Detecting marine pollutants with an antibody-based sensor

Researchers combine biology and technology to develop an instrument for detecting hazards in our waters.

In a development that combines biology with technology, researchers at the Virginia Institute of Marine Science have created a biosensor that uses antibodies to detect marine pollutants. The biosensor could be used to monitor for oil leaks and other hazards, said the institute's Michael Unger in a recent interview. Below are excerpts from our discussion.

What does it mean to have an antibody-based sensor?

Antibodies normally recognize fairly large macro-molecules. They typically don't recognize very small molecules like we're interested in detecting with the bio-sensor. We produce an analog of our contaminant of interest and attach it to a protein. [We] immunize a mouse [and] the mouse produces antibodies to this protein with the contaminant coating on the outside of it. The antibodies have pockets that bind the free contaminant. Once the mouse has produced antibodies, we can isolate the cells that produced those antibodies in culture and produce an unlimited supply.

The antibodies [can be used] as a reagent in an instrument. Once they're in solution and we mix them with the sample of concern, the antibodies will bind the free contaminant. The degree of binding of that contaminant gives us a response in the instrument. We not only detect the contaminant, but also get a quantitative measurement of it. On this antibody, we have a fluorescent tag. Our instrument measures fluorescents. But the specificity of the instrument comes from the antibody that is binding the contaminants in the solution. It's a unique way to use antibodies as an analytical tool.

Had this method been used before?

We did not invent the hardware. We worked with the company Sapidyne Instruments, which has this type of instrumentation commercially available. The key is having the antibody that recognizes what you want to measure in the environment. Our group developed the antibodies to look in particular at polycyclic aromatic hydrocarbons (PAHs), which are the more prevalent water soluble components from oil and creosote. These are the chemicals of concern in an oil spill.

In our case in the Elizabeth River, there have been spills of creosote, which has high concentrations of PAH. They're what we're measuring with the antibodies we've produced in this instrument. It's very sensitive. It can detect down to parts per billion concentrations, which is necessary for environmental monitoring. And it's rapid. We can get results in a few minutes.

Did your work improve on the hardware or was your primary advancement the antibodies?

We had a collaboration with the company. Candace Spier, our graduate student, was the first author on the paper. This is part of her dissertation research. In the process of developing the sensor for the PAHs, she worked with the company and they made upgrades to the software. There was a lot of collaboration with the company in further development of the instrumentation to make it a better operating tool for the chemical analysis we were doing.

You mentioned the sensor can detect oil. What about other contaminants?

The paper coming out now is for polycyclic aromatic hydrocarbons and those are compounds released in an oil spill. Oil is a complex mixture of many chemicals. The polycyclic aromatic hydrocarbons are in the water-soluble fraction, which is what we're measuring with the instrument. It would work well for detecting the presence of oil.

With other antibodies, this technology could be adapted to look at a multitude of contaminants. We've developed another antibody that works well for TNT. TNT is from an explosive. It's a contaminant of concern on of defense bases because it has ended up in the ground or groundwater. The key is developing antibodies that specifically recognize the contaminants of concern.

Is that how you're continuing this work, by working on other antibodies?

Potentially, yes. This was a collaboration. I'm an environmental chemist. Steve Kaattari is an immunologist. His lab was instrumental in developing the antibodies. Part of what we're interested in now is using it. I'm excited about us having a tool to get these concentrations measured in near real time. Before, it took a lot of money and a lot of time to get single data points. Now we can look at how concentrations of these contaminants change in space and time. It enables us to do research that was expensive in the past. For instance, we could look for the presence of oil in environments. We're looking for sources, tracing the concentrations. There are multiple applications for this technology. We're interested in potentially developing the antibodies to look for new contaminants, as well.

Talk about your testing of the instrument in the Elizabeth River.

That was a particularly interesting application. We worked in collaboration with the Elizabeth River Project and the Elizabeth River Trust, which was involved in one of the first sediment remediation efforts in Virginia. The sediments there are contaminated with creosote from historical spills and the group is involved in dredging up the most contaminated areas. One of the concerns was whether the compounds, during the dredging process, would be released into the water column.

This enabled us to go to the site while they were initiating the dredging and monitor the PAH concentrations in the water column. We were able to document that the concentrations stayed low. During the project, they had a sediment curtain around the dredging area as an effort to control the release of the PAHs. We were wondering if that would be effective in reducing the PAH concentrations downstream from the site. We were able to operate the instrument in a boat, collect samples and within a few minutes produce data on the concentration of the PAHs. We called the engineers on the shore and notified them.

How else could the instrument be used?

Another example was to look at these compounds in storm water runoff. It's a concern that polycyclic aromatic hydrocarbons from exhaust and oil could end up in our water bodies. We collected samples at two water bodies that receive runoff from road areas. We were able to demonstrate that by sampling at the beginning of a rainfall, we could document the increasing concentrations of the PAHs in the receiving waters. This involved collecting and analyzing about 80 or 90 samples in a few hours. We were able to document, with a fine degree of resolution, the contaminant runoff in the storm water receiving waters.

Photo, top: Michael Unger

Photo, bottom: Candace Spier

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