Tissue culture contamination for fun and profit – Novel in vivo biosensors for on-line monitoring of mammalian cell cultures

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Lisa Goers, J. Krishnan, Cleo Kontoravdi, David Stuckey, Paul Freemont, Karen Polizzi

Imperial College London, United Kingdom

Mammalian cell cultures are used for production of biopharmaceuticals, e.g. monoclonal antibodies. Only mammalian hybridoma cells contain the pathways for antibody production, but due to their multicellular origin the cells have complex nutrient requirements. Cell growth and antibody production is limited by supply of essential nutrients such as glutamine and accumulation of toxic waste products such as lactate. Many attempts have been made at tackling these challenges, e.g. by optimising growth media to keep metabolite concentrations at optimal levels. These approaches have been hampered by our ability to monitor relevant cell culture parameters such as metabolite concentration dynamics in real time. The aim of this study is to develop a solution to this problem using a Synthetic Biology approach. Whole-cell bacterial biosensors for important culture parameters, such as glutamine and lactate were designed, built and characterised. The biosensors were designed by applying the principles of standardisation and modularisation to natural metabolite-sensing systems. Characterisation of the biosensors in isolation is followed by validation using cell culture samples and co-culture with hybridoma cells allowing on-line monitoring. Our biosensors are also more generally applicable in any experimental context that requires sensing of metabolites. The results of this study also highlight the many challenges of applying synthetic biology constructs to complex industrial contexts. Finally, these whole-cell bacterial biosensors have great potential. By linking the detection step to a transcriptional output, the bacterial cells could directly respond to the information by changing culture conditions. This could lead to a low-cost artificial symbiosis system.