Detection Methods Of8-hydroxy-2’-deoxyguanosine Based On Aptamer Conformation Switching

The formation of8-hydroxy-2’-deoxyguanosine （8-OHdG） reflects oxidativeDNA damage by oxidative stress, mainly by hydroxyl radicals. This DNA damagecauses specific types of mutation and mispairing of base. Its increase has been seen inaging, cancer and exposure to different toxic agents.8-OHdG is a principal stablebiomarker of oxidative damage of DNA. Quantitative analysis of8-OHdG in bodyhas a great significance to the study of carcinogenesis and mechanism of aging.In the chapter2, a sensitive, highly specific and low cost method of visualcolorimetry for the determination of8-hydroxy-2’-deoxyguanosine （8-OHdG） inhuman urine was developed using unmodified gold nanoparticles （AuNPs） as probes.In the presence of8-OHdG, the conformational change of8-OHdG-aptamer from arandom coil structure to G-quardruplex structure results in a color change of thesystem. The response signals linearly correlated with the concentration of8-OHdGover the ranges of5.60×10^-92.82×10^-7mol·L^-1, and the limit of detection（LOD） is1.68×10^-9mol·L^-1. The relative standard deviation and the recovery were1.12⁴.19%（n=6） and95.9¹04.9%, respectively. The proposed method avoidsthe label and derivatization steps in common methods, and allows direct analysis ofthe samples by the naked eyes without costly instruments, and was reliable,inexpensive and sensitive.In the chapter3, we develop a simple resonance light scattering method for thedetermination of urinary8-OHdG. The present method is based on the fact that in thehigh-salt solution, the interaction of8-OHdG with aptamer results in the RLS increaseof AuNPs. A linear correlation existed between RLS change （ΔI） and theconcentration of8-OHdG in the range of9.08×10^-111.412×10^-8mol·L^-1. Theequation of linear regression is ΔIRLS=10.7+12.7c (×10^-9mol·L^-1), and the limit of detection （LOD） is2.73×10^-11mol·L^-1. The relative standard deviations were1.63%³.46%（n=6）. The proposed method has been used for the actual sample testing, andthe results are satisfied.In the chapter4, a new method was developed for the determination of urinary8-hydroxy-2’-deoxyguanosine using gold nanoparticles by spectrophotometry. In theBritton–Robinson buffer solution of pH3.5,8-hydroxy-2’-deoxyguanosine （8-OHdG）combined with gold nanoparticles, resulting in the absorbance change of the solution.A linear correlation existed between the absorbance change [Δ（A630/A520）] and theconcentration of8-OHdG in the range of4.98×10^-7mol·L^-11.27×10-5mol·L^-1. Theequation of linear regression is Δ(A₆₃₀/A₅₂₀)=–0.00713+0.0812c (×10^-6mol·L^-1) witha correlation coefficient （r） of0.9984. The detection limit （LOD） is1.50×10^-7mol·L^-1.The relative standard deviations were1.48%³.57%, and the recovery was96.1%⁹8.0%. The proposed method was simple, rapid and cheap.