Double-site DNA walker based ternary electrochemiluminescent biosensor.

A novel biosensor was developed on the basis of Ru(dcbpy)(bpy)22+/tripropylamine (TPrA)/TiO2 nanocrystallines (TiO2 NCs) as efficient electrochemiluminescence (ECL) ternary system and enzyme-driven double-site DNA walker as signal amplification strategy for the sensitive detection of carcinoembryonic antigen (CEA). Specifically, coreaction accelerator anatase TiO2 NCs with catalytic activity could accelerate the oxidization of TPrA for prominently stimulating the ECL performance of Ru(dcbpy)(bpy)22+/TPrA system to achieve the "signal on" state. Subsequently, numerous double-site walker DNA, converted from the target (CEA)-induced protein-aptamer cycle amplification, would trigger the detachment of Ru(dcbpy)(bpy)22+ to reach the state of "signal-off". Benefiting from the above advantages, the developed ECL biosensor achieved outstanding sensitivity with a linear range from 500 pg/mL to 50 fg/mL and a detection limit down to 10.5 fg/mL. More importantly, the proposed strategy opens a new path for employing the ECL ternary system for sensitive detection of biomolecules and disease diagnosis.