Amplification trick increases sensitivity of water toxin detection by 10 times

Electric instruments can function unplugged, but they sound better when connected to an amplifier. Similarly, low concentrations of toxins and other small molecules in the environment or in the human body can emit quiet signals that are undetectable without specialized laboratory techniques.

Now, thanks to a “cool trick” in biochemistry used to adapt a sensing platform already deployed by Northwestern scientists to measure toxins in drinking water, researchers can It is now possible to detect and even measure chemicals at low enough concentrations to be used outdoors. By installing a circuit similar to a volume knob to “amplify” weak signals, the researchers open the door for the system to be applied to the detection and monitoring of human diseases, including nucleic acids such as DNA and RNA, and bacteria. Opened. As E. coli.

The findings, which describe a system that is 10 times more sensitive than previous cell-free sensors built by the team, were published in the journal Nature Chemical Biology.

“While biosensors recycled from nature could in principle detect a full range of pollutants and human health markers, they are often not sensitive enough as is,” said corresponding author and Northwestern synthetic biologist. said Julius Lacks. “The addition of a genetic circuit that acts like an amplifier allows this biosensing platform to meet the level of sensitivity required for environmental and human health monitoring applications.”

Lux is a professor of chemical and biological engineering and co-director of the Center for Synthetic Biology at Northwestern University’s McCormick School of Engineering.

Developed “water pregnancy test”

ROSALIND’s original model was able to detect 17 different pollutants in a drop of water and glowed green when pollutants exceeded U.S. Environmental Protection Agency standards. The second model allowed the platform to calculate different concentrations of contaminants, creating something more advanced than a “water pregnancy test.”

Lux and his team used an approach called cell-free synthetic biology to create ROSALIND, which takes molecular machinery such as DNA, RNA, and proteins from cells and reprograms them to perform new tasks. .

Useful bugs in the system

Synthetic biologists working with DNA and RNA often encounter a useless nemesis called the T7 RNA polymerase enzyme. Lux likens the role of sending out the output signal to a battery in a radio. In most cases, this enzyme acts like a bug in the system, munching away on pieces of RNA it wasn’t meant for and can wreak havoc on nucleic acid circuits. But Lux wondered if they could use that to their advantage.

Lux uses the history of transistor radios to develop a sensing technology his team built called ROSALIND (named after chemist Rosalind Franklin and short for “Ligand-induced activated RNA output sensor”). Describe the advancement of the platform.

“When you build your first transistor radio in an Electronics 101 class, you get a radio signal, but there are a lot of problems,” Lux says. “If you walk behind a tree you lose the signal, and as you get closer to the source it gets louder. In future generations of that radio, additional electronic circuitry was added to control and correct them.” Repetition is basically just adding a volume knob to your radio.”

Researchers have discovered a way to boost the signals of input molecules using DNA nanotechnology’s signal amplification trick, which allows circuits to recycle and regenerate inputs. Once a signal is generated, a “bug” eats it, recycles it, and generates another signal. As a result, the team was able to detect molecules such as antibiotics and heavy metals at a fraction of the concentration of previous iterations.

“With ROSALIND, we created a new system to amplify signals,” said lead author Dr. Jenni Li. candidate in the Lux lab. “A great trick in biochemistry allows us to sensitize a system to detect compounds at lower levels without changing the actual biosensor protein. This is all done in a nucleic acid ‘circuit’. Masu. ROSALIND 3.0 has improved sensitivity and can now detect nucleic acids, whereas previously only small molecule compounds could be detected. ”

Rosalind at work

Previous iterations of ROSALIND have already been deployed in real-world settings. For example, ongoing field studies in the Chicago area have detected lead in drinking water. Lux said the new elements of the team’s “3.0” model can be easily applied to this and other projects.

“We are also developing ROSALIND for the detection of human health markers, food quality markers, and agricultural compounds, opening up applications for this platform technology,” Lux said. “This new sensitization approach is common and means that in the future we will be able to develop sensors more quickly that can detect compounds at practical levels.”