Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Antimicrobial Peptide Adsorption and Storage on Oxidized Metal Surfaces to Mitigate Bacterial Attachment" By Jesus Hector Morales Espejo Purdue MSE Ph.D. Final Exam Advisor: Professor David F. Bahr ABSTRACT Food safety has become an important issue globally due to increasing foodborne diseases and changes in food habits. The occurrence of illness due to consumption of foods contaminated by bacteria has a great impact on public health worldwide. Only during June 2018, the Center for Disease Control has reported 160 hospitalizations and 5 deaths in USA as a result of foodborne diseases. Although some food products can come contaminated from the farm, it has been demonstrated that in most cases the food gets contaminated in the food processing plant or in food retailers when in contact with contaminated surfaces like slicers, conveyors, knives, carts, blades, etc. In an effort to mitigate this problem, the present work aims to design an antibacterial surface by combining the use of an antimicrobial agent and surface modification. Pulsed laser oxidation was used to form oxide layers on Ti-6Al-4V and 304L stainless steel under atmospheric conditions. Analysis of cross sections revealed that these artificially created colored oxide layers vary in thickness and exhibit cracks which penetrate between 1 - 6 μm into the substrate. These fine surface cracks have been used as a reservoir for storing nisin, an antimicrobial peptide with high activity against a broad spectrum of Gram-positive bacteria. The antibacterial efficacy against Listeria monocytogenes and the response of the surface to mechanical impact were evaluated, confirming that nisin remains in the layer and still displays good antibacterial activity. Release kinetics tests demonstrated that nisin is desorbed from the cracks only when the oxide layer is submitted to acidic pH, and sustained washing and wear does not remove the nisin. This suggests nisin-infused microcracked surfaces are viable for creating antibacterial food-contact surfaces, preventing the spread of foodborne pathogens. Date: Wednesday, July 25, 2018 Time: 1:00 P.M. Place: ARMS B071