It’s a frightening scenario: soldiers are deploying and there’s a threat to release poisonous gas. How would commanders know if there really was gas and how toxic it might be?
Narayan Bhattarai at North Carolina Agricultural and Technical State University (NC A&T) and Jeffrey Macdonald at the University of North Carolina – Chapel Hill are working on a system to test for organophosphate toxins. It would use human liver cells not only to detect a poison gas, but to tell how serious the dose is and the likely human effects.
The eventual goal is a small device that would work much as a glucose strip works to test blood sugar, said Macdonald, a regenerative medicine specialist. “Say you had a sarin attack or mustard gas attack, something like that – you could basically sample that air and then put it in a solution and test it on these cells,” Macdonald said. “Based on the metabolic profile, we could tell you it was a mustard gas in quick time.”
With the help of the Minority-Serving Institution STEM Research & Development Consortium (MSRDC), Bhattarai’s lab won a $248,566 Department of Defense grant to develop the test and came up with a way to encapsulate live liver cells in gel microspheres.
They managed to make a uniform array of these tiny balls of liver cells and float them in a standard 96-well lab plate. “We thought we could deploy this frozen mini-liver set-up in a battlefield, then collect a sample and immediately test it,” Bhattarai said. “That would tell us how much time it takes to clear, to metabolize in the liver.”
Macdonald thinks it can be simplified even further. If they can get the system up and running, they could test human liver cells against a range of toxic gases and liquids and come up with a color-based system to quickly tell a user what kind of toxin is present and how the human body is likely to respond to it. “We could develop a color-metric assay that you could use … almost like glucose strips,” he said.
In the meantime, the plan was to share the little mini-liver test plates. “We were going to try to freeze the liver cells and then send them out to (other labs) interested in testing them,” he said.
One reason for mixing the liver cells into a gel is to keep them from turning into a useless blob. “The problem with liver cells is if you don’t encapsulate them and put them in a dish, they bind to one another and they form a big ball of cells,” Macdonald said.
The gel can also help keep them alive so they don’t die when frozen and then thawed.
“If not properly frozen, they will die,” Bhattarai said.
But the funds ran out. “We never even got to the cool part. We got stuck on the freezing of the cells,” Macdonald said. “We were really starting to cook when the funding ended,” he added.
Since then, Bhattarai’s lab has developed a way to use biodegradable nanorods made from chitin taken from shrimp and crab shells. When mixed into the gel microspheres, they seem to help the liver cells survive better. “I think this fiber will increase oxygen transfer and provide mechanical support for the cell -- help it grow and function,” Bhattarai said.
Macdonald says his lab can get human liver cells from livers deemed unsuitable for transplant use. They are otherwise thrown away. “Now we are set up so that we could do better. We can look at what would happen in a real human being,” he said.