[[Ru[(bpy).sub.2]dppz].sup.2+] electrochemiluminescence switch and its applications for DNA interaction study and label-free ATP aptasensor

[[Ru[(bpy).sub.2]dppz].sup.2+] electrochemiluminescence (ECL) was studied, and it was used to investigate DNA interaction and develop a label-free ATP aptasensor for the first time. ECL of [[Ru[(bpy).sub.2]dppz].sup.2+] is negligible in aqueous solution, and increases ~1000 times when [[Ru[(bpy).sub.2]dppz].sup.2+] intercalates into the nucleic acid structure. The ECL switch behavior of [[Ru[(bpy).sub.2]dppz].sup.2+] is ascribed to the intercalation that shields the phenazine nitrogens from the solvent and results in a luminescent excited state. The ECL switch by DNA was applied to investigate the interaction of [[Ru[(bpy).sub.2]dppz].sup.2+] with herring sperm DNA. The calculated equilibrium constant (K) is 1.35 x [10.sup.6] [M.sup-1], and the calculated binding-site size (s) is 0.88 base pair, which is consistent with the reported values. Moreover, ATP can dramatically affect ECL of the [[Ru[(bpy).sub.2]dppz].sup.2+]/ATP aptamer complex. As a result, a label-free, sensitive, and selective [[Ru[(bpy).sub.2]dppz].sup.2+] ECL method for ATP detection was developed. The detection limit is 100 nM for ATP (with a signal-to-noise ratio, S/N, of 3) with a linear range of 0-1 [micro]M. The result demonstrates that [[Ru[(bpy).sub.2]dppz].sup.2+] ECL holds great promise in aptasensors. 10.1021/ac901925x