Electrochemical Researches Of DNA Damage Induced By Ferric Ions Catalyzed Oxidation Of Catechols

DNA is the basis material of organism, and it plays a vital role in our body. The integrity of DNA is essential for cell or organism. Extensive observations suggest that DNA damage accumulates with age and that this may be due to an increase in production of reactive oxygen species and a decline in DNA repair capacity with age. Many biological diseases, such as Parkinson’s disease, tumour or cancer, have a close relationship with free radicals immediate-damage to DNA. It is quite necessary and important for investigating the mechanism of damage processes induced by unstable active specie.As a new green class of nonaqueous solvents, ionic liquids (IL) possess a series of unique advantages:an excellent ionic conductivity, wide potential window, a good chemical and thermal stability, modified the property through the design of anion and cation ion in order to satisfy various system. In the field of electroanalysis, the applications of IL generally focus on as an alternative solvents or supporting electrolyte, and the electrode modified material in application of biosensors and biocatalysis. Further more, IL has greater viscosity, so the diffusion process of free radicals in the ionic liquid system is slow. It reduces the chances of collision with each other, thus extending their life. It provides more appropriate environment than traditional aqueous solution for the study of free radicals.The main contents and results are summarized as follows:(1) Electrochemical methods were utilized to investigate dopamine/Fe3+reaction induced DNA damage in aqueous solution. DNA film modified electrode has been constructed on the glassy carbon electrode surface by the direct adsorption technique. An electroactive and sensitive indicator [Co(bpy)3]3+, which bonded to the intact DNA much more than the damaged DNA, was employed in the detection of DNA damage by differential pulse voltammetry. It was a symbol of DNA damage that the peak current of the [Co(bpy)3]3+decreased. Meanwhile the degree of DNA damage generated in this cleavage agent is ca.6-fold severer than that of Fenton system. The most likely mechanism of DNA damage induced by dopamine/Fe3+reaction was that the·OH generated from the ferric ions facilitated oxidation of dopamine disturbed DNA double helix structure or caused DNA strand break. The formed hydroxyl radical (·OH), as the substaintial cause of DNA damage, was validated by Ultraviolet-visiable spectroscopy. Electrochemical impedance spectroscopy was also used for verifying that DNA charge transport was attenuated during the process of DNA damage with the universal index of the charge-transter resistance. The optimizations of incubation time and dopamine/Fe3+molar ratio on DNA damage were explored. Moreover, the experimental results testified that both ascorbic acid and rutin could protect DNA from oxidative damage efficiently. The methods were promising for rapid, sensitive, and inexpensive detection of DNA damage.(2) DNA damage caused by dopamine/Fe3+system can be monitored electrochemically by the means of combining DNA directly adsorbed electrodes and electroactive probe of [Co(bpy)3]3+in RTIL system. Based on the property of large viscosity,[bmim][BF6] could let the speed of radical travel down, reduce the chance of interactive collision among radicals and prolong the lifetime of radicals, then provide much more appropriate environment for the generation of·OH and the investigation of DNA damage than aqueous solution. Meanwhile the degree of DNA damage generated in this cleavage agent is more severe than that in Fenton system. The possible DNA damage principle in our work was that the hydroxyl radical generated through the ferric ions facilitated oxidation of dopamine disturbed DNA double helix structure or caused DNA strand break, leading to the decrease of signal respond. Electrochemical impedance spectroscopy was also used for verifying that DNA charge transport was attenuated during the process of DNA damage. The fabricated sensor exhibited excellent stability and reproducibility.(3) The cleavage reagents (Fe+and catechol) in aqueous solution mediated oxidative damage to DNA were investigated. The generation of hydroxyl radical was validated by ultraviolet-visible (UV-vis) spectroscopy. The electroactive indicator [Co(bpy)3]3+was employed for the detection of DNA damage by DPV. The decrease of oxidation signals was used for the symbol of DNA damage. The possible DNA damage principle in this work was that the hydroxyl radical generated through the ferric ions facilitated oxidation of catechol disturbed DNA double helix structure or caused DNA strand break, leading to the decrease of signal respond. Electrochemical impedance spectroscopy was also used for verifying that DNA charge transport was attenuated during the process of DNA damage. The optimizations of incubation time and catechol/Fe3+molar ratio on DNA damage were explored. A certain range of concentration of AA and rutin represent an efficient antioxidant effect on protecting DNA from oxidative damage. The fabricated sensor provided a stable and sensitive platform for the monitor of DNA damage.