Fabrication Of Nano-modified Electrode And Its Appilication In DNA Biosensor

In this article, three simple and robust strategies for DNA immobilization on gold electrode surface were developed via the fine-tune study of the electrode surface.In chapter two, a simple strategy of electroless deposition of gold nanoparticles (Au NPs) on the conductive substrate was developed. The morphology of Au NPs modified electrode could be controlled to some extent by choosing different solution concentration, deposition time, etc. The Au NPs modification increased the surface area largely and the surface area for Au NPs modified on the polyelectrolyte multilayer (PEM) assembled electrode was about 3.3 times of that of planar gold electrode.In chapter three, a robust strategy for DNA immobilization on gold electrode surface via in situ generation of dithiocarbamate (DTC) ligands was developed. Compared with conventional HS-DNA immobilization method, the immobilized DTC-DNA could offer more strong adhesion ability on gold surface. The ac impedance experiments showed that the density of probe DTC-DNA could be more effectively adjusted for higher hybridization efficiency due to its bidentate anchoring points on gold surface.In chapter four, hollow gold nanospheres (HGN) were prepared by using Co nanoparticles as sacrificial templates and varying the stoichiometric ratio of HAuCl4 over the reductants. The HGN was then modified on the electrode surface via a 1,6-hexanedithiol linking agent to fabricate a novel electrochemical DNA biosensor.The whole DNA biosensor fabrication process was characterized by cyclic voltammetry (CV) or electrochemical impedance spectra (EIS) with the use of ferricyanide as the electrochemical redox indicator. The DNA immobilization and hybridization on the modified electrode was further studied with CV and differential pulse voltammetry (DPV) methods by using Ru(NH3)63+ or Co(phen)33+ , respectively as an electrochemical hybridization indicator. Results revealed that the modified electrode could largely enhance the DNA hybridization ability. The fabricated DNA biosensor was proved to have a low detection limit (1×10-11M ,1×10-10 M or 1 pM, respectively) toward complementary target DNA and with a high stability and reusability.The current strategies were readily to perform with, less time consuming and less expensive compared with those commonly used strategies. The current fabricated DNA biosensor architecture should be also suitable for the detection of target DNA in real samples, for example clinical analytes. Moreover, these electrode modification strategies were expected for further extensive applications in protein, enzyme biosensors.