Label-free fluorescent and electrochemical biosensors based on defective G-quadruplexes.

Abnormal levels of guanine closely associated with plenty of diseases are usually used as a biomarker for clinical diagnosis. In order to detect guanine and its derivatives accurately, in this paper, a defective G-quadruplex (DGQ) containing a G-vacancy at one of its G-quartet layers, and two kinds of G-quadruplex specific indicators including thioflavine T (ThT) and hemin were used for constructing a fluorescent and an electrochemical biosensor, respectively. In brief, a G-rich DNA probe is designed to form either hairpin or DGQ structure.

A ratiometric electrochemical biosensor for the exosomal microRNAs detection based on bipedal DNA walkers propelled by locked nucleic acid modified toehold mediate strand displacement reaction.

Sensitive and selective detection of microRNAs (miRNAs) in cancer cells derived exosomes have attracted rapidly growing interest owing to their potential in diagnostic and prognostic applications. Here, we design a ratiometric electrochemical biosensor based on bipedal DNA walkers for the attomolar detection of exosomal miR-21. In the presence of miR-21, DNA walkers are activated to walk continuously along DNA tracks, resulting in conformational changes as well as considerable increases of the signal ratio produced by target-respond and target-independent reporters.