UC Novel Biosensor Detects Dangerous Water Toxins

As a native of Cyprus, Dionysios D. Dionysiou, University of Cincinnati environmental engineering professor in the College of Engineering and Applied Science, knows first-hand the value of water. The country of Cyprus, like many other arid islands, depends heavily on rainwater and on advanced technologies, like reverse osmosis, to purify water from the Mediterranean Sea. The need to secure enough clean potable water in arid countries and the developing world has led Dionysiou to devote his career to water quality and sanitation.

One particular problem of interest to Dionysiou particularly interested in the way common blue-green algae can poison water enough to potentially kill animals and humans. Cyanobacteria bacteria, also known as the blue-green algae, rapidly reproduce, forming algal blooms, which produce large enough quantities of cyanotoxins that they become poisonous and have the potential to kill animals and humans alike. These cyanotoxins exist in water all over the world, even in Ohio, particularly in lakes and ponds

Due to their overwhelming and harmful presence, developing sensors is crucial for the continuous monitoring of cyanotoxins in freshwater aquatic systems that serve as drinking-water sources. Dionysiou and his team of researchers collaborate with the best minds around the world, including other UC research groups (the Nano World and the research group of William Heineman, chemistry professor at McMicken College of Arts and Sciences), the U.S. Environmental Protection Agency and a research team from Greece’s National Center for Scientific Research (NCSR) in Demokritos. Together, they work to treat contaminated water, prevent such contamination and provide early warning in case of contamination.

Dionysiou and his team began their work studying the use of electrodes based on long nanotube (CNT) arrays. Carbon nanotubes are carbon atoms arranged in hexagonal patterns forming a tube that is nanoscale (one billionth of a meter or one hundred thousandth of the width of a human hair). The researchers discovered that when CNT arrays’ electrodes are combined with monoclonal antibodies (specific for each cyanotoxin), the nanotubes function as highly selective biosensors to detect cyanotoxins.

The teams’ research on monitoring such contaminants provides fundamental information to develop a highly selective, fast-responding biosensor prototype to detect these highly harmful toxins in water and develop early warning systems to protect public health.

Dionysiou explains further, “The increasing incidence of cyanobacteria harmful algal blooms (Cyano-HABs) in freshwater estuaries worldwide has become a growing concern among the scientific community. Ohio also has seen the problem in various surface waters including Ohio River, Lake Erie,and several smaller lakes in Ohio. The presence of harmful cyanotoxins from Cyano-HABs at high concentrations in sources of drinking water is a serious threat to the health of humans and wildlife.

"To protect the health of humans, there are two approaches: one is degrading the toxins and the other is monitoring the toxins in sources of drinking water. Developing highly selective and fast-responding sensors to monitor these toxins is one of the major challenges to assess the associated health risks. There is a lack of studies for rapid monitoring and quantification of cyanotoxins in sources of drinking water compared to other anthropogenic contaminants to be destructed and monitored. Therefore, there is an urgent need to develop innovative monitoring technologies for cyanotoxins in sources of drinking water supply."

To date, Dionysiou and his colleagues have completed the fundamental studies needed to develop biosensors for monitoring cyanotoxins, as well as established methods to fabricate biosensors using carbon nanotube arrays and specific antibodies. They plan to pursue more advanced studies to improve the specificity of the biosensors. Such studies can provide key knowledge to develop electrochemical biosensors for the monitoring and detecting of many different cyanotoxins as well as improve the selectivity and specificity of the sensors. Dionysiou hopes to eventually produce reusable biosensors for sustainability reasons. 

“I believe our future work will focus on comprehensive research to develop various smart sensors for the most important and frequently encountered cyanotoxins in freshwater aquatic systems, possibly marine environments," Dionysiou says. "We expect also to develop various types of nanosensors for other contaminants. A significant effort will also be devoted to various novel and effective treatment processes to purify water contaminated from such toxins in both engineered processes (like water treatment systems, small scale treatment systems) and in the aquatic systems. We would also like to pursue research on treating water better or understanding factors that can minimize the input of pollutants from non-point sources. We expect some of these efforts will be developed in collaboration with other scientists like ecologists, water treatment industry professional, municipalities, and other state and federal stakeholders.” 

Biosensors aren’t the only subject of interest for Dionysiou. He collaborates with faculty and students on numerous projects related to the removal of cyatontoxins.

Dionysiou elaborates, “Changseok Han, a doctoral student, is developing innovative photocatalysts (the acceleration of a photoreaction in the presence of a catalyst) to decompose cyanotoxins and contaminants of emerging concern.

"Xuexiang He, a doctoral student, performs research with a specific focus on water quality, treatment and supply. She applies UV, thermal and/or transition metal activation of hydrogen peroxide, persulfate and peroxymonosulfate for the removal of contaminants including cyanobacterial toxins, pharmaceuticals and antibiotics, from drinking water.

"Geshan Zhang, a doctoral student in environmental science, is focusing on a project about a visible light-activated polymorphic titanium dioxide photocatalyst and its photocatalytic activity for the destruction of contaminants including cyanotoxins. Zhang’s project is funded by the U.S. Department of Agriculture in collaboration with researchers from Florida International University and Central Metallurgical R&D Institute in Cairo, Egypt.

"Joel Andersen pursues his doctoral work revolving around visible light-activated titanium dioxide. More specifically, his investigations deal with determining the role of various reactive oxygen species created during photocatalysis of an emerging toxin known as microcystin-LR. He also seeks to correlate those roles with the observed intermediate degradation products.”

Through the profound devotion and research efforts of Dionysiou, his students, and their collaborators, water quality is improving not just within the area but around the planet. As they continue to collaborate with the best minds in the field, UC moves another step closer to correcting and preventing water-quality problems with a novel, highly selective and fast-responding biosensor.