Electrogenerated chemiluminescence energy transfer and its application in label-free sensing long DNA

An easily operated label-free DNA sensor for sensing long DNA molecule based on electrogenerated chemiluminescence (ECL) energy transfer from luminol to [Ru(bpy)3]2+ was proposed in this work. Excited luminol was used as energy donor and [Ru(bpy)3]2+ combined with DNA as energy acceptor. ECL reaction of luminol was triggered by step pulse signal and excited luminol molecules transferred their energy to [Ru(bpy)3]2+ molecules. Excited [Ru(bpy)3]2+ molecules released energy in photon form in the process of going back to the ground state. Compared with single-stranded DNA (ssDNA), double-stranded DNA (dsDNA) binds more [Ru(bpy)3]2+ molecules mainly be electrostatic attraction, which results in stronger ECL intensity from [Ru(bpy)3]2+-dsDNA. Most important, the proposed method can detect DNA with length as long as the thickness of diffusion layer theoretically. In this work, 15 bps DNA was used as a model to investigate the ECL energy transfer behaviors and the analytical performance of DNA detection. Under optimal conditions, the label-free DNA ECL biosensor showed a good linear range over 1.0 × 10−14 mol/L to 1.0 × 10−10 mol/L with detection limit of 2.0 × 10−15 mol/L for 15 bps DNA. What is more, this proposed method could distinguish ssDNA and dsDNA with 35 bps and 100 bps, which exceeded the upper limit in fluorescence resonance energy transfer and electrochemical methods.