Science

Frog skin provides crab-friendly alternative for detecting bacteria

Frog skin provides crab-friend...
Princeton engineers Michael McAlpine and Manu Mannoor with a frog peptide chip (Photo: Frank Wojciechowski)
Princeton engineers Michael McAlpine and Manu Mannoor with a frog peptide chip (Photo: Frank Wojciechowski)
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Princeton engineers Michael McAlpine and Manu Mannoor with a frog peptide chip (Photo: Frank Wojciechowski)
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Princeton engineers Michael McAlpine and Manu Mannoor with a frog peptide chip (Photo: Frank Wojciechowski)
The red knot, which eats horseshoe crab eggs
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The red knot, which eats horseshoe crab eggs
The frog peptide chip in use (Photo: Frank Wojciechowski)
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The frog peptide chip in use (Photo: Frank Wojciechowski)
Horseshoe crabs and African clawed frogs have both evolved systems off fighting off bacteria
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Horseshoe crabs and African clawed frogs have both evolved systems off fighting off bacteria
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Confused by that headline? It's simple really – when drugs and medical devices are tested for contamination, a substance called Limulus amebocyte lysate (LAL) is used. LAL is made from the blood cells of horseshoe crabs, which are caught along the U.S. Atlantic coast, drained of 30 percent of their blood, then returned to the water. Although the majority of the crabs survive the process, it has been estimated that at least 30 percent do not. This, in turn, is affecting populations of the red knot, a bird that feeds on horseshoe crab eggs. Now, engineers from Princeton University have discovered that a substance from the skin of the African clawed frog could be used instead of the crab blood – with no harm done to the frog. No word on whether eye of newt or wing of bat would work, too.

Horseshoe crabs are used because their immune system has evolved to produce amebocytes, antimicrobial blood cells that fight off the bacteria that are plentiful in the crabs’ seabed environment. When a drug or device sample is added to a solution of LAL, which is made from the amebocytes, the solution will turn to gel if the sample is contaminated.

Horseshoe crabs and African clawed frogs have both evolved systems off fighting off bacteria
Horseshoe crabs and African clawed frogs have both evolved systems off fighting off bacteria

Like the crabs, the frogs also have an antibacterial defense system. They produce peptides (small chains of amino acids) on their skin, to protect against infections. The Princeton engineers have discovered a method of attaching these peptides to a small electronic chip, that emits a signal when exposed to bacteria such as E. coli and salmonella. The African frogs, which are common in laboratories and pet stores, are not harmed in the process, and the peptides can be synthesized.

The frog peptide chip in use (Photo: Frank Wojciechowski)
The frog peptide chip in use (Photo: Frank Wojciechowski)

“It's a robust, simple platform,” said lead researcher Michael McAlpine. “We think these chips could replace the current method of testing medical devices and drugs.”

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1 comment
Michael Mantion
HELP... I am confused. If you drain a crab of 30% of its blood and it has a 30% chance off death. Why not just drain all the blood, and catch 70% fewer crabs. then use the drained crabs as Fish bait. If the red knots need the crab eggs, only harvest blood from the male crabs if possible. I assume like most crabs their gender can be determined readily on the crab boat.