Electrochemical detection of natural DNA damage induced by ferritin/ascobic acid/H2O2 system and amplification of DNA damage by endonuclease Fpg

Oppositely charged natural DNA and chitosan (CS) were assembled into (CS/DNA)_n layer-by-layer films on electrode surface, and Ru(bpy)₃²⁺ (bpy = bipyridyl) in solution was used as electroactive catalyst to detect damage of DNA in the films after incubation of the films in ferritin/AA/H₂O₂ solutions (AA = ascorbic acid). The mechanism of DNA damage caused by the ferritin/AA/H₂O₂ system was similar to that of Fenton reaction, where the reaction of ferritin with AA would release some Fe(II) ions from ferritin and the following reaction between Fe(II) ions and H₂O₂ would produce hydroxyl radical, which could induce DNA oxidative damage. This system provided an in vitro model to imitate the DNA damage indirectly induced by ferritin in real bio-systems. In addition, formamidopyrimidine DNA glycosylase (Fpg), a key endonuclease enzyme in repair of oxidatively damaged DNA, was used to amplify the DNA damage caused by ferritin/AA/H₂O₂ system through conversion of oxidative purine bases into single-strand breaks. The high sensitivity of electrocatalytic method with Ru(bpy)₃²⁺ as the catalyst in detection of DNA damage and the magnification function of Fpg may provide a novel idea to detect natural DNA lesion sensitively.