DNA Analysis Based On The Electrocatalytic Amplification Of Gold Nanoparticles

The detection of deoxyribonucleic acid (DNA) has a very important significance in life sciences. Combining with electrochemistry and life science, this paper provides a new and effective electrochemical detection method of low concentrations DNA.First, the paper demonstrates the electrocatalytic activity of DNA-modified Au NPs and its enhancement. The Au NPs of collosol were synthesized. Hydrazine oxidation on DNA-modified Au NP and the influence of electrocatalytic activity of Au NP via NaBH4treatment were detected by cycle voltammetry (CV). The results showed that the Au NP of3-4nm diameters had large specific surface area and less prone to agglomeration with good electrocatalytic activity. Au NP could enhance hydrazine electrooxidation current. However the binding capping agent DNA layer on Au NP observably decreased the electron transfer kinetics for hydrazine electrooxidation. With it the electrocatalytic activity of Au NP labels was decreased. But NaBH4chemical treatment could substantially provide high currents for hydrazine electrooxidation at low applied potentials and increase the electrocatalytic activity of Au NP.Second, the paper observes single Au NP collision events as signal label to amplify electrocatalytic activity for hydrazine electrooxidation in an electrochemical DNA biosensor. DNA bioelectrode was assembled by sandwich-type, and made sure the best NaBH4treatment time. After this the electrocatalytic activity of Au NP in DNA detection and the influence of electrocatalytic activity via NaBH4treatment were discussed by CV, linear sweep voltammetry (LSV), and chronoamperometry (CA). Finally the detection limit of target DNA had been achieved. The results showed that15minute NaBH4treatment could obtain maximum electrocatalytic activity and was employed for the detection of target DNA. CV displayed that the peak shift increased with an increase of target DNA concentration, moreover it increased1.103×10-8-1.889×10-8A (in all cases, ultramicroelectrode radius is5μm) after NaBH4treatment. NaBH4treatment significantly enhanced the electrocatalytic activity of the Au NP, and fast electron-transfer kinetics was obtained. The fast kinetics substantially reduces the overpotential, thus the high sensibility of DNA sensor is achieved. LSV displayed when the target DNA concentration was1pM, the current was3.254×10-11A, which was clearly higher than the current of target DNA absence (1.113×10-11A). Target DNA could be detected ranging from1pM to100nM. CA displayed an approximate consideration of the current staircase response was observed when the concentrations of target DNA as low as1pM. When the Au NP was in contact with the Pt UME surface, a transient stepwise current could be obtained. While it leaved, the current ceased. The detection limit of target DNA was1pM. Test of mismatch discrimination of different target DNA indicated that the biosensor had good selectivity.