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Biological Chemistry

Custom Lanthanide Probes

ACS Meeting News: Tailoring strategy permits tracking of diverse analytes

by Carmen Drahl
March 26, 2012

Borbas’ caged lanthanide probes detect a variety of analytes.
A reaction mechanism showing how the lanthanide probe detects an analyte.
Borbas’ caged lanthanide probes detect a variety of analytes.

New adjustments to luminescent probes made with lanthanide elements make it possible for the probes to detect two analytes in parallel. The work that led to that advance, presented on Sunday in the Division of Organic Chemistry at the American Chemical Society national meeting in San Diego, could also pave the way for regular use of lanthanide probes for imaging in live animals.

Probes featuring the lanthanides europium and terbium are already a fixture in labs for detecting biochemical entities such as citrate, lactate, and nitric oxide. Current routes to these probes, however, are either tedious or tough to adapt for detecting new analytes. In San Diego, graduate student Elias Pershagen and professor K. Eszter Borbas from Stockholm University, in Sweden, reported a customizable probe-making strategy (J. Am. Chem. Soc., DOI: 10.1021/ja3004045).

Lanthanide probes typically possess a light-harvesting antenna molecule. To make adaptable probes, Pershagen, Borbas, and colleagues decided to place a cage around the antenna that could be removed, switching the antenna on, only by a specific analyte. They chose a caged coumarin, which other groups have used for different light-harvesting applications. “There are dozens of antennae out there,” Borbas told C&EN. Coumarins are special, she said, because they’re easy to work with from a synthesis standpoint, have excitation wavelengths long enough to prevent damage to biomolecules, and uncage under mild conditions.

With their tailoring strategy, Borbas’ team made lanthanide probes for ions, small molecules, and enzyme activity. They simultaneously detected two analytes in solution by varying their probes’ caging group—from a boronic acid to pick up hydrogen peroxide, to a silyl group to detect fluoride.

Her team is trying to improve the probes’ emission efficiency by bringing the antenna closer to the lanthanide. They’re also exploring coumarins’ talent for two-photon absorption, which in theory could lead to probes that absorb at wavelengths that would make animal imaging more routine. “I would love to come up with a design that is even broader,” Borbas said, because the current probes are likely suitable for monitoring only hydrolases and oxidoreductases, not other enzyme classes.

“I think Dr. Borbas will take this clever, modular technology far,” said Kate Carroll, who develops probes to monitor redox biochemistry at Scripps Florida.

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