The fastest way to test for the presence of a substance in any media is via a visual reaction. Prominent examples being pregnancy tests or COVID-19 tests. We opted for a whole-cell biosensor approach. Naturally occurring proteins can be used to detect certain substances with the cellular response being modified to be a visible reaction, like fluorescence or the creation of a colored substance. Whole-cell biosensors are advantageous because of their independence of sample processing, simple operation, and cheap production.[1]
The approach we chose is based on proteins found in naturally occurring defense mechanisms against ß-lactams: BlaR1 from Staphylococcus aureus and VbrR/VbrK from Vibrio parahaemolyticus. These proteins were integrated in E. coli and either applied onto a paper strip or an alginate capsule with different corresponding response mechanisms. On the paper strips the detection of β-lactams leads to the expression of a β-galactosidase leading to a reaction analogous to the process of the commonly used blue-white screening. Inside the alginate capsules the response to detection of antibiotics is the expression of GFP, which is easily detectable via fluorescence measurements. Both systems simply require to be in contact with a water source without any further processing.
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BLISS only requires commercially available materials, such as E. coli, Whatman filter paper or CaCl2 and alginate, making the production of these systems extremely cost-effective. It is also environmentally friendly, as the alginate capsules are entirely bio-degradable and the paper strips can be recycled, contributing to a more sustainable, circular economy.
The production of our systems can easily be upscaled since there is no need for protein purification or similarly complex procedures. The plasmid containing the entire detection construct can be stably integrated into the genome of E. coli, at which point they only need to be cultivated and applied to either the paper strip or the alginate capsule. These application procedures can also be easily upscaled, making the entire production affordable and efficient.
The most important demographic we want to reach with BLISS are laboratories, wastewater facilities and hospitals, because they are sources and even victims of antibiotic contamination. Our products were specifically designed to allow fast and easy examination, with the alginate capsules even being able to constantly scan flowing water sources, which is especially useful for wastewater facilities. Other possible end users include authorities responsible for nature conservation, agriculture and food. Offering these authorities efficient systems for testing water sources will lead to faster responses and minimize potential damage.
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Safety of the production line:
E. coli poses close to no harm and the chemicals used are also not dangerous, so there was no
need for major safety precautions during our work. However, since we genetically modified our cells,
we were required to comply with directives concerning GMO work given by the EU. Our project was
classified under S1 because we are genetically modifying our organism in a way that is not dangerous
for humans.
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Safety of the end user:
Even though BLISS contains GMOs, our systems can be used anywhere, since the cells aren't released
into the environment. They are also very simple to use and pose no threat to the user in any way.
The paper strip requires a few microliters that can be added dropwise to the strip. The genetically
modified bacteria never escape into the environment. The paper strips can be stored for up to three
months [2]. In this time the cells lie dormant, without multiplying or any other notable activity,
allowing them to be stored without any safety concerns. Alginate capsules entrap bacteria and are
permeable for water and water-based solution. They should be used right away, as they can be only
stored for up to 10 days [3].
Diversity of detectable antibiotics and even other
pharmaceuticals:
This is the biggest improvement of the system that we have nearly accomplished. The molecular
dynamics between the binding pocket of a receptor and a ligand can be modelled. Solely detecting
antibiotics does not fit our vision of versatility. While we benefit from pharmaceuticals like
diclophenac and others, they have shown to be harmful to the environment. Adapting our system to a
variety of compound that are currently overlooked when assessing water quality is the future goal.
Making results quantifiable:
Our whole-cell biosensor is sensitive, but not as sensitive as we wished it to be. It is qualitative
but quantification of antibiotics concentration needs to be improved for it to be a commonly used
testing system for our end users.