Fluorescent signature

By Priyanka Chandola
Published: Monday 31 August 2009

A solution that detects minute presence of ozone, even in cells

ozone in the stratosphere protects the earth from harmful ultraviolet rays. But when in the troposphere, near the ground level, it acts as a pollutant. Though it is not emitted directly, emissions from car engines or industrial operations react to form ozone. Inhaling it can irritate the respiratory system, worsen bronchitis and asthma, and harm heart and lung functions.

Scientists from the University of Pittsburgh, the US, have developed a method that can help detect ozone even in minute level--be it in air or in body cells such as lung cells.

The method consists of a molecule of homoallyl ether in a solution of acetone and water. When ozone is bubbled through the solution, a fluorescent compound is obtained. The compound glows bright green when exposed to laser or ultraviolet rays, said Kazunori Koide, professor of chemistry at the university. He is the lead researcher. "We used instruments such as spectrofluorometer (instrument that provides information on the properties of fluorescent compounds) and microscope for our research. But any source of laser can reveal the colour," said Bruce R Pitt, professor of environmental and occupational health, also part of the research.

To detect ozone in the ambient air, the scientists placed the solution in an outdoor area in Pittsburgh with heavy vehicular traffic for eight hours. It successfully detected ozone. For indoor experiment, they coated paper strips with the solution and placed them in a non-ventilated office with two photocopiers and laser printers--devices known to generate ozone. After eight hours, when exposed to ultraviolet light, they revealed ozone. Unlike other ozone-detection methods, which fail to give accurate information because the chemicals used react with other compounds, the method is ozone specific. The scientists envisage the method can be used to develop a badge for patients with respiratory problems so that they can measure their exposure to ozone.

Though inhaling ozone is known to damage tissue linings of the lungs, there have been doubts if ozone can penetrate cells. The probe offers a clue to it.

The scientists used the method to examine the presence of ozone in airway liquid lining. "Human airway liquid is the first major interface in which environmental ozone comes in contact with individual tissue," said Pitt. The solution produced a strong fluorescence signal. Human lung cells, treated with the solution, when exposed to ozone-rich air for five minutes, the glow expanded within the cell, the scientists noted in the July issue of Nature Chemistry. This suggests ozone has some penetrability.

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