Difference between revisions of "Team:Technion Israel/Design"

Design

FlashLab parts

The device is composed of a commercial fluidic chip:

The chip is open on the button part and closed with a standard microscope cover glass (0.3 [mm] thick).

FlashLab setup

The setup of the device is composed of two parts, as shown below (Figure 2): a. The channel is filled with colored E. coli bacteria suspended in motility buffer. b. The sample is loaded into one of the entry slots.

FlashLab test

Once the sample is loaded, it diffuses into the channel. If the sample contains a repellent, the bacteria will react and move away from it as shown below:

The chemotactic response will result in visible changes in the bacterial concentration throughout the chip: Very low concentration in the immediate area of the slot in which the sample was loaded, adjacent to a higher concentration of bacteria created due to the fleeing bacterial population. (right picture, figure 1:4). These changes will be visible to the naked eye, as the higher concentration of colored bacteria results in darker color (blue gradient, figures 1:3 and 1:4). If the sample does not contain the target material, the bacteria will not react and no gradient will be formed.
For more information see mathematical model.

Results

FlashLab parts

The setup for the device is as shown in "Design and Implementation". The bacteria, UU E.coli strain with a cloned Tar-PctA receptor , was taken from a petri dish and diluted in of motility buffer. The Chemo-repellent used was of TCE in concentration of 0.02[M] while the control was motility buffer. The pictures were taken in differential of 5[min] apart.

After 20[min] , a noticeable color gradient is formed in the channel. on the far left, a relatively light shade. adjacent to it, an area with a darker tone and from there up to the right end of the channel, the color did not change at all. This fits the theory perfectly, as the lighter shade is caused by colored bacteria moving away from the repellent. The darker shade is the clustering of bacteria in the chemo-repellent diffusion limit. All other bacteria in the channel, were not exposed to the repellent and did not react accordingly.

For more information see chip experiment protocol

Outlook

We developed FlashLab, the hardware of the S. Tar platform. S. Tar is based on the Chemotaxis phenomenon and offers a wide library of “expert” strains for the detection of materials that do not naturally induce chemotactic movement in the native E. coli. This was obtained using synthetic biology tools, including computational design which allowed us to create new mutations in the Tar chemoreceptor. These mutations resulted in novel interactions between proteins and ligands.

FlashLab is a tool which combines both biological and mechanical aspects. As we mentioned before, computational tools were required as well in order to develop the S. Tar platform. This multidisciplinary innovation was achieved thanks to the different backgrounds of our team members. Our team is comprised of students from the faculty of Biotechnology who were in charge of the Tar chemoreceptor modification in the wet lab, students from the faculties of Mechanical engineering and Chemical engineering who developed the mathematical model for the flow and chemotaxis profiles inside the microchannel and students the faculties of Electrical engineering and Computer Science who were in charge of the computational design aspects of the project. The unique composition of our team was crucial to the construction of a complex but elegant system.

There are several methods for detection of small molecules. The next table summarizes the most used methods in this field:

FlashLab advantages as a detection tool:
- Cost effective The only major cost is the fluidic chip which costs about 15$ and can be reused multiple times.
- Fast as shown in the experiments, the detection takes about 30 minutes. This is faster than most other bacterial detection (based on transcription and translation) and most laboratory tests (HPLC).
- Versatile The S.Tar system enables this device to detect a variety of materials: hormones, amino acids, organic compounds etc.
- Sensitive Bacteria can sense extremely low concentrations of target material.
- User friendly The setup of the system is an easy two part process. To reuse the chip it is only required to flush the channel with water and to dry it up. In comparison, Flashlab, although not the most accurate, offers a fast, cheap, easy to use and versatile detection.
(For further improvement see "Design and Development").