Detection of interaction between metal complex indicator and DNA by using electrochemical biosensor

There has been extensive research on binding of transition metal complexes to DNA via electrostatic and hydrophobic interactions. Most indicator based electrochemical DNA biosensors have used cationic metal complexes that int eract in a different way with single-stranded DNA (ssDNA) and double-strand ed DNA (dsDNA). Described here are the electrochemical parameters for a mix ed-ligand complex, [Co(phen)(3)(3+)] (phen: 1,10-phenanthroline), on bindin g to DNA. The milimolar quantities of [Co(phen)(3)(3+)], which associates r eversibly with immobilized calf thymus DNA was detected by using dsDNA-modi fied carbon paste electrode (dsDNA-modified CPE), ssDNA-modified carbon pas te electrode (ssDNA-modified CPE) and bare carbon paste electrode (bare CPE ), voltammetrically and the decreased peak currents were observed, respecti vely. The extend of hybridization between the complementary sequences is de termined by the enhancement of the voltammetric peak of the [Co(phen)(3)(3)] indicator. Numerous factors affecting the DNA irmnobilization and indica tor were investigated. Experiments were also performed at various salt conc entrations and the optimum salt concentration was determined. The differenc e between the peak currents of denaturated calf thymus DNA (ssDNA)-modified CPE and dsDNA-modified CPE was also observed. These results demonstrated t he use of the electroactive hybridization indicator, [Co(phen)(3)(3+)] for DNA biosensers.