The luminescent Nb₂C MXene nanosheet-based whispering gallery mode-enhanced ECL strategy for miRNA-214 detection

MiRNA-214 can regulate the expression of their downstream target genes after post-transcriptional and are involved in the biological processes of triple negative breast cancer (TNBC). In this work, the small-sized luminescent Nb₂C nanosheet-based whispering gallery mode-enhanced electrochemiluminescence (ECL) strategy was successfully constructed to detect miRNA-214 in TNBC. Firstly, we have synthesized small-sized luminescent Nb₂C nanosheets from Nb₂AlC MXene. The Nb₂C nanosheets not only exhibited more stable chemical properties and reduced the defects of the large sheet structures, but also possessed the quantum confinement effect with the discrete energy level. As a result, the prepared small-sized Nb₂C nanosheets had unique luminescent and electrochemical properties. Furthermore, in order to improve the ECL performance of Nb₂C nanosheets, SiO₂ microspheres were self-assembled on the electrode surface by gas-liquid interface method to form whispering gallery mode structure. Because the light was continuously reflected at the interface of the microcavity in the whispering gallery mode, the ECL signal of Nb₂C luminescent nanosheets was amplified largely. Finally, the whispering gallery mode-based ECL sensing platform was established. The results showed that the biosensor had a good linear correlation between the ECL intensity and the logarithm of concentration of miRNA-214 in the range of 10 fM to 100 nM with a limit of detection of 2.5 fM. The actual detection of miRNA-214 content in clinical TNBC tissue samples was realized successfully.