In the controlled doses found in toothpaste and many municipal water supplies, fluoride contributes to dental The assay turns the water yellow after two hours if elevated fluoride concentrations are present. Source: Northwestern Universityand bone health. However, exposure to excess waterborne concentrations that occur naturally in some regions can cause skeletal fluorosis. A simple biosensor has been engineered at Northwestern University for use by anyone in the field to detect potentially dangerous levels of fluoride in drinking water.

The inexpensive detector takes its cue from the bacterial reaction to fluoride, which is to rely on RNA to sense toxic levels and initiate a detoxification process. The researchers freeze-dried this RNA reaction, stored it in a test tube and used a pipette to draw just 20 micoliters of water from the source being tested. The rehydrated RNA will turn the water yellow after two hours if elevated fluoride concentrations are present.

The method was demonstrated to detect fluoride at levels above 2 parts per million, the U.S. Environmental Protection Agency’s most stringent regulatory standard, in both laboratory and field conditions. The researchers will next explore different types of engineered RNA to test for other potentially harmful substances.