Liu, Shuhao (2022-10). Development and Characterization of Functional Surfaces and Coatings with Microorganism Repellent and Inactivity Properties for Enhanced Hygiene and Safety. Doctoral Dissertation.
Thesis
Microorganism, especially pathogenic bacterium, creates considerable problems and challenges for individuals and society. Large numbers of humans get bacterial infections, and enormous economic burdens are spent annually on countries worldwide. There is an increasing need for the desired surface and coating techniques to reduce and eliminate bacterial contamination and cross-contamination. The bacterial repelling method has been an intriguing way to gain increasing attention over the past twenty years. The superhydrophobic surfaces with pathogens' repellency capability without biocides attracted more attention. Superhydrophobic surfaces required synergetic effects by nanotexture and reduced surface tension. Advanced techniques, including photolithography and reactive-ion etching, can be applied to construct the patterned nano-texture. And layer-by-layer, chemical vapor deposition, and chemical etching can be used to produce durable random nanotexture. However, these techniques are not cost-effective and large-scale productive for applications in food, agriculture, and essential healthcare, requiring large practical areas, considerable amounts, and cheap products. Superhydrophobic surfaces produced by large-scale and easy prepared methods by silica and diamond nanoparticles submerging deposition and short-time chemical solution modification of nanoparticles were prepared in this work. Both silica and diamond nanoparticles are successfully used in the studies to provide desired surface nanotexture and are followed by a fluorinated modification to reduce the surface tension. The superhydrophobic coating surfaces display reductions higher than 99.5% in bacterial adhesion against food- and healthcare-related bacterial cells. Two types of nanoparticles showed good mechanical durability that can be anticipated to work in harsh environments. Safety of the biocide is one of the concerns used in food and healthcare contact surfaces. Lysozyme is a natural protein that inactivates the bacteria by two mechanisms: 1) hydrolysis of peptides on the cell wall and 2) physically attacking the cell membrane due to the electrostatic interaction. Synergetic effects of superhydrophobicity and immobilized lysozyme on the coating lead to superior bacterial prevention of ~99.99% and 99.9999% reduction against gram-negative and gram-positive healthcare pathogens. The novel dual-functional coating with the higher effects on bacteria because of the synergy makes it an attractive candidate for application on food and healthcare contact surfaces.
