The NO(2)• radical is one kind of reactive nitrogen species and can be generated by horseradish peroxidase (HRP)-catalyzed oxidation of nitrite (NO(2)(-)) in the presence of hydrogen peroxide (H(2)O(2)) and may cause DNA damage in living system. In the present work, {PDDA/DNA}(4) layer-by-layer (LBL) films assembled with poly(diallyldimethylammonium chloride) (PDDA) and natural double-stranded DNA on electrodes were used to detect DNA damage induced by NO(2)• radicals generated from the HRP+H(2)O(2)+NO(2)(-) incubation system using cyclic voltammetry with Ru(bpy)(3)(2+) as the electroactive catalyst in solution. HRP and DNA were then further assembled into PDDA/DNA/{HRP/DNA}(2) LBL films, and the damage of DNA in the films caused by the NO(2)• radicals produced in situ by incubation of the films with H(2)O(2)+NO(2)(-) solutions was detected electrochemically. When catalase layers were assembled on the surface of PDDA/DNA/{HRP/DNA}(2) films, the DNA damage induced by the H(2)O(2)+NO(2)(-) system was inhibited since the catalase in the films could effectively decompose H(2)O(2), and the NO(2)• radicals could not be generated. This work not only provides a foundation for fabricating electrochemical biosensors in detecting NO(2)•-induced DNA damage, but also offers an in vitro model to simulate the pathway of DNA damage and protection in living process.
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