The first step was to set the protocols of production for each device (for the PCR we followed our PCR protocol available on<a href="https://2012.igem.org/Team:Grenoble/Biology/Protocols/PCR_1">biological section</a>.)
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The first step was to set the protocols of production for each device (for the PCR we followed our PCR protocol available on <a href="https://2012.igem.org/Team:Grenoble/Biology/Protocols/PCR_1">biological section</a>.)
Design of the device and comparative study of cost assessment
Specifications
Based on the requirements of the medical field (see the section meeting for further details), we set our pathogen detection specifications. So, sEnsiColi should be:
Sensitive
Reliable (little false positives)
Fast
Easy to use
Lower in price than the current methods.
The modeling part deals with the first three specifications: the deterministic model gives an answer for the sensitivity and the rapidity while the stochastic model gives an answer for reliability.
In this section we will especially deal with the easiness of use and the cost assessment of the device.
Design of sEnsiColi
Regarding the specifications above, we set two possible designs for sEnsiColi.
The first one is intended for prevention purposes such as assessing the contamination level of hospital’s rooms. The design of this detection-kit is given by the picture below:
This first prototype is easy to use: A sample of the surface to test can be taken by a swab and then put in the test tube containing the bacterial solution. After about 5 hours we can check the tube. If we have a fluorescent response then the tested surface is contaminated by Staphylococcus Aureus. (see modeling section entire system for an assessment of time response)
Then, sEnsiColi average response time is at about 5 hours which is twice the response time of a PCR (PCR needs between 2 and 3 hours to deliver the result). Then in term of rapidity sEnsiColi isn’t really competitive compared to a PCR method.
However, if we examine the reliability of the kit (see modeling stochastic section) it appears that thanks to the designed And Gate in the amplification module, the probability of having a false positive response doesn’t exceed 0.43%. Compared to the reliability of a PCR (93% [1]) this value is highly satisfying.
In order to enhance even more the reliability of our system, we decided to set a second design based on a 96-well plate. Thus, the probability that a false occurs diminishes significantly: If no Golden staph has to be detected, no more than one sample out of 96 gets a visible output signal.
To sum up, we designed two different detector prototypes:
A detection-kit that is absolutely easy to use and needs no qualified staff to use it. This test is approximately ten times faster than a traditional plate test (48h) and twice slower than a PCR (from 2 to 3 hours) as it needs 5 hours to give a visible output signal. Besides, thanks to this system, the probability of having a false positive response is 0.43%. Its design makes it a competitive candidate for assessing contamination level in medical environment
A 96-well plate kit for diagnosis, easy to use, fast enough (5 hours) and above all reliable to 99.99%.
Now that we validated the design of our kit and most of its specifications, you are probably eager to find out if our test is lower in price than the current detection methods. You can have a look at the next section to get the answer.
Comparative study of cost assessment
We wanted to make sure that sEnsiColi would be competitive in term of price. So we conducted a comparative cost analysis between the mostly used detection methods in the CHU and our two possible designs of sEnsiColi.
For the cost assessment, we followed a very specific process in order to have a precise and reliable result.
The first step was to set the protocols of production for each device (for the PCR we followed our PCR protocol available on biological section.)
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