Surface Grafted Polymer Brushes: A Versatile Platform for Antibacterial Applications

Various strategies have been proposed and applied to prepare antibacterial materials able to respond to different requirements specific for antibacterial applications. Among diverse strategies the approach based on substrates modification with polymer brushes proved both versatile and reliable. Polymer brushes are thin polymeric films with all chains tethered with one end on a surface and since the development of SI-ATRP they can be obtained with good control over conformation, architecture and thickness. Therefore polymer brush coatings can be tailored with desired and fine tuned properties as functional biomaterials for a large variety of biomedical applications. The main objective of this Thesis was to develop versatile platforms for antibacterial applications based on polymer brush surfaces able to prevent bacteria adhesion and/or to kill bacteria on contact or through bacteria triggered controlled release of an antimicrobial compound. Moreover, novel systems based on polymer brushes have been synthesized as hydrolytically degradable platforms for potential biomedical applications. Chapter 1 analyses the mechanism of the biofilm formation and different strategies developed to inhibit bacterial adhesion, to prevent biofilm formation and proliferation and to reduce hospital-acquired bacterial infection. Various approaches for surfaces modification with polymer brushes are discussed, emphasizing on the possibilities of tailoring their antibacterial properties. Chapter 2 explores, for the first time, S. Epidermidis adhesion on PHEMA or POEGMA brushes on a wide range of grafting densities and film thicknesses. Both brushes carry functional groups on each repeating unit and are more appropriate for the development of platforms for novel biomedical applications. In Chapter 3 the possibility to obtain dual functional coatings combining the bacteria repellent character of the polymer brush with the possibility to selectively immobilize antibiotics is investigated. The antibacterial activity against S. Epidermidis of vancomycin modified surfaces is analyzed as a function of polymer brush structure and functional group used for coupling of the antibiotic. The aim of Chapter 4 is to develop systems based on polymer brush able to release an active compound in the presence of selected bacterial signals. A dye is coupled to PHEMA brushes via a specific linker sensitive to autolysins or beta-lactamase and its controlled release is monitored as a function of brush architecture. Finally, Chapter 5 focuses on improving existing hydrolytically degradable polymer brushes by neighboring group participation of a catalytic moiety. Moreover, the possibility to develop novel hydrolytically degradable polymer brushes based on polyphosphoesters is reported. The two studied systems are suitable as building blocks for platforms with antibacterial applications.

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