Abstract
An electrochemical DNA biosensor based ona G-quadruplex (G4) forthe sensitive determination of Pb2+ was reported usinga carbon paste electrode (CPE) ora multi-walled carbon nanotube paste electrode (MWCNTPE) as working electrodes, ethyl green (EG) as a new G4 intercalator, anda single-stranded nucleic acid sequence rich in guanine (G) as DNA probe. Electrochemical determination of Pb2+ relied on probe structural changes from single - stranded to the stabilized intramolecular G4 in the presence of Pb2+, which caused a change in the current ofthe EG reduction peak due to the intercalation of EG into the G4 structure. The change inthe reduction peak of EG before and after its intercalation into the stabilized G4 (∆I) had a linear correlation to the concentration of Pb2+ ions. The linear ranges of 4.0×10-10-5.0×10-9M and 2×10-7-1×1-5M with a detection limit (LOD) of 1.04×10-10M were obtained using CPE, while improved linear ranges of 4.0×10-11-1.0×10-9M and 2×10-7-1×10-5M with a lower LOD of 2.64×10-11M were achieved using the MWCNTPE biosensor. The biosensors exhibited satisfactory results in terms of selectivity and practical applicability inthe analysis of real samples. Graphical abstract The principle of the electrochemical sensing of Pb2+ based on intramolecular G-quadruplex using EG.
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