Title of Post: Sensing Potassium
Authors: Xianfeng Zhou, Fengyu Su, Yanqing Tian, Cody Youngbull, Roger H. Johnson, and Deirdre R. Meldrum
Journal: Journal of the American Chemical Society
Affiliation: Center for Biosignatures Discovery Automation, Biodesign Institute, Arizona State University
Potassium is a critical part of many biological functions and changes in concentration of potassium ion in the body is an indicator of a variety of diseases. In this paper the authors develop a new sensor to detect K+ using confocal fluorescence microscopy. Confocal microscopy is a type of microscopy that uses special instrumentation to create extremely high resolution optical images. Combined with fluorescent probes, confocal microscopy allows one to precisely track groups of fluorescing molecules.
The authors combined an electron-withdrawing group, 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran, with an electron-donating group based on a triazacryptand ligand, that has been used previously in K+ sensors, to create a red-fluorescent K+ sensor. Their new sensor, KS2, has an absorption maximum at 560 nm and has weak fluorescence when K+ is not bound. When potassium ion, in concentrations of 140 and 1400 mM, was introduced, fluorescence increased 4 to 50 times, respectively. These concentrations are similar to concentrations found in various types of cells in the human body.
The authors also investigated how selective the sensor was to K+. They introduced K+, Na+, Ca2+, Mg2+, Fe3+, Zn2+, Mn2+, and Cu2+ to the sensor. The researchers found that the highest response was from potassium ion. They also found that sensitivity to K+ was not affected by pH in the range between 5 and 8.
The authors also investigated the cytotoxicity of KS2 to human glioblastoma U87MG cells. After the sensor was in the cells for 2 hours over 97% of the cells were still viable. During this experiment they were also able to determine that KS2 was able to get in the cells within 10 minutes of exposure.
In this paper the researchers demonstrate a new red-fluorescent chemsensor that allows for the detection of potassium ion at a variety of concentrations which has the potential to be useful in a variety of biological applications.