Comparative Study of Redox Targeting of DNA Anchored to MWCNTs and TiO2 Nanoparticles Dispersed In Poly Dialyldimethylammonium Chloride And Chitosan, Colloids Surface B, 2014, 121, 99–105., A.A. Ensafi, P.Nasr-Esfahani, E. Heydari-Bafrooei, B. Rezaei

tA key issue associated with electrochemical DNA-based biosensors is how to enhance DNA immobiliza-tion on the substrates. In order to improve the immobilization of DNA and to optimize DNA interactionefficiency, different kinds of strategies have been developed. In this regard, nanomaterials have attracteda great deal of attention in electrode surface modification for DNA biosensor fabrication. In this study,nanostructured films were deposited at the surface of a pencil graphite electrode (PGE) as a workingelectrode. For the present purpose, common polyelectrolytes are used for surface modification withdouble-stranded DNA. Two positively charged polyelectrolyte, namely poly dialyldimethylammoniumchloride (PDDA) and chitosan, are initially compared for DNA immobilization at the surface of MWCNTsand TiO2nanoparticles (TiO2NPs). In a second step, the basic electrochemical properties of the sensorsare investigated using voltammetric methods. The modified electrodes are also characterized by scan-ning electron microscopy and electrochemical impedance measurements. It will be shown that electrodemodification with DNA and the nanostructure that disperses in PDDA leads to an enhanced sensitivityof the DNA voltammetric detection mechanism. In a previous study, a comparison was done betweenMWCNTs and TiO2NPs for determining the effect of nanoparticle effect on DNA immobilization on theelectrode surface. In order to compare the efficiency of the prepared DNA-based biosensors, methyleneblue is chosen as an electroactive probe. It will be shown that the stability of the immobilized DNA withinseveral days will be much higher when MWCNTs rather than TiO2NPs are used.