Highly Efficient Electrochemiluminescence Resonance Energy Transfer System in One Nanostructure: Its Application for Ultrasensitive Detection of MicroRNA in Cancer Cells

The electrochemiluminesce (ECL) efficiency of luminous emitter can be enhanced by the means of electrochemiluminesce resonance energy transfer (ECL-RET) with a matched donor. However, generally, the donor and acceptor pairs were separated in different independent nanostructures, experiencing the challenging issues of limited energy transfer efficiency and luminous stability. Herein, we designed novel ECL-RET model within one nanostructure containing the donor of tris(4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)₃²⁺) and the acceptor of CdSe@ZnS quantum dots (QDs) for acting as the ECL emitter (QDs-Ru(dcbpy)₃²⁺), which significantly reduced the energy loss and improved the ECL efficiency of QDs because of the short path of energy transmission. To demonstrate the proof-of-concept, the proposed QDs-Ru(dcbpy)₃²⁺ was employed to construct a new kind of ECL biosensor that could achieve the ultrasensitive detection of microRNA-141 (miRNA-141) combining target recycling amplification and the double-output conversion strategies. Notably, the proposed double-output conversion strategy enabled a small number of miRNA to be successfully transferred into a large number of reporter DNA which could capture numerous QDs-Ru(dcbpy)₃²⁺-labeled signal probes on the sensing surface to realize the ECL response to the logarithm of the concentration of miRNA-141. With the ultrahigh-efficient ECL-RET in one nanostructure and the dual amplification including target recycling as well as double-output conversion strategies, the proposed biosensor realized ultrasensitive detection of miRNA-141 and performed the concentration range from 100 aM to 10 pM and the estimated detection limit was 33 aM (S/N = 3). Impressively, this method can sensitively detect the miRNA-141 of human prostate cancer cells and provide a significant boost for the detection of other biomarkers in early cancer diagnosis and therapeutic monitoring.