"Off-On"switching electrochemiluminescence biosensor for mercury(II) detection based on molecular recognition technology.

A novel "off-On" electrogenerated chemiluminescence (ECL) biosensor has been developed for the detection of mercury(II) based on molecular recognition technology. The ECL mercury(II) biosensor comprises two main parts: an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Ruthenium(II) tris-(bipyridine)(Ru(bpy)32+)/Cyclodextrins-Au nanoparticles(CD-AuNps)/Nafion on the surface of glass carbon electrode (GCE), and the ECL intensity switch is the single hairpin DNA probe designed according to the "molecular recognition" strategy which was functionalized with ferrocene tag at one end and attached to Cyclodextrins (CD) on modified GCE through supramolecular noncovalent interaction. We demonstrated that, in the absence of Hg(II) ion, the probe keeps single hairpin structure and resulted in a quenching of ECL of Ru(bpy)32+. Whereas, in the presence of Hg(II) ion, the probe prefers to form the T-Hg(II)-T complex and lead to an obvious recovery of ECL of Ru(bpy)32+, which provided a sensing platform for the detection of Hg(II) ion. Using this sensing platform, a simple, rapid and selective "off-On" ECL biosensor for the detection of mercury(II) with a detection limit of 0.1 nM has been developed.

An electrochemical DNA sensor without electrode pre-modification.

We present a non-modification electrochemical DNA sensing strategy, which used Potential-Assisted Au-S Deposition and a clamp-like DNA probe. The dual-hairpin probe DNA was tagged with a methylene blue (MB) at the 3' terminal and a thiol at the 5' terminal., Without being hybridized with target DNA, the loop of probe prevented the thiol from reaching the bare gold electrode surface with an applied potential., After hybridization with the target DNA, the probe' s loop-stem structure opened through two distinct and sequential events, which led to the formation of a triplex DNA structure. Then the thiol easily contacted with electrode and resulted in potential-assisted Au-S self-assembly. Electrochemical signals of MB were measured by differential pulse voltammetry (DPV) and used for target quantitative detection. This strategy offered a detection limit down to 2.3pM. and an inherently high specificity for detecting even single mismatch.