Study On The Optical Sensing Methods For8-hydroxy-2’-deoxyguanosine Based On An Aptamer

8-Hydroxy-2’-deoxyguanosine (8-OHdG), as a product of DNA oxidativedamage, is formed in oxidative stress reaction when DNA is attacked by hydroxylradicals.8-OHdG can induce genetic mutation, base pair mismatch and so on.Correlational studies show that8-OHdG is closely related to many kinds of cancerdiseases and environmental pollution, and has been endorsed by international sciencecommunity as a biomarker for DNA oxidative damage. Therefore, establishing ahighly-specific, sensitive and convenient8-OHdG detection method is of greatsignificance for environmental monitoring, cancer research, etc.A highly-specific and sensitive colorimetric sensing method has been establishedin chapter two of this paper. A stable G-quadruplex based aptamer has been formedthrough conformational transformation due to the binding between8-OHdG and itsspecific aptamer, of which the process shows colorimetric response in hemin-ABTS2--H2O2system. Good linear correlation exists when the concentration of8-OHdGranges from466pM to247nM. The detection limit is140pmol/L, relative standarddeviation (RSD) ranges from1.23to3.26%(n=11) and the recoveries range from95.8to106.5%. Due to its economical, highly specific and sensitive features andadvantages of direct analysis by bare eyes and non-label usage, this method haspresented satisfying results for trace amount8-OHdG detection in human urinesamples.A novel Apt-NMM-8-OHdG system for detecting8-OHdG has been establishedin chapter3of this paper.8-OHdG can bind with the specific Apt in K+solutions,resulting in the formation of G-quadruplex, thus the fluorescence intensity of NMMwith faint fluorescent characteristics can be intensified through its binding withG-quadruplex. With the addition of8-OHdG, the G-quadruplex becomes morecompact and the binding strength of8-OHdG-Apt is stronger than that of G-quadruplex with NMM. Therefore, NMM is detached from G-quadruplex, whichleads to the decrease of fluorescence intensity. The difference in the fluorescenceintensities△F before and after the addition of8-OHdG has shown great linearrelationship with the concentration of8-OHdG. Thus, a new method based on thefluorescence quenching of8-OHdG has been established. The specific fluorescenceemission peak was located at610nm under optimum experimental conditions. Thefluorescence intensity linearly correlated with8-OHdG concentration ranging from3.96×109mol/L to2.11×107mol/L. The equation of linear regression is△F=34.1+47.9c (×107mol/L) and detection limit is1.19×109mol/L. The relativestandard deviation (RSD) ranges from1.23to3.26%(n=11) and the recoveries rangefrom94.8to106.7%. This method has been applied for the detection of8-OHdG inactual urine samples with the satisfactory results.