A new methodology for electrostatic immobilization of a non-labeled single strand DNA onto a self-assembled diazonium modified gold electrode and detection of its hybridization by differential pulse voltammetry

In this work, a self-assembled diazonium modified gold electrode (D-MGE) was used for the fabrication of an electrochemical DNA biosensor. For preparation of D-MGE, initially 2-amino-5-mercapto-1, 3, 4-thiadiazole (AMT) self-assembled on gold electrode and a simple diazonation reaction was used to prepare D-MGE. Then, non-labeled single strand DNA (NL-ssDNA) directly was immobilized on D-MGE through electrostatic interaction. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) characterized the DNA biosensor fabrication process with the use of ferro-ferric cyanide as an electrochemical redox indicator. The hybridization capacity of the developed biosensor was monitored with differential pulse voltammetry using [Fe (CN)6]4− as an indicating probe. A wide dynamic detection range (7.9×10−11–1.2×10−7 mol L−1) and a low detection limit (1.4×10−11 mol L−1) were achieved for the complementary sequence. In addition, the hybridization specificity experiments showed that the sensing system could accurately discriminate complementary sequence from non-complementary sequences.