A Synthetic Approach to 'Smart' Microbial-Based Therapeutics and Population Regulators

Leopold Green, Ph.D.
Assistant Professor, Biomedical Engineering
Purdue University
Thu, March 03, 2022 at 2:00 PM

Current therapies for treating inflammatory bowel disease (IBD) and other chronic intestinal illnesses are effective in less than 30% of patients due to the lack of adherence to onerous prescription schedules and off-target effects. Synthetic biology offers a unique opportunity to engineer microbial drug delivery platforms that can significantly enhance drug safety and efficacy by overcoming current IBD treatment limitations. The engineered systems can colonize the gut and provide in situ surveillance by monitoring changes in the local environment. As an immunotherapy strategy, we aim to implement a synthetic circuit in probiotic E. coli strain Nissle 1917 capable of sensing chronic conditions and modulating host immune responses. Here, we adopt the previously characterized split activator AND logic gate to multiplex two input signals: the inflammatory biomarker tetrathionate and the IPTG inducer signal. We report 4 to 6-fold induction with a minimal leak when both stimuli are present. We also demonstrate the tunability of the logic-based genetic circuit by varying the ribosome binding site sequences. We are currently engineering the split activator to drive the expression of an anti-inflammatory effector. We will test if the engineered circuit can protect against intestinal inflammation in IBD mouse models in future work. Long-term, we will design strategies to sense the onset of chronic disease and engineer immune-modulating responses in microbial chassis.


Leopold Green, Ph.D.

Leopold N. Green, Ph.D., is an Assistant Professor in the Weldon School of Biomedical Engineering at Purdue University. Dr. Green’s current work involves engineering biological controllers in microbial systems as adaptable living therapeutics for chronic inflammation. Dr. Green received his bachelor’s degree in Chemistry from Hampton University in 2011. Dr. Green received the Ronald E. McNair Fellowship, the UNCF Merck Science Initiative fellowship, and The Hampton University 2011 Future Nobel Laureate award during his undergraduate studies. Dr. Green transitioned to the University of California, Riverside Department of Bioengineering for his doctoral studies. At UC Riverside, Dr. Green engineered nucleic acid-based nanostructures and coupled their mechanical properties to a synthetic transcriptional oscillator. Dr. Green received the Ford Fellowship Honorable Mention, the GAANN Graduate fellowship, and the NSF Graduate Research Fellowship. After completing his Ph.D. in 2017, Dr. Green joined Caltech as Postdoctoral Fellow, where he engineered population controllers in synthetic E. coli-based communities. Dr. Green is an NSF California Alliance for Graduate Education and the Professoriate Fellow, a 2020 Rising Star in Engineering in Medicine (Columbia University), and a 2021 Black Trailblazer in Engineering Fellow (Purdue University).