We hope our project may contribute to the iGEM community and help the future iGEM teams, we designed and constructed a small device for monitoring intestinal health based on butyrate microbial sensor. We also documented the parts and the construction of genetically engineered bacteria (Details in Biological experiments). Furthermore, we solved some difficulties in our experiments, and we hope our solutions may help for the future iGEM team.
In order to develop a small and quick-testing device with good sensitivity and specificity to monitor intestinal health, we designed the present device. The device includes the following modules: a determination chip, optical parts for excitation and reception of fluorescence wavelengths, a temperature control module, a display screen, a power supply, and a data input and output module. It is operated using a Raspberry Pi to perform a series of tasks.
The optic parts are the crucial parts that realize the function of the device. Within the optic parts, there is one light source and two optical filters. These optical filters provide the excitation wavelength (584 nm) and emission wavelength (607 nm), respectively. The mixture of genetically engineered bacteria and butyrate solution could emit fluorescence at 607 nm when excited by light of the wavelength 584 nm. Then the fluorescence could be captured and converted into electronic signals by the photoelectric sensors. After the construction of the device is done, we presented a testing process of the device. We recorded the correlation between the indications on the device and the intensity of butyrate in the form of a calibration curve, and within the range of 5.0–60 mM, the concentration of butyrate and signal linearity are well related. Data is eventually presented on the display-screen data processing module.
In our own project, the device is used to test butyrate level. Further, our methodology of this project could also be used to monitor other short-chain fatty acids (SCFAs), such as valerate and propionate (they paly important role in maintaining intestinal homeostasis). Therefore, the biological experiments and device integration in this project may also provide an inspiration for other teams to construct devices with similar functions.
For more specific information of the device, please move to the Experiment-hardware page or the hardware award page.
Hardware description page
Hardware awards page
In this project, we provided the new composite part with butyrate recognizing promoter, pchA gene, pLEE promoter and red fluorescent protein gene. The part link is following (click here to view). We utilized red fluorescent protein to reflect butyrate level. By doing so, we could be able to inspire other iGEM teams to use different fluorescent proteins (like green or yellow fluorescent protein) to determine other intestinal short-chain fatty acids (such as with valerate and propionate recognizing genes). Therefore, we might be able to utilize these different proteins to detect multiple SCFAs at the same time in the chip to comprehensively reflect intestinal health.
In order to optimize the sensitivity of the device, we concluded several factors that are needed to be noticed. The sensitivity depends on both the stability and the design of the device. To ensure the stability, we figured that the position of the determination chip should be strictly fixed. Besides, to ensure the vitality of the genetically engineered bacteria, the temperature should also be stable and is controlled at 37±0.1℃. High quality photoelectric sensors can ensure detection sensitivity.
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