Electrochemical Investigation of Heterogeneous Affinity Behaviour of Methylene Blue and G‐quadruplex

Abstract

The heterogeneous binding behaviour between methylene blue (MB) and G‐quadruplex, one kind of single‐stranded (ss) DNA with specific guanine tetrads, has been thoroughly studied via electrochemical techniques. Positively charged MB interacted electrostatically with both G‐quadruplex and normal ssDNA but the binding and dissociation kinetics between them were significantly different. Compared with ssDNA, G‐quadruplex had a slower binding rate constant and dissociation rate constant with MB since there existed other different binding mechanisms between G‐quadruplex and MB besides electrostatic interaction. This work might provide valuable information in the design and development of DNA sensors.

A Homogeneous Label-Free Electrochemical microRNA Biosensor Coupling With G-Triplex/Methylene Blue Complex and λ-Exonuclease-Assisted Recycling Amplification

“…For example, the hemin/G4, a known horseradish peroxidase mimicking DNAzyme, has been widely used in the construction of various electrochemical biosensors ( Wu et al, 2017 ; Liu et al, 2017b ; Chen et al, 2018 ; Sun et al, 2018 ; Ji et al, 2019 ; Wu et al, 2021a ). The discovery that the combination of G4 and MB can cause a great reduction in MB diffusion current has further expanded its biosensing application scope ( Zhang et al, 2014 ; Cao et al, 2017 ; Zhao et al, 2020b ). Subsequently, it was found that G-triplex (G3), as a folding intermediate of G4, has an even stronger affinity to MB than G4.…”

“…Furthermore, molecular dynamics simulations indicated that intercalation was the major mode of interaction between G3 and MB ( Zhao et al, 2019 ). Since the first report, the G3/MB composite has been proved to be an universal, simple, sensitive and efficient homogeneous signal readout element for electrochemical biosensors ( Zhao et al, 2020a ; Chen et al, 2021 ).…”