Design and Application of Surfaces for Biological Fouling Control

Abstract

Undesired biological fouling on surfaces causes significant burdens to industry, the environment, and society. For example, surfaces contaminated with bacteria and viruses contribute to disease transmission; blood-contacting medical devices are susceptible to thrombus formation, which can lead to embolisms and death; and biofouling on ships results in increased fuel usage, cost, and carbon dioxide emissions. Biological foulants have a wide range of modulus and scale and include proteins, cells, micro-organisms, and macro-organisms. The diversity of biological foulants makes preventing fouling difficult and often necessitates costly and frequent cleaning. This dissertation presents the development and application of a new system of durable antimicrobial surfaces that prevent biological fouling due to the incorporation of secondary metabolites, which are compounds produced by plants for various purposes, including defense against bacteria, fungi, and viruses. A first-of-its-kind surface capable maintain of rapid disinfection rates over several months was developed by incorporating select plant secondary metabolites with high antimicrobial efficacy, such as alpha terpineol and cinnamaldehyde, into a polyurethane matrix. The surfaces achieve 99.99% disinfection of E. coli, MRSA, and P. aeruginosa within 5 minutes and the SARS-CoV-2 virus within 30 minutes. They also remain effective under significant environmental stressors, such as freezing, abrasion, and ultraviolet light exposure. The utility of the antimicrobial surfaces is further explored in two practical applications: marine biofouling and antimicrobial wound dressings. In addition to pathogenic organisms, the antimicrobial surfaces are highly effective at preventing the marine bacterium C. lytica and the microalgae N. incerta and C. vulgaris from attaching and forming biofilms. Furthermore, compared to the commercial gold standard foul release coatings Intersleek 700, 900, and 100SR, the antimicrobial coatings had lower or comparable biomass remaining after 10 psi and 20 psi water jet removal. For the antimicrobial wound dressing application, the polyurethane system used previously was replaced with the medical-grade polyurethane system Baymedix®, and the coating remained effective at killing E. coli, MRSA, and P. aeruginosa, demonstrating the system’s adaptability for different uses. An infected porcine burn wound model showed that the antimicrobial-coated gauze wound dressings significantly decreased the bacterial burden when changed daily compared to wounds treated with bacitracin and did not hinder or interfere with the wound healing process. These two real-world applications showcase the antimicrobial surfaces' versatility. Finally, the addition of hydroxy terminated poly(dimethyl siloxane) (PDMS-OH) to the polyurethane matrix to create a passive antifouling surface for blood contacting devices is explored. Due to the PDMS’ low glass transition temperature, the surface has enhanced interfacial mobility allowing it to prevent adsorption of cells and other thrombus elements. This PDMS-OH PU surface significantly reduces the adhesion of platelets, peripheral blood mononuclear cells, polymorphonuclear neutrophils, neutrophil extracellular traps, and bacteria. Additionally, the PDMS-OH PU surface did not cause significant platelet activation compared to control surfaces. In summary, the antimicrobial coatings are extremely effective at preventing biological fouling in a diverse range of applications. The antimicrobial compounds can be varied to optimize the coatings to target specific fouling organisms, and it can be applied to a variety of substrates using commercial coating methods such as spray coating and brush coating.