Developing a steady state growth model for epithelial cancer cells and biocontained E.coli DEP cells.

• Vishal Somasundaram, Chemical Engineering, University of Delaware

• Priyanka Nain, Department of Chemical and Biomolecular Engineering, University of Delaware
• Aditya Kunjapur, Department of Chemical and Biomolecular Engineering, University of Delaware

Emerging research indicates that microbial interactions play a pivotal role in the success of in vivo studies leading to cancer treatments. The interaction between bacteria and mammalian cells is complex and not yet fully characterized. However, Kunjapur et al. have developed in vitro methods to verify bacterial containment when in contact with mammalian cell cultures. This study aims to further the development of a stable coculturing environment in which bacterial and mammalian cells can coexist. For our investigations, we selected the A549 cell line due to its robust growth characteristics in laboratory conditions and its heightened sensitivity to an array of oncological interventions, making it an invaluable model for subsequent in vivo explorations. In conjunction, we are utilizing an engineered Escherichia coli strain, DEP, a synthetic auxotroph characterized by its dependency on a nonstandard amino acid, biphenylalanine (bipA). This synthetic auxotroph displays significant promise for its potential role as a biosensor or as a therapeutic host in disease models. Coculture techniques were used to assess bacterial escape and proliferation within mammalian monolayers. Using fluorescence microscopy and selective plating, we demonstrated no viable extracellular bacteria up to 72 hours following infection of A549 cells with DEP cells. The infected mammalian cells showed no morphological abnormalities in nonpermissive conditions, while in a permissive state, steady state coculture work is still being pursued. Additionally, we have developed a predictive model based on the Monod growth kinetics to characterize the growth dynamics of DEP in the presence of bipA. The model drew upon various assays that tested factors such as substrate presence, inoculum density, and media composition to replicate in vitro conditions accurately. Such a model helps understand cell behavior under varying conditions but also aids in optimizing coculturing environments for potential therapeutic interventions.