Feasibility Analysis

We verified that our initial idea works and that we can actually get a moving GFP band in the channel responding to different input acetaldehyde concentrations!

In order our smoColi bacteria to start reporting acetaldehyde in the air (when GFP band appears at the begining of the channel), system should be supplied with around 44.05 mg/L acetaldehyde. In order for the band to be able to form at the very end of the channel, the input acetaldehyde concentration should be 2420 mg/L.

Figure 1: GFP vs. increasing acetaldehyde input (both in μM). The band appears when the acetaldehyde concentration is in the range of 500-1500 μM

Video 1: Steady state simulation sweep from 1 to 2500 mg/l acetaldehyde concentration in reservoir: 3D GFP concentration in mol/m3, 5 slices through the channel. Channel width: 2 mm, Channel length: 5 cm. Press play to start video!

This acetaldehyde concentration is toxic for the cells. However, with single cell model parameters tuning, we got the band at lower acetaldehyde concentration (we haven't done the COMSOL simulation with those values yet). The tuning of the parameters doesn't affect the feasibility of our design at any way, since it just affects the input acetaldehyde concentration needed.

Process Design

After simulating our system in COMSOL, we came to the following conclusions that helped us designing the channel experimentally:

• E. coli can generate a gradient by degrading a substance replenished by diffusion in an agarose-filled channel.
• It can do so within a reasonable experimental timeframe (within several hours).
• It can do so within reasonable channel lengths (several centimeters.
• Channel diameter is irrelevant for our system.
• As mentioned, we need 44.05 mg/L of input acetaldehyde concentration for the band to appear, 2420 mg/L for it to come to the end of the channel.