A three-dimensional DNA nanomachine with target recycling amplification technology and multiple electrochemiluminescence resonance energy transfer for sensitive microRNA-141 detection.

An electrochemiluminescence (ECL) three-dimensional (3D) DNA nanomachine is developed for microRNA-141 (miRNA-141) detection by coupling Pb2+ dependent DNAzyme assisted target recycling amplification technology with multiple ECL resonance energy transfer (ECL-RET) system. Firstly, Pb2+ dependent DNAzyme is formed by three single strand DNA (ssDNA): A1, A2 and the target miRNA-141. In the presence of Pb2+, the specific recognition site of the DNAzyme is cleaved and a large number of secondary targets (A3) are released. Secondly, the 3D DNA nanomachine consists of four ssDNA: H1, H2, H3 and the probe (two ends are labeled with alexa fluor (AF) and a nanocomposite (PtNCs@Ru(dcbpy)32+) which is prepared by polyethyleneimine platinum nanoclusters and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) dichloride). Then, the 3D DNA nanomachine is assembled on the gold nanoparticles modified glassy carbon electrode. Afterwards, A3 is employed to hybridize with the probe, triggering the movement of the nanomachine and forming the multiple ECL-RET system. In this system, AF, serves as an effective energy transfer donor, which can transfer energy to PtNCs and Ru(dcbpy)32+directly. Meanwhile, PtNCs, both as the acceptor and donor, can accept energy from AF and transfer it to Ru(dcbpy)32+. As a result, The biosensor achieves enhanced ECL efficiency, which is 1.78 times that of the classic tris(2,2'-bipyridyl)ruthenium(II) dichloride (Ru(bpy)32+) and exhibits good responses to miRNA-141 in the linear range from 10 aM to 100 nM with a detection limit of 3.3 aM. Also, the obtained biosensor can be employed to detect miRNA-141 in human serum samples, which will be of great significance in bioanalysis.