Ultrasensitive electrochemiluminescence biosensor based on dual quenching effects of silver nanoclusters and multiple cycling amplification for detection of ATP.

In this work, an electrochemiluminescence (ECL) biosensor based on dual ECL quenching effects of silver nanoclusters (Ag NCs) and multiple cycling amplification was designed to achieve ultrasensitive detection of ATP. The specific recognition of target ATP to aptamer initiated multiple cycling amplification, and a small amount of target was converted into a large number of DNA product chains (S1) by amplification. After S1 opened hairpin DNA 2 (HP2), Ag NCs approached the surface of CdS quantum dots (QDs) modified-electrode by complementary DNA, resulting in a significant decrease of ECL intensity from CdS QDs. The quenching principle is as follows. Firstly, the absorption spectrum of Ag NCs overlaps well with the ECL emission spectrum of CdS QDs, leading to effective ECL resonance energy transfer (ECL-RET); Secondly, Ag NCs could catalyze electrochemical reduction of K2S2O8, leading to consumption of ECL co-reactant and reducing ECL of QDs. The double-ECL quenching achieved ultrasensitive biosensing detection of ATP with a wide range from 1 aM to 1 pM. This present work reported new principle of double-quenching QDs ECL by Ag NCs, and developed a novel ECL biosensor by combining with multiple cycle amplification technique, which has great contribution to the development of QDs ECL and biosensing applications.

Studies on the interaction mechanism between hexakis(imidazole) manganese(II) terephthalate and DNA and preparation of DNA electrochemical sensor.

The interaction between hexakis(imidazole) manganese(II) terephthalate ([Mn(Im)(6)](teph).4H(2)O) and salmon sperm DNA in 0.2M pH 2.30 Britton-Robinson buffer solution was studied by fluorescence spectroscopy and cyclic voltammetry. Increasing fluorescence was observed for [Mn(Im)(6)](2+) with DNA addition, while quenching fluorescence phenomenon appeared for EB-DNA system when [Mn(Im)(6)](2+) was added. There were a couple quasi-reversible redox peaks of [Mn(Im)(6)](2+) from the cyclic voltammogram on the glassy carbon electrode. The peak current of [Mn(Im)(6)](2+) decreased with positive shift of the formal potential in the presence of DNA compared with that in the absence of DNA. All the experimental results indicate that [Mn(Im)(6)](2+) can bind to DNA mainly by intercalative binding mode. The binding ratio of the DNA-[Mn(Im)(6)](2+) association complex is calculated to be 1:1 and the binding constant is 4.44x10(3) M(-1). By using [Mn(Im)(6)](teph).4H(2)O as the electrochemical hybridization indicator, the DNA electrochemical sensor was prepared by covalent interaction and the selectivity of ssDNA modified electrode were described. The results demonstrate the use of electrochemical DNA biosensor in the determination of complementary ssDNA.