Linear sweep voltammetric studies on the interaction of brilliant cresyl blue with nucleic acids and its analytical application

In this paper, the interaction of brilliant cresyl blue (BCB) with nucleic acids was studied and further applied for the microdetermination of nucleic acids. In aqueous Britton-Robinson (B-R) buffer solution, BCB can be easily reduced on the hanging mercury drop electrode (HMDE) and had a sensitive voltammetric reduction peak at -0.09 V (vs. SCE). The reduction peak current of BCB could be greatly decreased by the addition of DNA. The results of voltammetric measurements had indicated that a binding reaction was occurred between BCB and DNA and a new supramolecular complex was formed, which resulted in the decrease of the diffusion coefficient of the reaction solution and the decrease of the reduction peak current correspondingly. The conditions of interaction and the electrochemical detection were carefully investigated. Under the selected conditions, the calibration curves for the detection of fish sperm (fs)DNA, calf thymus (ct)DNA and yeast (y)RNA were established. The linear range of this assay was 1.0-30.0 mu g/mL for fsDNA, 1.0-45.0 mu g/mL for ctDNA and 1.0-25.0 mu g/mL for yRNA, respectively. The detection limits were 0.38 mu g/mL fsDNA, 0.43 mu g/mL ctDNA, 0.64 mu g/mL yRNA. The interaction parameters such as the equilibrium constant and the binding number were calculated by electrochemical method. The results showed that the 2:3 type of complex was formed in the fsDNA-BCB complex with the binding constant as 2.51x10(7). The proposed method was further applied to the synthetic samples determination with satisfactory results.