Poly(indole-5-carboxylic acid)-functionalized ZnO nanocomposite for electrochemical DNA hybridization detection

In this paper, a novel direct DNA electrochemical biosensor was developed for detection of breakpoint cluster region gene and the cellular abl (BCR/ABL) fusion gene from chronic myelogenous leukemia. Nanosized ZnO was first immobilized on the surface of a carbon paste electrode, and then poly(indole-5-carboxylic acid) (PICA), a new electroactive material, was electropolymerized on the ZnO substrate by using the potentiostatic method to form a unique nanocomposite structure. The obtained PICA/ZnO nanocomposite not only served as a substrate for DNA immobilization but also reflected the electrochemical transduction originating from DNA immobilization and hybridization without any outer indicators or complicated labeling. The immobilization of probe DNAwas successfully conducted via covalent bonding between the abundant carboxyl groups of PICA/ZnO nanocomposite film and amino groups at the 5'-end of probe DNA. After the hybridization of probe DNA with target DNA, the formation of double-helix structure induced the signal-on of the nanocomposite. The dynamic range of this DNA biosensor for detecting the complementary target sequence of BCR/ABL fusion gene was from 1.0x10(-15) to 1.0x10(-9) mol/L using electrochemical impedance spectroscopy, and the detection limit was estimated to be 2.2x10(-16) mol/L.