Heterogeneous electrochemiluminescence spectrometry of Ru(bpy)32+ for determination of trace DNA and its application in measurement of gene expression level

In this paper, we reported an ultrasensitive ECL spectrometry for determination of DNA using magnetic streptavidin-coated nanobeads MNBs (SA-MNBs) as the carrier of Ru(bpy)32+-NHS, where bpy = 2,2′-bipyridyl and NHS = N-hydroxysuccinimide ester, to amplify signal. The SA-MNBs were conjugated to the hybrids consisting of capture DNA, target DNA (t-DNA) and probe DNA immobilized on a substrate, followed by releasing the SA-MNBs and binding a huge number of Ru(bpy)32+-NHS to the SA-MNBs. The SA-MNBs with Ru(bpy)32+-NHS were immobilized on an Au film electrode by means of a magnet. In the presence of tri-n-propylamine, the ECL spectrum of the Ru(bpy)32+-NHS at 1.35 V was acquired by using an optical multi-channel analyzer. The maximum emission intensity on the ECL spectrum was used to quantify DNA. Using this method, not only the limit of detection for DNA determination was as low as 1.2 × 10−15 mol/L, but also the ECL spectrum of Ru(bpy)32+-NHS on the surface of the SA-MNBs was obtained. The ultrasensitive ECL spectrometry could be used to measure gene expression level in cells.