Development of a new biosensor based on functionalized SBA-15 modified screen-printed graphite electrode as a nano-reactor for Gquadruplex recognition

Gquadruplex is an active target for therapeutic purposes because of the evidence which suggest that G-rich region of the human genome may form Gquadruplex structure. The electrochemical biosensor was prepared by modifying screen-printed graphite electrode (SPE) with synthesized SBA-N-propylpipyrazine-N-(2-mercaptopropane-1-one) (SBA@NPPNSH) mesoporous structure to investigate the Gquadruplex DNA structure (G(4)DNA). Ascorbic acid (AA) is known as an antioxidant agent that induces reductive properties. It is also important for some therapeutic purposes. In this study, AA was used as the model ligand and its ability to interact with Gquadruplex structure was examined. The pore of SBA@NPPNSH structure can act as a nano-reactor and the interaction of G(4)DNA/AA is accomplished inside these channels. The structure of SBA@NPPNSH was characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA) methods and atomic force microscopy (AFM). The interaction of AA with G(4)DNA was studied in Tris-HCl buffer and also in the presence of [Fe(CN)(6)](3-) as a redox label using the CV method. CV current decreases with the increasing concentrations of AA due to the interaction of G(4)DNA/AA. Circular dichroism (CD) spectroscopy was used to examine the ability of AA to form Gquadruplexes from short and long complementary G(4)DNA strands. Studying the selectivity using different dsDNA sequences revealed that AA could stabilize G(4)DNA. Thus, the proposed biosensor can distinguish G(4)DNA structure from other dsDNA structures. (C) 2013 Elsevier B.V. All rights reserved.