Potential-resolved Faraday cage-type electrochemiluminescence biosensor for simultaneous determination of miRNAs using functionalized g-C3N4 and metal organic framework nanosheets.

Here, a novel Faraday cage-type electrochemiluminescence (ECL) biosensor was presented for simultaneous determination of miRNA-141 and miRNA-21 based on the potential-resolved strategy. In this work, capture units were prepared by immobilizing hairpin DNA1 (HP1) and hairpin DNA2 (HP2) on Fe3O4 @Au nanocomposites, while g-C3N4 @AuNPs nanocomposites labelled by signal DNA1 (sDNA1) and ruthenium-based metal organic framework (Ru-MOF) nanosheets labelled by signal DNA2 (sDNA2) were used as signal units. In this proposed biosensor, signal units g-C3N4 @AuNPs-sDNA1 and Ru-MOF-sDNA2 could exhibit two strong and stable ECL emissions at - 1.4 V and + 1.5 V respectively, which could be used as effective potential-resolved signal tags. Moreover, taking advantage of the proposed Faraday cage-type model, all electrochemiluminophores in the signal units could take part in electrode reactions, the signal units became part of the electrode surface and extended the outer Helmholtz plane (OHP) of the proposed electrode, and then the detection sensitivity was improved greatly. Accordingly, dual targets miRNA-141 and miRNA-21 could be detected within the linear range of 1 fM to 10 pM, with the detection limit of 0.3 fM. Meanwhile, the proposed miRNA assay exhibited high selectivity and sensitivity, even for practical analysis in human serum. So, this potential-resolved ECL biosensor is proved to be a feasible tool for dual targets detection of miRNAs in clinical diagnosis.