With programmable cell sensing/response pathways system, BioWatcher cells can be engineered to sense user-specified ligands by simply swapping the nanobodies and applying different downstream gene expressions. In turn, the BioWatcher system can elicit custom responses accordingly. In our experiments, we used the most well-studied nanobodies, GBP, on our sensing module and mCherry and Lux gene as the output signal to prove that the system is working. Interestingly, we designed cutting sites on the sensing module for the purpose of swapping different kinds of nanobodies to detect different soluble ligands and biomarkers. As different nanobodies and downstream gene expression are coupled and applied in the BioWatcher system, this programmable system becomes very versatile and user-oriented. Therefore, BioWatcher is a system with great potential for any application.
According to the information from iCAN database (Institute collection and Analysis of Nanobody), over two thousand kinds of nanobodies are available for recognizing different antigens including molecular-bound molecules and soluble molecules. Therefore, by adjusting the nanobodies, BioWatcher system can adapt to detect toxins, heavy metal ions, pollutions…etc, in the extracellular environments including but not limited to human circulating system. The output signal in this system is also interchangeable. By using different downstream gene expression in the gene circuit, the reporter cells can be operated for therapeutic purpose, drug delivery, cell killing signals, just to name a few.
For example, we can change the detector to toxin-specific nanobodies and deliver the cell into zebrafish. By putting the BioWatcher zebrafish into rivers and ponds, we can tell that the water is polluted when BioWatcher zebrafish is turning red or green depending on the chosen output. This approach can be very useful in poor regions that can’t afford expensive chemical testing to prevent the people from harm and greatly promoter the health of the people living in the regions.
So far, 2391 kinds of nanobodies and countless downstream genes are available for use. The combinations are innumerable for various purpose and usage. The biggest limitation of this system is, probably, our own imagination!