Team:Technion Israel/Design
Introduction
FlashLab, a novel detection tool based on the chemotaxis system of E. coli
bacteria
. It utilizes chemotaxis to concentrate bacteria expressing a chromo-protein, this in turn, creates a visible gradient in color – detection of a target material.
FlashLab is an application of the S.Tar project. S.Tar is a platform for programmable chemotaxis which allows the user to select the material that will induce a bacterial chemotactic response. For more information please visit S.Tar page
Using S.Tar technology, FlashLab can detect a variety of materials: hormones, amino acids, organic compounds etc.
Fig. 1: Detection tool explanation
Fig. 2:The geometry 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 3):
Fig. 3: The chip setup.
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:
Fig. 4: Chemotaxis reaction in the chip.
This will cause changes in the bacteria concentration: very low concentration, where the repellent diffused
to, next to a very high concentration, where the bacteria moved to (right picture, figure 1:4). Those changes
will also be visible, as the higher concentration of colored bacteria manifests itself in a stronger color
(blue gradient, figures 1:3 and 1:4).
If the sample does not contain target material, the bacteria will not react and no gradient will form.
For more information see mathematical model.
Results
FlashLab parts
The set up for the device is as shown in "Design and Implementation". The bacteria, E.coli strain #$%^&@#$%^, was taken from a petri dish and diluted in 180[µL] of motility buffer. The Chemo-repellent used was 30 [µL] of #$%^&@#$%^ in concentration of α[M] while the control was motility buffer. The pictures were taken in differential of apart.
Fig. XYZ:ABC.
Following γ[min], a noticeable gradient of blue color formed in the chip's channel. on the far left, a relatively
light shade. Next to it, an area with a darker tone and from there up to the right end of the channel, the tone
didn’t change at all. This lines up with 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 so didn’t react.
==========For more information see chip experiment protocol==========
Outlook
FlashLab has advatages as a detection tool:
- Cheap The only major cost is the fluidic chip and one costs about 15$ and can be reuse multible times.
- Fast as shown in the expermints, it takes about 30 minutes for detection. This is faster then most other bacterial detection (based on transecription and translation) and most laboratory tests (HPLC).
- Verstile The S.tar system enable this device to detect verity of materials: hormones, amino acids, PCE etc.
- Senstive: Bacteria can sense extrimly small traces of target material.
- Easy to use: The set up of the system is an easy, two parts process. To reuse the chip you only need to flush the channel with water and dry.
References:
1. KELLER, Evelyn F.; SEGEL, Lee A. Model for chemotaxis. Journal of theoretical biology, 1971, 30.2: 225-234.
