Bio-inspired aryldiazonium cabrohydrate coatings; synthesis, suface modification and applications in biofilm control

This thesis examines the use of aryldiazonium surface modification strategies in order to produce surfaces terminated with saccharide functionality with applications in controlling surface bound biofilm progression. To this end a brief introduction into historical methods of surface glycosylation are provided with an overview on aryldiazonium grafting techniques, rapid mild and efficient methods of covalent surface modification. The processes of biofouling progression are considered in both marine and in-vivo environments with discussion on anti-fouling strategies employed in the available scientific literature. The synthetic processes involved in the production of lactoside based aminophenol, and ?-cyclodextrin conjugated aminophenol, diazonium precursor\u27s materials are provided. To test the effect of functionalisation methodology on the resulting surface coating properties, aryldiazonium grafting is performed on carbon substrates modifying them with lactoside functionality using two methods of aryldiazonium grafting, electrochemical reduction and spontaneous nucleophilic attack at the surface. Surfaces were characterised by a range of spectroscopic methods, sessile drop water contact angle analysis, and protein retention experiments. Significant differences were found in film properties between the two methods with electrografting displaying characteristics indicative of a more complete coating layer. These coatings were found to specifically bind lectins, increase surface wettability and to enhance non-specific protein rejection capabilities of the surface. Also reported is the surface modification of non-conductive surfaces (polyamide, stainless steel and PES) with lactose functionality by spontaneous aryldiazonium grafting. For both polyamide and stainless steel samples, pre-treatment steps which introduce surface hydroxyl group functionalities were found to facilitate surface modification by spontaneous aryldiazonium grafting. PES required no such pre-treatment. Similar characterisations to those applied on the carbon surfaces were also performed on these materials where applicable. The biofilm rejection properties of these lactose coated materials were investigated by immersion in coastal waters over a heavy fouling season. Retained biomass was quantified by a combination of spectroscopy, opacity, microscopy and ATP analysis. In all instances, following a light rinsing protocol to remove unbound biomaterials, lactose coated materials displayed lowered degrees of biomass retention. Aminophenol tailed β-Cyclodextrin compounds were observed to form supramolecular self-assemblies by head to tail cavity inclusions. This behaviour was found to render the compound inactive under standard aqueous aryldiazonium salt forming conditions. The crystals obtained were characterised by X-ray crystallographic methods in addition to DLS analysis and NMR spectroscopy studies. Suitable disaggregating conditions were developed and carbon, polymer and stainless steel surfaces were modified via spontaneous aryldiazonium grafting to produce cyclodextrin coated materials which displayed enhanced protein rejection capabilities. Additionally, glassy carbon electrodes modified by these methods were found to retain their host-guest cavity capabilities and were employed in the sensing of a cavity bound ferrocene redox probe. From these studies, surface coverages were found to approach close packing density with monolayer coverage confirmed by AFM scratching experiments. In summary, aryldiazonium surface grafting was used to produce saccharide modified surfaces with enhanced protein rejection capabilities that may have potential in sensing applications