Novel electrochemical biosensing platform for microRNA detection based on G-quadruplex formation in nanochannels

Abstract Ultrasensitive detection of microRNA is crucial important in the diagnosis of related diseases. By immobilizing the capture probes in nanochannels, we developed a label-free electrochemical biosensing platform based on guanine-quadruplex (G-quadruplex) formation in nanochannels. The designed capture probe contains both the microRNA-21 (MiR-21) recognition sequence and guanine-rich sequence. The presence of the target MiR-21 would trigger the enzymatic cleaving of the RNA/DNA heteroduplexes which led some of the guanine-rich sequences escape from the nanochannels and thus reduced the formation of the G-quadruplex/hemin complex. Therefore, the quantity of methylene blue fluxed through the nanochannels changed because of the variation of the steric hindrance. A optimized carbon nanofibers modified electrode was applied to monitor the quantity difference of methylene blue. In this way, the biosensing platform realized the label-free electrochemical detection of MiR-21 with a ultralow detection limit of 0.5 aM. Meanwhile, this biosensing platform was assessed for MiR-21 detection in serum samples. The biosensing platform can be readily extended to the assay of other scarcetumor-related genes.