Magnetically trigged direct electrochemical detection of DNA hybridization using Au quantum dot as electrical tracer

A novel gold nanoparticle-based protocol for detection of DNA hybridization based on a magnetically trigged direct electrochemical detection of gold quantum dot tracers is described. It relies on binding target DNA (here called DNA1) with Au quantum dot in a ratio 1:1, followed by a genomagnetic hybridization assay between Au-DNA1 and complementary probe DNA (here called DNA2) marked paramagnetic beads. Differential pulse voltammetry is used for a direct voltammetric detection of resulting Au quantum dot-DNA1/DNA2-paramagnetic bead conjugate on magnetic graphite-epoxy composite electrode. The characterization, optimization, and advantages of the direct electrochemical detection assay for target DNA are demonstrated. The two main highlights of presented assay are (1) the direct voltammetric detection of metal quantum dots obviates their chemical dissolution and (2) the Au quantum dot-DNA1/DNA2-paramagnetic bead conjugate does not create the interconnected three-dimensional network of Au-DNA duplex-paramagnetic beads as previously developed nanoparticle DNA assays, pushing down the achievable detection limits. © 2005 American Chemical Society.