A team of researchers at Northwestern University has repurposed a nearly 20-year-old platform, initially used for detecting protein interactions with DNA and COVID-19 testing, to develop a highly sensitive tool for water contamination detection. This technology combines synthetic biology and nanotechnology to create a platform capable of chemical monitoring.
The new system can detect metals such as lead and cadmium in water at concentrations as low as two and one parts per billion, respectively, within minutes. The research findings were published in the journal American Chemical Society Nano by a cross-disciplinary team from Northwestern’s McCormick School of Engineering.
The test utilizes nanomechanical microcantilevers coated with specially designed DNA molecules. These cantilevers are made of silicon and are easily reproducible. When exposed to target chemicals, transcription factor biosensors unbind from the DNA, causing the cantilever to "debend," which can be precisely measured to detect contaminants.
Northwestern synthetic biologist Julius Lucks contributed his ROSALIND technology to the project. This cell-free biosensor uses transcription factor biosensors configured to control gene expression by binding and unbinding DNA. During the COVID-19 pandemic, Lucks observed the microcantilever technology being adapted by professors Vinayak P. Dravid and Gajendra Shekhawat for SARS-CoV-2 detection. Inspired by this application, Lucks proposed using his lab-engineered DNA on cantilevers to detect chemical toxins.
Dravid highlighted the advantages of this approach: “These are micro- and nanosystems that don’t need a lot of viral material to make a difference,” he said. “Microcantilevers can give you a faster turnaround, within two or three minutes.” He also noted that unlike most sensors relying on one protein, this system can target multiple substances simultaneously.
Dravid holds positions as Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering and is affiliated with several institutes at Northwestern University. Lucks is a professor of chemical and biological engineering at the same institution.
The research team began testing with tetracycline due to its extensive use in synthetic biology before moving on to lead and cadmium detection down to parts per billion levels—a record for biosensor detection methods.
Future plans involve simplifying the technology further since it currently requires specialized equipment for visualizing microscopic movements. The researchers aim for broader applications in human health monitoring for bodily toxins and environmental safety standards enhancement.
This work was supported by grants from the Northwestern McCormick Catalyst Award, National Science Foundation (grant no. 2319427), and Northwestern University Synthesizing Biology Across Scales National Research Training Program (grant no. 2021900).