Electrochemical Sensor for the Simultaneous Detection of Guanine and Adenine Based on a PPyox/MWNTs-MoS2 Modified Electrode

Guanine (G) and adenine (A) are two important components of nucleic acid and some small molecules in an organism. In this paper, we developed a new and convenient biosensor for the simultaneous determination of G and A based on overoxidized polypyrrole/multi- walled carbon nanotube and molybdenum disulfide modified glassy carbon electrode (PPyox/ MWNTs-MoS2/GCE). The composite material exhibited remarkable electro-catalytic properties toward the oxidation of G and A due to its large surface area and fast electron transfer. The oxidation peak positions of G and A were at 0.73 V and 1.03 V, respectively, which allowed simultaneous detection of the two substances in coexistence solution. The designed biosensor exhibited linear responses to G and A both in the ranges 5–30 μM and 30–120 μM, with detection limits (S/N = 3) of 1.6 μM (G) and 1.7 μM (A), respectively. Moreover, interferences from some coexisting electro-active species including inorganic ions, glucose, glycine and citric acid were nearly negligible. Further, the sensing strategy was successfully used for the detection of G and A in real samples with satisfactory results, indicating a potential application for the simultaneous electrochemical detection of G and A.