Our project intends to design a synthetic gene circuit that reports chronic stress levels by sensing glucocorticoid levels. In our results page(see results page for more details) , we have demonstrated a promising prototype that generates a colorimetric signal upon glucocorticoid stimulation, allowing us to discuss our circuit's possible application further. In general, we plan to deliver our glucocorticoid-detecting circuit subcutaneously to generate visible or detectable signals under high-stress exposure. We’ve considered two possible approaches to deploying our circuit in a real-world scenario: implantation of pre-engineered cells or engineering somatic cells with virus vectors. The pros and cons of these strategies and the inputs directly from our potential users are also discussed on this page.
Here we hope to come up with solutions against the increasing mental stress in academia. Naturally, we consider grad students and young scientists our major potential users. By interviewing some Ph.D. students (see HP overview-interview page for more details) , we noticed that their major concerns regarding a cell-based stress reporting device are related to safety and flexibility. Some students also raised some privacy concerns.
Beyond the scientific community, the phychologists we interviewed also inspired us that our project may also help psysicians monitor their patients' mental conditions(see HP overview-interview page for more details) . She mentioned that the output signal should be easily detectable by physicians only instead of panicking the patient with visible signals.
（1）Circuit delivery
We plan to deliver our circuit subcutaneously to generate a localized “tattoo” like pattern. This delivery can be achieved by either virus, which engineers somatic cells directly, or by injecting encapsulated engineered cells. And the following figure shows the specific working principle of these two methods.
Figure 1 The working principle of implantation of encapsulated engineered cells and recombinant adeno-associated virus cells.
Direct injection of encapsulated engineered cells is another widely-used approach to deliver synthetic gene circuits for therapeutic or diagnostic purposes. It has been reported that encapsulated designer cells can maintain functionality for months. Compared to the virus-based approaches, direct injection of encapsulated cells allows the pre-selection and testing of the engineered cells before actual injection, ensuring the robustness and effectiveness of the implant. However, the long-term survival of these designer cells and the potential inflammation raised by the encapsulated implant remains problematic.
As we’ve discussed in our future work , we plan to try both approaches in vitro and hopefully get IACUC approval to try them in mice to identify a better choice for our future application.
（2）Signal output
Our results page demonstrated a Tyrosinase-based approach to generate colorimetric signals: the designer cell turns black upon glucocorticoid stimulation (see results page for more details). However, according to our interview with potential users, this simple approach may not meet their visual appearance or privacy requirements. One possible solution would be integrating the stress-sensing tattoo with an existing classical tattoo, which would require colorful output signals. Hence, we plan to perform directed evolution on known chromoproteins to improve their performance in mammalian cells. Another approach would be fluorescent proteins that only generate signals under specific excitation. We have tested tdTomato in our in vitro experiments (see results page for more details), but further studies are still required to determine whether fluorescent signals can be detected under the skin.