SUMMARY

This work begins with chemotaxis studies involving Salmonella typhimurium. Known chemical attractants such as ribose, serine, and aspartic acid were tested in capillary tube setups, as well as chemical repellents, such as nickel and sodium acetate. It was found that high concentrations of both attractant and repellent, approximately 10% chemical in deionized (DI) water, yielded better separation results than lower concentrations, such as 1% and .1% chemical in DI water. Utilizing these attractants or repellents appropriately can allow live bacteria to be directed in a desired manner in a microfluidic device, while dead bacteria, which yield no response, can be separated into a waste reservoir. This study also introduces a method of capturing Salmonella typhimurium through the use of magnetic nanoparticles without functionalizing them with antibody or amine coatings. Based on the work by Deng et al., MNPs were prepared in various ways to alter their diameter and surface characteristics to achieve optimal capture efficiency. In addition, different polymer coatings were tested, such as poly lysine, chitosan, polyethylenimine (PEI), and dendrimer. Scanning electron microscopy (SEM) was used to image nanoparticles and bacteria. A capture efficiency of approximately 90% has been achieved through the use of a poly lysine coating on the MNPs. A macro-scale flow cell prototype will be designed and characterized in order to introduce the MNPs to the bacteria, mix them thoroughly, and then, through the use of a magnetic field, separate the bacteria-MNP aggregates from the bulk fluid. Finally, intervention of bacteria is a significant topic in food safety applications. This study utilizes Fe III to inhibit bacteria growth. This chemical was used in the presence of Salmonella, E. coli, and Pseudomonas. Further experiments were conducted with raw chicken and lettuce contaminated with Salmonella typhimurium.