Electrochemical DNA biosensor based on nanoporous gold electrode and multifunctional encoded DNA-Au bio bar codes

A sensitive electrochemical DNA sensor based on nanoporous gold (NPG) electrode and multifunctional encoded Au nanoparticle (AuNP) was developed. The NPG electrode was prepared with a simple dealloying strategy, by which silver was dissoluted from silver/gold alloys in nitric acid, making the active surface area of NPG electrode 9.2 times higher than that of a bare flat one characterized by cyclic voltammetry. A DNA biosensor was fabricated by immobilizing capture probe DNA on the NPG electrode and hybridization with target DNA, which further hybridized with the reporter DNA loaded on the AuNPs. The AuNP contained two kinds of bio bar code DNA, one was complementary to the target DNA, while the other was not, reducing the cross reaction between the targets and reporter DNA on the same AuNP. Electrochemical signals of [Ru(NH3)6]3+ bound to the reporter DNA via electrostatic interactions were measured by chronocoulometry. Taking advantage of dual-amplification effects of the NPG electrode and multifunctional encoded AuNP, this DNA biosensor could detect the DNA target quantitatively, in the range of 8.0 x 10(-17)-1.6 x 10(-12) M, with a limit of detection as low as 28 aM, and exhibited excellent selectivity even for single-mismatched DNA detection.