was measured by contact angle analysis, surface morphology and average surface roughness were measured by AFM analysis, and bactericidal performance was measured by antibacterial activity test. It was observed that the polymeric thin films obtained with laurel oil, orange oil and rosemary oil showed different changes in contact angle values with increasing average roughness. In polymeric thin films obtained with laurel oil and rosemary oil, the contact angle value increased linearly with the increase in average roughness, while the opposite effect was observed in orange oil. In the antibacterial activity tests of polymeric thin films obtained with laurel oil, orange oil and rosemary oil, it was observed that the antibacterial mechanisms of action against S.Aureus and E.Coli bacteria were different. It was observed that 0.77 log reduction was obtained at 60 W plasma power against E.Coli bacteria in polymeric thin films obtained with laurel oil, 4.18 log reduction against E.Coli bacteria at 60 W plasma power in polymeric thin films obtained with orange oil, and 4.54 log reduction against E.Coli bacteria at 30 W plasma power in polymeric thin films obtained with rosemary oil. Within the scope of this thesis study, nature-inspired surfaces with high coating adhesion, abrasion resistance, hardness and high antibacterial properties were successfully formed on different surfaces using iCVD and PECVD methods. The obtained surfaces can be easily adapted to industrial production and can be used effectively in environments that threaten human health such as hospital-acquired infections, biomedical applications and medical devices can be used.