There are products (such as polymer based gels) that rapidly stops blood loss However, they require physical application to the wound, meaning that they would not be able to stop internal bleeding and would not be practical to chronic or potentially-widespread bleeding such as hemophilia. Our cells would receive either a physical or chemical signal in response to a blood vessel being broken changing the extracellular pressure or releasing tissue factors through the extrinsic coagulation pathway, respectively. This would either induce a promoter, resulting in either a positive transcription loop or activation of an allosteric modulatory switch. The circuit would output cofactor 10a (FXa), the catalyst for the coagulation pathway. The system would be tested in cell culture and murine models. Tissue Factor is released by the ruptured walls 1 Factor 10a (Xa) molecule can catalyze the formation of 1000 thrombin molecules

Many physiologists and neuroscientists use optical methods to measure cell behavior 1)multiple portions of the sample could be monitored simultaneously, representing interactions between different cell species with different cellular functions 2)measurements can be made real-time 3)measurements can be relatively non-invasive. Current methods involve extrinsic dyes or proteins that can cause photodynamic damage to the cells. Our pathway would receive a (neuro)chemical signal from a neighboring cell which would set off a signaling cascade that ultimately excites a fluorescent protein. CRISPR? The half life would have to be short and the circuit regulation cascading because both are fast and transient enough to allow for the next excitation by the next action potential. https://www.wired.com/2014/07/neuron-zebrafish-movie/