Team:SHSBNU China/Hardware

• Acknowledgement
• Team
  Team Members Our School Collaborations Attributions
• Judging
  Judging Achievements
• Model
  Modeling Software
• Safety
• Human Practices
  Intergrated Human Practices Public Engagement
• Parts
  Overview Basic parts Composite Part Collection Improve
• Lab
  Experiments Notebook Protocols
• Project
  Inspiration Description Design Results Hardware Demonstrate Prospect

Hardware

In the 2017 design (https://2017.igem.org/Team:SHSBNU_China/Demonstrate), we plan to let patients eat probiotics (E.coli Nissle 1917) with ThsS/R plasmids directly. But this approach can still have certain biological safety risks.

To make detection safer and reduce the risk of bacteria entering the gastrointestinal tract, we decided to design a semi-permeable membrane detected capsule in which patients swallow capsules, where bacteria perceive intestinal inflammatory molecules and respond biologically accordingly.

From our HP, we got that:
① The time the capsule stays in the digestive tract can be long or short.
② It is best for the capsule to stay in the suspected area for a longer period of time to fully contact the biosignal.
③ The design of the capsule needs to consider the convenience of recycling.

We also thought of that the capsule must:
1. be structurally strengthened, not easy to crack
2. keep the molecules of the digestive enzyme out of it
3. constrain the bacteria within it
4. allow small molecules to pass through, enabling them to be perceived by bacteria
5. be easy to retrieve after leaving the digestive tract
6. have no electronic components, reducing cost and increasing the safety
7. be moderate in size and easy to swallow

Based on the ideas above, we designed a capsule, which is shown below

Capsule Design

The lower half of the capsule consists of a liquid medium, a shell, and 3 semi-permeable membrane windows.
Bacterial pellet and liquid media are separated by sealant
Considering the strength of the capsule, the semi-permeable membrane is designed with a window instead of the entire capsule
The upper part of the capsule is made up of a cylinder (allowing a magnet to move in a fixed direction)
Thrust magnet (to be pushed by MagKey, in order to press the Pushing rod to break the seal)
Metal sheet (made of ferromagnetic material which attract the Thrust magnet and hold it in place)
Bacterial pellet
Water-proof seal

Start Capsule by using magnetic key MagKey (push the Thrust magnet with reverse magnetism, to break the water proof seal)
[Using capsule]
① take out the capsule from package.
② Using the MagKey push the thrust magnet, the pushrod presses down and break the seal and the bacterial pellet fall into the culture medium.
③ Bacterial pellet is dissolved and bacteria start to grow.
④ Tear off the semi-permeable seal, so that the semi-permeable membrane can be exposed, then eat the capsule.

When the capsule enters the intestine, use magnets to attract capsule, control capsule positioning, and keep the capsule in a specific position.

After the capsule is discharged with the feces, use MagKey to attract thrust magnets in capsules, then find and recycle capsules.

Lastly, take the capsule to hospital for further analysis.

Fluorescence Reader

Inspired by our Synthetic Biology Club, we decided to build a fluorescent reader that is cheap enough for high school lab to buy, as well as having an acceptable accuracy of measurement.

Figure 2 design of Fluorescent Reader
There are 2 optical paths in our fluorescent reader
Path1: Red light to Detector (right to left on Figure 2)
Path2: Blue light exposures sample → sample GFP fluorescence excited and travel at all directions → [part of green fluorescent travel through Filter that is only permeable to 500-540nm wavelength] →Lux-meter detects fluorescent intensity.

When using light path 1, the reader is in Light-absorption mode:
1. Use filter①, 600-650nm narrow band (pass red light).
2. Insert blank solution, red light penentrate blank solution and measures 100% intensity Ib.
3. Insert control or sample solution, red light gets through the control or sample, and light intensities Ic and Is are measured.
4. Sample OD, S600=-lg(Is/Ib), control group C600=-lg(Ic/Ib)

While using light path 2, the reader is in Fluorescent intensity mode:
1. Blu-ray excites GFP, filter②, 500-540nm narrow band (pass green light from GFP).
2. Testing the sample fluorescence intensity Fs and control group fluorescence intensity Fc by Lux-meter.
3. The relative fluorescence value of the sample fs=Fs/S600, the relative fluorescence value of the control group fc=Fc/C600
4. Calculating the fluorescence ratio R=fs/fc to judge the extent of inflammation in the intestines.
. We tested the device on our Synthetic Biology Club activity, and it seems the significant digit provided by the Lux-meter is rather low. We considered to change the Lux-meter to more sensitive photodiode and calculate the result by microcontroller such as Arduino.
. If the fluorescent reader’s accuracy could be increased evenmore while keeping the price low, we believe it is possible to sell fluorescent reader with the capsule and let the patient analyse the test result in home.