Ultra-sensitive electrochemiluminescence monitoring of microRNA via Triton X-100 functionalized carbon dots-based nanocomposites

Carbon dots (CDs) with excellent optical performance have attracted tremendous interest for the construction of electrochemiluminescence (ECL) biosensors. However, the intrinsic self-aggregation behavior of CDs brings a serious issue of aggregation-caused quenching (ACQ), which can quench the ECL emission. In this work, different surfactants (non-ionic, anionic and cationic) were used to modulate the preparation of functionalized CDs (CDs-based nanocomposites). Their ECL performances were significantly enhanced in potassium persulfate solution. In particular, the highest ECL intensity obtained from the Triton X-100 functionalized CDs (T-CDs) was 16.8-fold than that of CDs as ACQ was suppressed effectively. Therefore, utilizing T-CDs as an ECL luminophore, integrating with the catalytic hairpin assembly and strand displacement reaction signal amplification strategies, a "Signal on" ECL biosensor was constructed for microRNA-21 (miRNA-21) monitoring. The proposed biosensor shows a dynamic range from10 fmol·L −1 to 10 nmol·L −1 at a low detection limit of 2.9 fmol·L −1 (S/N = 3). Meanwhile, it exhibits good results for analyzing miRNA-21 in healthy human samples and the expression in MCF-7 and HeLa cells. This work not only expands the method for suppressing ACQ of CDs, but also shows great potential for the analysis of other biomarkers by replacing the corresponding DNA sequences , so as to realize the early diagnosis.