Size-Dependent Interactions
between Au Nanoparticles
and DNA in Electrochemical Oxidation by Metal Complexes
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Abstract
Single-stranded oligonucleotides (ssDNA) containing guanine
bases
in their sequences were adsorbed onto gold nanoparticles (AuNPs) by
electrostatic interaction. Cyclic voltammetry of Ru(bpy)<sub>3</sub><sup>2+</sup> in the presence of the ssDNA-AuNP complex resulted
in an enhanced anodic current due to the oxidation of the guanine
bases of DNA. The current obtained with ssDNA-AuNP appeared much smaller
than the corresponding ssDNA alone. This current reduction was due
to the decrease in solvent accessibility of the guanines in ssDNA
immobilized to AuNPs. A progressive decrease in the current was observed
in the titration of AuNPs to ssDNA, and a minimum current was eventually
obtained, indicating complete binding of ssDNA. The size dependences
of AuNPs on the interaction between ssDNA and AuNP were also studied,
and the ssDNA adsorbed to 5 nm AuNPs was more solvent-accessible for
the Ru mediator than 13 and 30 nm AuNPs