By Fern Alling
Medill Reports

Nearly three-quarters of all service lines in Chicago’s public water system are made of lead.

A 2024 analysis by the Natural Resources Defense Council on Environmental Protection Agency data found more than 387,000 lead service lines in the city. The federal government banned the installation of new lead pipes in 1986, but thousands still remain.

“Chicago has a unique infrastructure issue with lead,” said Julius Lucks, co-director of Northwestern University’s Center for Synthetic Biology. “It’s got the most lead pipes (of any city) in the country because of this ordinance requiring lead pipes to be used in single-family homes.”

At-home testing kits are available at some home improvement stores, but it’s hard to know how accurate they are. According to a 2021 study published in the journal Environmental Science and Technology, 12 of the 16 at-home tests the researchers evaluated were “not suitable for drinking water analysis.”

Government testing is far more reliable but comes with its own drawbacks. Chicago residents can test their water for lead through a free city program, but results can take weeks to get back to the homeowner. And the gold-standard testing techniques the EPA uses require bulky equipment that can’t be taken into homes.

That’s why Lucks and his team are using biosensors to develop at-home test kits for lead in drinking water that provide gold-standard results in minutes, not weeks. The lab’s work could make on-demand, at-home lead testing more accessible for Chicagoans.

Lucks and his team aren’t the only ones using synthetic biology to develop water quality tests. What makes their work unique, Georgia Tech synthetic biologist Mark Styczynski said, is the focus on putting the power in users’ hands.

“You can make sensors that get put into a clinical lab, or get put into an analytical lab, and yeah, that’s great, but is it really making that much of a difference?” Styczynski said. “Making it such that it can really be in the hands of anybody, that has the potential for much broader impact.”

Building a biosensor starts with bacteria. Even though they don’t have brains, bacteria cells are able to detect and respond to threats in their environments.

Biosensors exploit these natural mechanisms to genetically mimic a system that detects substances harmful to humans and reacts by creating a measurable byproduct.

Some biosensors are made with genetically modified cells. But the Lucks lab lead tests are cell-free.

“We don’t use cells because keeping them alive is tricky,” said Tyler Lucci, a chemical and biological engineering Ph.D. candidate with the Lucks lab. “It’s a lot easier for us to just take what we need out of them and go about our way.”

The current iteration of the Lucks lab lead test relies on a mechanism called a DNAzyme. Dozens of labs use DNAzymes to detect lead in water samples, but those tests require specialized lab equipment. The Lucks tests, on the other hand, are designed for the average user who doesn’t have a micrometer measure on hand.

DNAzymes are a portmanteau of “DNA” and “enzyme.” Enzymes are biological catalysts. They create environments that make a chemical reaction far more likely to happen.

Think of an aspiring Olympic gymnast. Children don’t just grow up and become world-renowned athletes by themselves. A lot of things need to go right for them to succeed. They need consistent training, healthy food and an innate talent. Like the parents of a gymnast who hired the best coaches and nurtured their child’s dream so they could make it to the world stage, enzymes bring the right ingredients together in just the right way for a chemical reaction to occur.

DNAzymes function in the same way other enzymes do, bringing those chemicals together in the right way so a reaction can occur. But while most enzymes are made of proteins, DNAzymes consist of two linked DNA strands.

Each strand has a job. The enzymatic strand’s job is to react – when it touches lead, it breaks away from the substrate strand. More lead in the sample means more chopped-up substrate strands, a veritable strand soup.  The substrate strand’s job is simply to be noticed. The test kit’s test strip turns pink when substrate chunks accumulate. And, just like a COVID-19 test, you’re in trouble if you end up with two pink lines.

Juliana Feng, a medical Ph.D. student, is part of the team bringing the second round of tests to study participants this month. She said they plan to complete 25 tests in Evanston and 25 in the southeast side of Chicago.

Feng said the first round of testing was really educational.

“I, like many engineers, don’t have the experience to actually go out in the field and talk to people that are actually using their products,” she said.

Insight into user preferences is one of the benefits of field testing. Some study participants struggled to use the small test tubes, and those with limited mobility found it challenging to open screw caps on the tubes. Feng said she would’ve missed those challenges for users since she’s used to working with lab equipment.

To ensure the results are accurate, additional samples from each study participant are analyzed using EPA standard techniques. No test is perfect, so scientists sometimes adjust their tests to lean more toward false positives or false negatives.

False positives are preferable in theory. Better for someone with safe water to think it’s contaminated than for someone with contaminated water not to know they have a problem. But Feng said it was hard to see the consequences of a false positive play out in real time.

“If you’re not doing the work, you don’t realize,” she said. ”You know that it’s bad to keep people hanging, but you aren’t the person saying, ‘Actually, I can’t tell you when your results (will be in).’”

The lab’s work is funded by multiple grants, including one from the Department of Defense and another from the National Science Foundation. The Department of Defense issued a stop-work order for its grant to the Lucks lab, effectively cutting off the funding it provides. However, the lab is still moving ahead with the biosensor project with money from other sources. Lucks said he hasn’t heard anything about their NSF grant but acknowledged many researchers are worried about the future of their funding.

The Lucks lab is adapting quickly in response to the shifting funding landscape to keep the lead project moving forward. The second round of field testing began this month, and the first field test of the updated biosensor was completed April 21. Even with funding uncertainties hanging over their heads, the lab is eager for the latest results.

“It’s super exciting,” Feng said. “A lot of us are super excited to see what the data shows.”

Fern Alling is a graduate student at Medill specializing in health, environment and science reporting. You can connect with them on LinkedIn.