An Enzyme-Free Electrochemical DNA Biosensor Based on Multimeric Tetrahedral DNA for Rapid Detection of Trance Heavy Metal Ions

Abstract

Electrochemical DNA biosensors are usually used to detection targets by converting hybridization events between the specific nucleic acids and the modified transducers into measurable electrical signals. However, their electrode modification needs multiple assembly steps, which results in low controllability of assembly at the DNA-electrode interface. In addition, the traditional electrochemical DNA biosensors cannot meet the requirements of the trace analyte due to the insufficient sensitivity. Herein, a novel electrochemical DNA biosensor utilizing one-step electrode modification (only the immobilized H1 probe needed) was fabricated for rapid enzyme-free analysis of the heavy metal ions (Pb2+ used as a model target). At the detection system, single strands DNA (ssDNA) will be generated through Pb2+-dependent DNAzyme and captured by the H1 probe on the electrode surface. Furthermore, the multiple DNA tetrahedral nanostructures (M-TDNs) carriers modified by methylene blue as the signal tag were bound with H1, which displaced ssDNA for catalytic hairpin assembly (CHA) to amplify signal. Under the optimized conditions, the constructed biosensor exhibits a low detection limit of 0.033 pM for Pb2+, ascribed to the abundant MB binding domains of M-TDNs and signal amplification by CHA. Our approach provides some novel insights on electrochemical DNA biosensors establishment.

Keywords: Signal amplification, electrochemical sensor, rapid detection, Simple electrode modification, Biosensor