A DNA array detection method is reported in which the binding of oligonucieotides functionalized with gold nanoparticies leads to conductivity changes associated with target-probe binding events. The binding events localize gold nanoparticies in an electrode gap; silver deposition facilitated by these nanoparticles bridges the gap and leads to readily measurable conductivity changes. An unusual salt concentration-dependent hybridization behavior associated with these nanoparticie probes was exploited to achieve selectivity without a thermal-stringency wash. Using this method, we have detected target DNA at concentrations as low as 500 femtomolar with a point mutation selectivity factor of ∼ 100,000:1.
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