Electrochemical DNA Biosensors Based On Nano-interface Control

The electrochemical DNA biosensor is a special kind of biosensors. Because electrochemical detectors are inexpensive, portable and power-saving, electrochemical DNA biosensors have been widely recognized to be a highly promising approach to detect clinically, environmentally and security relevant nucleic acids, especially when time, money or resources are limited. However, the development of a high sensitive electrochemical DNA sensor will still face many challenges. DNA recognition and hybridization was limited by the accessibility of target DNA to probes on the heterogeneous electrode surface due to the reduced mass transport and the surface crowding effects. The nanotechnology provides solution to the problems occurred in electrochemical DNA sensors. We can endow nanosensing interface excellent water-soluble, chemically stable and biocompatible. We developed multivariate, collaborative nanosensing interfaces by using gold nanotip electrode and DNA tetrahedron nanostructure, and regulated nanosensing interfaces to achieve the the high specificity of capture beteween the probe and the target. The main results were described as following:1. The nanotip electrodes were fabricated by electrochemical etching of gold wires, which were then insulated with the electrophoretic paint. Then thiolated DNA capture probe was immobilized on a gold nanotip electrode to form a self-assembled monolayer via the strong Au–S interaction. We also interrogated the effect of DNA surface density on efficiencies of hybridization-relevant electrocatalytic reactions, by using the Ru(NH3)63+/Fe(CN)63- system. Curved surfaces of the nanotip favor efficient hybridization due to the reduced steric interactions between immobilized strands. In addition, electrocatalytic efficiency is highly dependent on density of DNA monolayers, as a result, DNA and miRNA-141 hybridization can turn on electrocatalysis by increasing the DNA surface density.2. We have developed a high sensitive telomerase sensor based on a spired DNA tetrahedron TS primer. Usually, the telomerase extension reaction in the liquid phase is apt to happen, and the reaction on the solid liquid interface is relatively difficult. We found that the electrode surface decorated with spire DNA tetrahedron primers greatly facilitates the extension of telomerase. This novel design leads to a sensitive telomerase sensor with a remarkably low detection limit of 10 HeLa cells.3. We utilized the DNA tetrahedron probes to establish a sandwich-type electrochemical DNA biosensor for electrochemical analysis of a 250 bp unpurified PCR amplicons of uidA gene of E.coli genome. The three-dimensional(3D) DNA tetrahedral nanostructure can improve the ability for biomolecular sensing, through the improved accessibility of the probes and the better density control of the DNA probes on the surface. In addition, The DNA tetrahedron greatly restrained the unspecific adsorption, which can ensure a high selectivity in complex actual sample.