The overall emphasis of this doctoral dissertation is on the design, synthesis, detailed characterization and application of amphiphilic hyperbranched fluoropolymers (HBFPs) crosslinked with poly(ethylene glycols) (PEGs) in complex polymer coatings as anti-biofouling surfaces. This dissertation bridges synthetic polymer chemistry, materials science and biology to produce functional coatings capable of fouling prevention, demonstrating thermo-controlled healing and acting as a benchmark surface to understand component:property relationships prior to increasing formulation complexities. A two-dimensional array of HBFP-PEG coatings was produced by the co-deposition of uniquely composed HBFPs with varying weight percentages of PEG. Bulk and surface properties were evaluated and assigned to formulation trends. Based on these findings, the most viable candidates were replicated and their fouling responses were assessed against three marine fouling organisms. An active mode of biofouling resistance was covalently grafted onto the surface of HBFP-PEG. The presentation of the settlement-deterrent molecule noradrenaline (NA) works in tandem with the highly-complex surface, to act as a dual-mode, anti-biofouling coating NA-HBFP-PEG. Secondary ion mass spectrometry (SIMS) was employed to quantify the extent of NA substitution. Biological assays against oyster hemocytes confirmed the activity of the grafted NA and cyprid settlement assays supported that the overall anti-biofouling ability of NA-HBFP-PEG was increased by 75%. Thermally-reversible crosslinks were installed as healable units throughout the framework of the networks, with the goal of generating coatings that could possess a greater resistance to mechanical failure. Small molecule and linear polymer models were probed by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) to demonstrate the controlled reversibility of the crosslinks. Optical microscopy was employed to visualize surface scratch healing and fluorescence microscopy was used to identify the adsorption behavior of fluorescently-labeled proteins. A benchmark, anti-biofouling surface was generated through thiol-ene crosslinking of a linear fluoropolymer with pendant alkenes (LFPene) with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). Core constituents were evaluated spectroscopically and surfaces of LFPene-PETMP, along with two model surfaces that largely expressed a single component, were analyzed to understand how individual elements and blending contributed to the physical, mechanical and anti-biofouling properties to generate a performance baseline to compare against future generations.

Lubricant-infused surfaces (LIS) are created by modifying chemical and physical properties of surfaces with aim of lowering surfaces energy where designed surface will possess liquid-repelling behaviors under low tilting angles. LIS has great potential to be applied on implantable devices due to it is stable anti-biofouling properties under fluidic environment. However, a few studies have reported that the existing research on implant surface uses complicated methods and high cost fabrication to create LIS on titanium implants. Furthermore, current limitation of LIS coatings for titanium implants lies in the lack of tissue integration and cell interaction. As a result, LIS prevents both bacteria and bone cells from adhering to the interface between implant and natural bone. This unselective blocking is problematic for titanium implants used in orthopaedic surgery when devices are required to possess tissue integration properties to facilitate long term fixation in the human body. The overall objective of this thesis is to apply LIS on titanium surfaces via a chemical modification technique and simultaneously integrate bio-functional features onto LIS to promote osteoblasts adhesion. In this project, chitosan and collagen were used to facilitate cell adhesion. To start with, three methods were used to immobilize chitosan on titanium to obtain the desired bio-functional LIS coatings: (1) LIS on top of (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) crosslinked chitosan; (2) LIS on dip-coated chitosan; (3) LIS generated from GPTMS and Trichloro(1H,1H,2H,2H-perfluorooctyl) silane (TPFS) mixed silanes modified titanium surface followed by chitosan functionalization. Among these modification techniques, method (3) showed optimal anti-biofouling and osseointegration properties. Since collagen is well known for increase of cell interactions, it was used via mixed silanes functionalization method. Finally, the properties were compared with chitosan coated surfaces. During tests, surface wettability was measured, anti-biofouling properties and osseointegration was examined with staphylococcus aureus and SAOS-2 cells, respectively. We found that chitosan modified surfaces using method (3) not only significantly increased cell adhesion in comparison with the other two modification methods, but also dramatically decreased bacterial adhesion compared to collagen coated LIS on titanium. Although collagen has better cell adhesion properties than chitosan, collagen coated surface significantly decreased antibiofouling properties. In conclusion, bio-functional lubricant-infused titanium surfaces created by chemical vapor deposition (CVD) method with mixed silanes is a feasible and straightforward method to immobilize biomaterials and stabilize the lubricant layer on titanium substrates. Chitosan coated LIS on titanium prevents bacterial adhesion and simultaneously promotes targeted cell binding. / Thesis / Master of Applied Science (MASc) / Biofouling is a major issue in implantable titanium devices such as coronary stents, plates and nails, and formation of biofilm on implants can lead to infection and failure of the device. Biofilms formed by bacterial adhesion could be resistant to antibiotics and can provoke a series of inflammatory response. Recent advances in anti-biofouling surface treatment has resulted in designing supper slippery lubricant-infused omniphobic surfaces which are inspired from the Nepenthes pitcher plant. Liquid which is tethered on the surface offers a stable liquid interface, repelling both aqueous and organic liquids meanwhile showing excellent bacteria repellency. Lubricant-infused surfaces (LIS) are resistant towards biofilm formation and produce a stable surface that prevent non-specific adhesion. As a result of this repellent properties, LIS also repels the adhesion of desired biomolecules and cells such as osteoblasts, bone cells and growth factors which are essential factors for bone recovery at the implant-bone interface. Our motivation in this thesis is to create a lubricant-infused coating on titanium surfaces that possesses both bio-functional and blocking features. We designed surfaces that decrease implant infection caused by non-specific adhesion and simultaneously promote targeted binding of biomolecules and cells that will increase osseointegration of the implant to enable long-term fixation.

Biofouling is a major issue in applying nanofiltration and reverse osmosis technologies for wastewater treatment. Biofilm formed on the surface of membranes will severely decline the flux and cause energy waste. In this study, a novel biofouling control method that applies D-amino acids to inhibit biofilm formation was investigated. The D-amino acids previously reported to inhibit biofilm formation and disrupt existing biofilm – D-tyrosine and the mixture of D-tyrosine, D-tryptophan, D-leucine and D-methionine were tested. Pseudomonas aeruginosa and Bacillus subtilis were used as model Gram-negative and Gram-positive bacteria, respectively. D-amino acids have little effect and some effect on inhibition of biofilm formation and disruption of exiting biofilm to Pseudomonas aeruginosa, but have good effect to Bacillus subtilis. A commonly used microtiter plate assay for quantitative biofilm measurement was systematically evaluated and optimized for screening biofilm control agents. The effect of D-tyrosine on inhibition of organic fouling and P. aeruginosa biofouling on NF90 membrane surface in bench scale dead end filtration experiment was examined, which shows that D-tyrosine can effectively inhibit organic fouling and P. aeruginosa biofouling on NF90 membrane surface.

The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication of hybrid membranes in existing facilities. In the CIPS process, a first step forms the thin metal-rich selective layer of the membrane, and a succeeding step the porous support. Precipitation of the selective layer takes place in the same solvent used to dissolve the polymer and is induced by a small concentration of metal ions. These ions form metal-coordination-based crosslinks leading to the formation of a solid skin floating on top of the liquid polymer film. A subsequent precipitation in a nonsolvent bath leads to the formation of the porous support structure. Forming the dense layer and porous support by different mechanisms while maintaining the simplicity of a phase inversion process, results in unprecedented control over the final structure of the membrane. The thickness and morphology of the dense layer as well as the porosity of the support can be controlled over a wide range by manipulating simple process parameters. CIPS facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. The nature of the CIPS process facilitates a precise loading of a high concentration of metal ions that are located in only the top layer of the membrane. Moreover, these metal ions can be converted—during the membrane fabrication process—to nanoparticles or crystals. This simple method opens up fascinating possibilities for the fabrication of metal-rich polymeric membranes with a new set of properties. This dissertation describes the process in depth and explores promising applications: (i) catalytic membranes containing palladium nanoparticles (PdNPs), (ii) antibiofouling tight-UF membranes containing silver chloride (AgCl) crystals, and (iii) palladiumrich PBI hollow fibers for H2 recovery.