DETECTION OF AROMATIC-COMPOUNDS BASED ON DNA INTERCALATION USING AN EVANESCENT-WAVE BIOSENSOR

A now injection analysis system coupled with an evanescent wave biosensor employing total internal reflection of fluorescence radiation for the detection of the compounds that intercalate within DNA is reported. A highly fluorescent intercalator, ethidium bromide, has been used as the reference compound for the detection. The evanescent wave biosensor was developed using immobilized double-strand DNA (dsDNA) over the surface of a cylindrical wave guide. The response of the DNA-modified fiber is significantly higher than the response obtained with an unmodified fiber. The response of the biosensor at a constant concentration of ethidium bromide increases on increasing the concentration of immobilized dsDNA. At the steady-state response of the biosensor, obtained at a constant concentration of ethidium bromide, there is a decrease in the response to the injection of another DNA intercalator that competes for the intercalation sites on the dsDNA, displacing the ethidium bromide. This is immediately followed by recovery of the steady-state response. The decrease in the sensor response is a linear function of the concentrations of injected intercalator. Response curves for 9,10-anthraquinone-2,6-disulfonic acid, remazol brillant blue, decacyclene, and 4',6-diamidino-2-phenylindole dihydrochloride are reported.