Gold nanoparticles exhibit unique colorimetric properties due to plasmonic coupling that make them an ideal material for sensitive colorimetric sensors. DNA reaction networks have been incorporated with gold nanoparticles to produce an aggregation based detection mechanism for DNA. Aggregation based mechanisms, however, suffer from fundamental sensitivity limits and relatively slow kinetics. A sensor based on the disassembly of particles can overcome these limits, since the optical signal is obtained from free particles and the diffusion of free DNA is faster than that of nanoparticle-bound DNA. The catalytic disassembly of nanoparticles is driven by an autocatalytic network developed by Zhang et al. As illustrated in Figure 1, the substrate complexes of the network act as a link between gold nanoparticles and polymer microbeads. In the presence of catalyst and fuel, the substrate dissociates into waste and output, which causes a change in solution color. The substrate, nanoparticle coated beads, was assembled first to control the size and shape of gold nanoparticle aggregates. Preliminary results indicate a DNA target as low as 1 nM could be detected using the sensing mechanism. To improve the sensitivity of the mechanism, the effect of surface DNA strands, nanoparticle and microbead sizes, and ionic strength will be investigated. The effect and reduction of leak in the system will also be explored using mismatched fuel strands to further increase sensitivity.

Colorimetric detection of DNA via catalytic release of polymer bead-immobilized gold nanoparticles

255th National Meeting (2018)

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