We'll know it when we sense it
Ariel Furst, assistant professor of chemical engineering, harnesses the potential of electrochemistry to develop faster, more sensitive, even self-powered diagnostic tools.
Thanks to COVID-19, Americans have become more familiar than ever with some of the major challenges of lab testing and diagnostics. From healthcare to environmental remediation to clean energy, researchers are working to develop diagnostic methods and devices that are affordable, accessible, and deliver accurate results quickly, even when testing for unknown compounds in complex solutions.
For Ariel Furst, a new faculty member in the MIT Department of Chemical Engineering, electrochemistry is a key to solving these problems. “Electrochemistry is an exceptionally powerful tool that allows you to simultaneously complete chemical conversions while also sensitively and specifically monitoring interactions at the same surface,” she says. Equally important, the instrumentation is inexpensive and easy to use.
A unique aspect of Furst’s research is the use of chemical insights and new chemistries to improve how biomolecules interact with electrodes. These biomolecules—DNA, proteins, antibodies—usually are not specifically attached to surfaces. This decreases sensitivity and increases the amount of noise in assay readings. “By developing sensors that use specific biochemical interactions, we can get significantly increased sensitivity and specificity,” she explains.
In the area of human health, the Furst Lab is focused on some of the most common microbial infections: urinary tract infections and sexually transmitted infections. Typically, a doctor takes a tissue or fluid sample, sends it to a lab to culture, and gets results in a few days. “At that point, you’ve already been prescribed the antibiotics, and that can be problematic if they’re the wrong ones.” Not only is the patient’s recovery delayed, but if the infection is an antibiotic-resistant strain, it may have had time to become even more resistant, exacerbating a global threat to human health.
In fact, secondary microbial infections have emerged as a major concern in the treatment of patients with COVID-19. Furst points to a March 2020 study published in The Lancet showing that 15 percent of patients with COVID later acquired bacterial infections, which resulted in a 50 percent mortality rate.
This kind of simple, rapid testing would revolutionize how we think about diagnosing and treating infectious disease.
Furst and her colleagues are developing platforms that would enable bedside testing of antibiotic resistance with results in half an hour, not half a week. This kind of simple, rapid testing would “revolutionize how we think about diagnosing and treating infectious disease.”
“I’ve always been motivated by the phrase ‘benchtop to bedside,’” Furst says. In the case of infectious disease testing, it’s a literal goal as well as a valuable reminder that moving from lab research to real-world impact is a multistep, multi-stakeholder process. “A lot of academic research gets stuck in between those two, even at MIT with all of its internal resources.” Industry partners, with their access to manufacturing pipelines and knowledge about scalability, can help bring breakthrough science to real-world impact.
Instead of looking for specific compounds, which aren’t always known, some of the chemistry Furst is developing looks at how the compounds behave in the human body.
Take endocrine disruptors, a family of pollutants that are chemically dissimilar, but that all bind to the same estrogen receptors. One of the most well-known endocrine disruptors is bisphenol A (BPA), a compound that’s widely used in household plastics, food packaging, and grocery store receipts and has been linked to decreased fertility, certain cancers, diabetes, and obesity. BPA becomes problematic when enough of it leeches into food or water, which makes testing both necessary and complicated.
Existing testing methods include cell-based assays. Like Furst’s sensors, they use the hormone receptor, but cell-based assays take time, training, and a lab environment to execute. Fluorescence-based biosensors are another testing method. These are difficult to read in the field and don’t work well in complex chemical compounds, whether that’s a wastewater stream or a bottle of infant formula.
The Furst Lab’s biosensor for detecting endocrine disruptors uses cheap electrochemical instrumentation, takes half an hour to run, and costs under $2 per assay.
“Our biosensor is the best of both worlds,” Furst says. “It’s rapid electrochemical detection, so it’s cheap instrumentation, and we use disposable electrodes. It takes only about half an hour to run and costs under $2 per assay on a non-industrial scale.” For a family concerned about BPA in household plastics and food packaging, a consumer-grade test like this could provide invaluable reassurance.
Many companies have eliminated BPA in their manufacturing, but as Furst points out, it’s not a given that what they’ve replaced it with is safe. This is another reason why sensors that detect behaviors rather than chemical structures are so important: There aren’t enough accessible sensors and assays to keep up with the pace that new chemical formulas are brought to market.
“People are detecting new problematic compounds every day,” she says. In the Boston area, for example, a pesticide sometimes used for mosquito remediation affects neurotransmitters in a way that’s similar to sarin gas, a toxic nerve agent. Developing sensors that look at those neurotransmitters eliminates the need to know what specific chemical you’re testing for.
Environmental remediation, like human health care, also requires reliable and easily deployed methods for detection and treatment in complex solutions. Furst is working with microbes that can metabolize carbon sources, including pollutants and wastewater components, and secrete electrons, essentially generating their own power.
“We’re interested in understanding the micro-scale interactions between these microbes that can be deployed in microbial fuel cells and an electrode surface,” she says, and then harnessing that interaction to produce devices that can sense pesticides in agricultural settings or be deployed as a self-regulating wastewater treatment system. Think of it as an algae-eating fish in a home aquarium—one that can be engineered to detect and destroy specific pollutants and produce energy while it does so.
Companies are already beginning to use microbial fuel cells in wastewater treatment, but when it comes to harnessing the energy they produce, there are two primary challenges, as Furst describes: First is that microbes that can do this extracellular electron transfer are very slow growing. It can take a week to form the necessary biofilm. Second is that once the biofilm forms, there’s no guarantee that it will be viable and interact efficiently with the electrode surface.
Researchers in the Furst Lab have been able to chemically attach microbial fuel cells to electrode surfaces using what she calls “DNA Velcro.” "If we have DNA on an electrode and DNA on our cells, we can force these cells to adhere much faster than they would otherwise," she says. “And because DNA can act like a wire, we can get current much faster.”
The new sensors and technologies that Furst is developing have the potential to revolutionize industries from healthcare to clean energy, in applications on an industrial scale and in the home. “The emphasis that MIT puts on working on projects that are translatable is often not found in academic settings.” Furst says. “It's really exciting to be at a place that not only encourages that, but actively supports it.”