Detection of DNA damage induced by chromium/glutathione/H2O2 system at MWCNTs–poly(diallyldimethylammonium chloride) modified pencil graphite electrode using methylene blue as an electroactive probe

A new electrochemical biosensor for direct detection of DNA damage is presented by chromium/glutathione/H2O2 system using methylene blue (MB) as an electroactive probe. In this work, MWCNTs modified poly(diallyldimethylammonium chloride), MWCNTs–PDDA, nanoparticles were prepared. Then, a pencil graphite electrode (PGE) was modified with MWCNTs–PDDA nanoparticles. Finally, a double strain DNA (ds-DNA) was assembled on the surface of the modified electrode. To detect the DNA damage, the modified electrode was immersed into MB solution to load the MB into the ds-DNA presents on the surface of electrode. Differential pulse voltammogram (DPV) of the loaded MB on the electrode showed a sharp peak at −0.230 V vs. Ag/AgCl. In a blank solution, the MB loaded into the films was released gradually from the electrode surface, but the complete reloading of MB into the films could be realized by immersing the electrode into MB solution again, indicating the good reversibility of MB incorporation. However, after incubation of the DNA-modified electrode in the solution of known genotoxic agent (glutathione, chromium(VI) plus hydrogen peroxide), the damaged MWCNTs/PDDA/ds-DNA films could not return to their original form and fully loaded state with reloading of MB, thereby showing smaller DPV peak current.