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AU’s Alex Zestos Develops Sensor to Detect pH Changes in Body

Potential implications for the study of cancer, stomach ailments, and other diseases

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Alex Zestos and his student research team. Photo by Jeffrey Watts.

Alexander Zestos, a bioanalytical chemist and American University associate professor of chemistry, has constructed a novel carbon electrode pH sensor that can be implanted into tissue to measure fast pH changes in the brain. His research has been conducted in collaboration with the National Institute of Standards and Technology (NIST) and published in the Royal Society of Chemistry’s journal, Sensors and Diagnostics

“Carbon fiber microelectrode sensors and arrays allow for the measurement of multiple biomolecules and biomarkers in several brain regions simultaneously,” says Zestos. “This work could potentially correlate chemical changes in several regions to further help understand complex brain heterogeneity and the effects of several drugs, behaviors, and disease states. Adding a pH sensor application to this electrode could potentially expand its utility and provide further information during the measurement.”

The Many Roles of pH

Figure source: Analytical and Bioanalytical Chemistry, 2021, 413, 6715-6726.

In the human body, pH levels can affect digestion, metabolism, hormones, diseases, homeostasis, and more. Zestos’ new microelectrodes could be used to measure pH shifts in the brain, blood, and urine. For example, they could be used to measure pH in the stomach (which typically has a relatively low pH for digesting and absorbing foods) to help further understand the gut microbiome. 

Zestos’ carbon fiber pH sensor is unique because it is relatively small, biocompatible, and has a very fast response time. “Having a pH sensor that could measure pH in tissue could provide many advantages in making advances towards better diagnostics for human health,” he says. For example, it could have implications for identifying or treating stomach conditions such as irritable bowel syndrome and acid reflux. 

The sensors could also be a quick way for lab clinicians to distinguish “healthy” from “sick” tissue samples, Zestos explains. As cancerous pre-tumors and tumors grow, they consume great amounts of oxygen and have a lower pH state than healthy cells and tissues. The tiny sensors can be implanted in vivo in animal tissue to test the pH of healthy and cancerous cells. The measurements can be used by researchers, lab technicians, oncologists, and even pharmaceutical companies to understand how disease progresses and how to develop and test treatments. 

The sensors also show potential for researching other diseases such as Parkinson’s Disease. Understanding pH-dependent shifts in signal could help enhance dopamine detection, which is important for understanding many diseases states.


Micro-electrode diagram
Figure source: Sens. Diagn., 2022, 1, 460-464.

Tools for Providing New Insights into Brain

 Zestos’ research has contributed to a deeper understanding of disease, addiction, mental health, and electrode development. In 2019, he constructed a groundbreaking carbon fiber multi-electrode sensor that can be implanted into brain tissue to measure many neurotransmitters in multiple brain regions simultaneously. Up to that point, researchers had only been able to measure neurotransmitters in one part of the brain at a time using electrochemical techniques. Zestos used the sensors to measure key neurotransmitter levels, such as serotonin, norepinephrine, and dopamine. His work, funded by the National Science Foundation and the National Institutes of Health’s BRAIN Initiative, provided new insights into how the brain functions.

The sensor development project received a National Science Foundation I-Corps Program grant in 2019. Zestos was introduced to I-Corps the previous semester when he participated in AU’s National Science Foundation (NSF) Site Program. It was part of the university’s $250,000 NSF grant to guide researchers towards successful applications to its national program.

The I-Corps Program grants are also designed to help scientists extend their focus beyond university labs and move their work towards the development of real-world products to solve real-world problems. Zestos’ grant gave him the training and resources to build a team to conduct research, customer discovery, and business development. 

As Zestos finds new and novel ways to use the sensors for research, he is also working to take his arrays beyond the lab and into the open marketplace, where they have the potential to be marketed to scientists, physicians, and other researchers studying the brain, DNA, pH, disease and much more.