Electrochemical microRNA detection based on catalytic deposition of G-quadruplex DNAzyme in nanochannels

Abnormal expression and functioning of microRNAs in the immune system are frequently linked to various cancers. Our previous work demonstrated a universal, label-free, and reliable microRNA detection platform based on the nanochannels-based recognition interface and electrode-based sensing interface. Herein, the strategy of G-quadruplex DNAzyme-catalyzed deposition was introduced into the nanochannels to improve the detection sensitivity of the platform. G-quadruplex DNAzyme could catalyze the oxidation of 4-chloro-1-naphthol to produce insoluble precipitates into the nanochannels which amplified the effect of the hybridization reaction between the capture probe and the target to the mass transport of the redox probe through the recognition interface. Then, a porous carbon nanofibers-modified electrode was applied to further amplify the monitoring sensitivity of the sensing interface to the concentration change of the redox probe methylene blue. Thereby, sensitive electrochemical detection of microRNA-21 was acquired. The biosensing platform exhibited a broad linear range of 100 aM to 1 nM for microRNA-21, with a low detection limit of 40 aM. What is more, the selective and reproducible platform provided an alternative technique for the PCR-free determination of microRNA in serum and tumor cells. Graphical abstract