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Functional Multilayer Films

Final Report Summary - FUNCMLFS (Functional Multilayer Films)

Layer-by-layer self-assembly technique is a powerful route to functionalize surfaces and/or prepare polymer platforms for controlled release of biological molecules from surfaces. This technique is based on alternating deposition of interacting species at the surface. A wide range of synthetic polymers, self-assembled polymeric nanostructures (polymer micelles), metal nanoparticles, viruses, liposomes, natural polymers (e.g. DNA, RNA, proteins, peptides etc.) and many other functional molecules can be self-assembled at the surface due to versatility of polymer interactions, e.g. covalent bonding, electrostatic, hydrogen bonding, hydrophobic, π-π stacking, charge-transfer, bio-specific, metal-ligand interactions. The simplicity, low cost and the use of aqueous polymer solutions have made this technique attractive especially for biomedical applications.
The overall objective of this project was to introduce functionality to polymer multilayer films and generate the fundamental knowledge on structure-property relationship in LbL films. In particular, we aimed to understand intermolecular interactions at surfaces, effects of physicochemical parameters on LbL assembly/post-assembly and controlled release of film components/functional molecules from surfaces. In particular, we have extensively investigated the incorporation of block copolymer micelles with pH-responsive polybasic cores and temperature-responsive coronae into layer-by-layer films and the effect of pH and temperature on the release of functional molecules from the surface. Such micelles were stable at physiological pH, however disintegrated with decreasing pH, releasing the biological molecules encapsulated in the micellar cores. We have also demonstrated that temperature-induced conformational changes of coronal chains around the lower critical solution temperature or upper critical solution temperature of the coronal block increased the amount of functional molecules released from the micellar cores at a certain pH. The response of such block copolymer micelles in moderately acidic environments is specifically important and promising due to the acidic nature of tumor tissues and local pH drops in the body induced by infection. For example, we have shown in one of our studies that mono- and multi-layer films of block copolymer micelles with zwitterionic coronae and polybasic pH responsive cores could impart dual functionality to a surface, i.e. bacterial anti-adhesive and anti-bacterial properties. Zwitterionic coronal blocks which reside both positive and negative charges in the same repeating unit assured the bacterial anti-adhesive properties of the coating, whereas the polybasic micellar cores assured the pH-induced release of the anti-bacterial agent at moderately acidic conditions. Considering the signifiant number of patients affected by hospital-acquired infections every year and the total annual cost that hospital-acquired infections cause all over the world, these results are promising for future biomedical applications, e.g. coating medical implants/devices.
The publications produced throughout this project specifically contributed to understanding the effect of pH and temperature on the physicochemical properties of the multilayer films. Fundamental knowledge generated from this project may serve as a basis for the development of more advanced coatings for biological applications.