iGEM Bielefeld 2015

Heavy Metals

We detect several heavy metals with a single test strip.

Heavy metals have been part in a lot of iGEM projects over the last years, so why work with them again?

Heavy metals are still a major problem. Therefore, they have been part in a lot of iGEM projects. There are many concepts to create heavy metal sensors. Some of them work extraordinary well. But most of these sensors never made it to real world applications. We aim to make a use of well characterized sensors as well as concepts and new ideas. All this sensor systems shell work on the same principle, so that we can use them to create a modular easy to handle paper based cell free test strip for detection of more substances, heavy metals in this case, in parallel.

"In my opinion the test stripe system has great potential in the field of monitoring contamination in industrial wastewater. It`s a fast and easy available system for qualitative control of several heavy metals.” (Dr.rer.nat. Andreas Bermpohl, manager of Biotec GmbH)

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Why heavy metals?
Heavy metals are part of Earth’s crust. Therefore, they do occur naturally in our environment. (Heavy Metals - Lenntech) In low doses some of them as copper or nickel are even essential trace elements for animals and humans (Rashmi Verma and Pratima Dwivedi 2013). A major problem is their bioaccumulation, which leads to toxicity and long term effects which include fatal diseases like cancer (Martin et al. 2009), Parkinson`s or Alzheimer’s disease (Gaggelli et al. 2006) (figure 1).

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Which heavy metals?
The heavy metal sensors we chose for detection are specific to arsenic, copper, chromium, lead, mercury and nickel. Their concentrations in drinking water are regulated by the WHO, because of their immediate and long term health effects (figure 2).

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Our biosensors
We decided to work with already existing, well-characterized sensors as well as with established but not well-characterized concepts of other teams and moreover create new sensor systems. Therefore, we established a basic construction plan for our sensor systems, which is based on a promoter with a specific operator region in front of a super folder GFP (sfGFP), which was used for detection trough fluorescence analysis. In addition we used fitting activators or repressors for our inducible promoters under the control of BBa_K608002, which consists of a constitutive promoter with a strong ribosomal binding site (RBS) (figure 3). We combined these into a device consisting of constitutive promoter and RBS reverse and the promoter and operator region in upstream of the sfGFP. So we have repressor or activator constitutively expressed in reverse orientation. This was done to minimize the background transcription of the inducible system in upstream of our heavy metal promoter operator system. In addition, these devices are optimized for the usage in a cell free protein synthesis(CFPS). This is the basis for the development of cell free biosensors on a test strip, which can be used to detect several heavy metals at once in the open field.

Click on the test strip for more information about the heavy metals and how they can be detected: