Array-Based Electrical Detection of DNA with Nanoparticle Probes So-Jung Park, T. Andrew Taton, and Chad A. Mirkin

Supplementary Material

Supplemental Figure 1. An FE-SEM image of the edge of a DNA spot after the nanoparticle assembly and silver deposition process. The substrate has been treated with a higher concentration of nanoparticles (10 nM), which induces nonspecific binding of nanoparticles on the area where there is no capture DNA strands (below arrow). Note that there is no significant silver deposition below the arrow, even though there is a fair amount of nonspecifically bound nanoparticles. This further demonstrates that the silver reduction catalyzed by deposited silver is responsible for the closing of the gap rather than uniform enlarging of the particles.

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Supplemental Figure 2. Resistance of the electrode gaps as a function of enhancing time under thermal stringency. The array was washed with 0.3 M PBS at 50 °C prior to silver enhancing.

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Supplemental Figure 3. UV-vis spectrum of nanoparticle-functionalized glass cuvettes for (A) the perfectly complementary oligonucleotide (X = A) and (B) the strand with a wobble mismatch (X = G) after washing them with buffer solutions with different NaCl concentrations (black: 0.3 M PBS, red: 0.01 M PBS, blue: water).

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