Using exonuclease III to enhance electrochemical detection of natural DNA damage in layered films

The natural double-stranded DNA (dsDNA) was immobilized on electrode surface by layer-by-layer assembly, forming PSS/PDDA/dsDNA films (PSS, poly(styrene-sulfonate); PDDA, poly(diallyldimethylammonium)), and used to detect DNA damage electrochemically. The DNA lesion induced by the alkylating agent methyl methanesulfonate (MMS) could be detected by cyclic voltammetry with ruthenium(II) tris(2,2′-bipyridyl) (Ru(bpy)32+) in solution. After treated by E. coli exonuclease III enzyme, the electrocatalytic oxidation peak of the films was further amplified and greatly enhanced because the enzyme could convert those apurinic sites caused by MMS in the damaged dsDNA into single-stranded DNA regions and make more guanines in the DNA become exposed. This approach provided a novel idea for constructing DNA biosensor in sensitive screening of genetoxic chemicals in vitro.