About This Project

Drinking water contaminated by metals, most notably lead, poses health risks to children and adults alike. However, commercially available at-home detection systems cost about $30 per test. Given the recent lead scare in Flint, Michigan and high levels of lead in many cities across the world, we plan to create a inexpensive biosensor suitable for use at home.

Ask the Scientists

What is the context of this research?

In 2014, the Collins group at MIT published a paper detailing a paper-based sensor made by freeze-drying cell-free extract and the biosensor onto paper. The cell-free extract contains the transcriptional and translational enzymes necessary to produce proteins and it is activated by rehydrating the paper with water. The paper sensor can be stored in a refrigerator and costs less than a dollar to produce. The Collins group added RNA-based biosensors to detect small molecules, and in the presence of the molecules the sensor produced a colorimetric response in less than an hour. We are expanding this fast, easy-to-use system to detect metals.

What is the significance of this project?

Our sensor will benefit society by enabling citizens to test their drinking water for less than a dollar. The current DNAzyme sensor that we are developing detects thallium and lead. The circuit can also be adapted to any other toxic metal contaminants including copper, arsenic, and antimony.

Technologically, our system incorporates novel functions for DNA. Our sensor utilizes DNAzymes that cleave in the presence of thallium or lead, and can be modified to work with any DNAzyme. The cleavage produces a DNA strand that triggers a toehold switch, resulting in protein expression and a change in color of the sensor. As far as we know, we are the first to pair DNAzymes with toehold switches such that a DNA molecule acts as a trigger.

What are the goals of the project?

The funds collected will allow us to complete the proof-of-principle research that we have already started and expand to more metals. This requires custom made DNA and cloning. To determine the effectiveness of the DNAzymes, we use electrophoresis techniques to see whether our DNAzyme cleaves in the presence of our metal samples. If the previous step is successful, we test our sensor in cell-free extract to see if there is a color change.

Along with testing our DNAzyme, we experiment with our toehold switch to determine its reactivity. This has become an optimization process as we change the amount of cell-free extract and concentration of DNA needed.

After we are successful on both fronts, we will begin experimenting with the freeze-drying process.