Difference between revisions of "Team:XMU-China/Description"

Heavy pollution has long plagued the people. How to detect the concentration of heavy metal ions and how to decrease the detection limit as much as possible have become a challenging task.

Now the most common and sensitive method of detecting trace heavy metals is atomic absorption spectrometry(AAS). But this method requires expensive instruments, and the operation is also cumbersome. So the AAS is limited to professional testing organizations and scientific research institutions to use. In addition, although there have been test paper, detection kits and other low-cost products which can be used to detect heavy metals, they also face the problem of low efficiency, poor sensitivity, tedious work and so on. So the existing detection technology is not suitable for the general population to use.

Although there were many iGEM teams also trying to design a variety of detecting systems to detect pollutants, they have many defections that the detection limit is high and that the detection time is long. So to find a better way of detecting very small quantities of heavy metals, something like the biological signal-amplifiers, the microfluidic chips and the portable hardwares is are necessary.

An interesting method to detect the concentration of ions using Escherichia coli is to select the corresponding metal-sensitive promoters binding with the reporter genes like the fluorescent protein genes. By constructing this kind of recombinant plasmids, the concentration signal can be transferred into the semi-quantitatively detectable signal like electric current and so on. But the detection limit is so low that only high level accumulation of heavy metals in the environment can be detected. To solve this problem, we aim to develop an amplifier to detect semi-quantitativly the concentration of the heavy metal ions including the metals with small volume.

A sensitive detector for harmful ions in water based on a chip


Arsenic contamination in drinking water has long been a serious problem in many countries throughout the world, including China and the US. So XMU_China hopes to provide a sensitive and user-friendly device to detect arsenic in water. A microfluid chip is designed and produced to achieve our goal. The chip is a arsenic detector containing genetically modified E.coli that is able to express green fluorescent protein or lacZ in response to the concentration of arsenic. By calibrating the fluorescence intensity or current strength caused by luciferase or lacZ respectively, a whole range of arsenic levels in water can be detected.
We also plan to use this chip model to detect other metal ions such as iron and mercury . To simplify the process, we will adopt a certain universal approach by constructing a common intermediate which can eliminate the differences among detection of different metal ions. And T7 induced expression system is used to realize the effect of amplifying the signal in response to these ions. What’s more , we try to explore potential application of iLOV, a kind of small FMN-based fluorescent protein, to detect and recycle these harmful ions because of its inherent, binding properties towards them with high affinity.