A novel fluorescence aptasensor for 8-hydroxy-2′-deoxyguanosine based on the conformational switching of K+-stabilized G-quadruplex

A sensitive, lable-free and low cost fluorescence aptasensor was developed for detecting 8-hydroxy-2′-deoxyguanosine (8-OHdG) by using 8-OHdG aptamer (Apt) as a recognition probe and N-methyl mesoporphyrin IX (NMM) as a reporter. The method is based on the conformational switching of a K + -stabilized G-quadruplex to a 8-OHdG-stabilized one. NMM can selectively bind to K + -stabilized G-quadruplex instead of 8-OHdG-stabilized one. The addition of 8-OHdG in the solution of Apt - K + ions leads to a sharp change in fluorescence intensity, which showed a good linear response toward 8-OHdG concentration ranging from 3.96   nM to 211   nM with a detection limit of 1.19   nM. The relative standard deviation and the recovery were 1.23–3.26% ( n   =   11) and 94.8–106.7%, respectively. The proposed aptasensor consists of only an aptamer probe and a specific dye NMM, avoiding the complex and expensive labeling procedure. Thus it is much cheaper and more applicable.