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

A now injection analysis system coupled with an evanescent wave biosen sor 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 a s the reference compound for the detection. The evanescent wave biosen sor 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 unmo dified fiber. The response of the biosensor at a constant concentratio n of ethidium bromide increases on increasing the concentration of imm obilized dsDNA. At the steady-state response of the biosensor, obtaine d at a constant concentration of ethidium bromide, there is a decrease in the response to the injection of another DNA intercalator that com petes for the intercalation sites on the dsDNA, displacing the ethidiu m bromide. This is immediately followed by recovery of the steady-stat e response. The decrease in the sensor response is a linear function o f the concentrations of injected intercalator. Response curves for 9,1 0-anthraquinone-2,6-disulfonic acid, remazol brillant blue, decacyclen e, and 4',6-diamidino-2-phenylindole dihydrochloride are reported.