Development and characterization of chitosan coatings by plasma-grafting for antibacterial surfaces
|Authors:||Miguel Vaz, Juliana|
|Abstract:||The risk of bacterial colonization on abiotic surfaces poses important challenges in various fields of science. In this scenario, antibacterial coatings were developed, using a large number of materials. The surface modification of polymeric materials allows to improve surface properties, facilitating the development of optimized materials with biological responses adapted or adaptable to the environment in which they will be implanted. Chitosan is a biopolymer with inherent antimicrobial activity which can be used in a wide variety of health care and industrial applications, making it particularly interesting for the development and application of novel functionalized materials, i.e. antibacterial properties. In this study, different types of chitosan were characterized according to their degree of deacetylation (DDA) and molecular weight (Mw), using Nuclear Magnetic Resonance (¹³C NMR) and Size Exclusion Chromatography (SEC), among others. The results obtained through these analyses revealed the great importance of the characterization of biopolymers since their properties can vary according to the production methods, which can influence its use as an application. Afterward, the methodology applied for the treatment and modification of surfaces using plasma, for the surface functionalization and grafting of molecules was validated. Initially, PTFE (poly(tetrafluoroethylene)) films were used to verify the efficiency of the proposed methodology for the treatment and surface modification. Three spacer molecules glutaric anhydride (GA), poly (ethylene glycol) bis (carboxymethyl) (PEGb) and poly (ethylene-alt-maleic anhydride) (PA), with different characteristics were used to covalently attach the chitosan coating to the aminated PTFE surfaces. Each step of the surface treatment was verified by X-ray Photoelectron Spectroscopy (XPS), through changes in chemical composition, by contact angle measurements and by colorimetry. The topographic and roughness changes after grafting were also observed by Scanning Electron Microscopy (SEM) and profilometry. These results demonstrated that the type of anchors has a greater influence on the coating process than the molecular weight of the different types of chitosan. To verify the antibacterial response of the different types of coatings obtained, tests were initially carried out using Xylella fastidiosa and revealed the potentiality of the substrates covered with chitosan. Tests using pathogenic bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were performed confirming the antibacterial behavior of PTFE-plasma-PA-CHIMW samples. These results encouraged the application of this methodology in PET (polyethylene terephthalate) substrate, a polymer widely used in the field of conventional textiles as well as in the production of hospital textiles and biomaterials. Thus, the plasma-grafting methodology developed in this study, for the production of chitosan coatings, can be applied to the production of surfaces where antibacterial activity is desired.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||24 April 2018|
|Collection:||Thèses et mémoires|
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