Point-of-care genetic diagnostic devices require a rapid, inexpensive, sensitive and selective detection platform. Two commercialized technologies developed in the past decade, real-time PCR and DNA microarrays, provide high sensitivity, but have significant drawbacks including complexity, high cost and sensitivity to environmental contaminants. These drawbacks are related to fluorescent reporting/detection and hinder them from being applied in the field.Colorimetric or plasmonic assays with ssDNA-induced nanoparticle self-assembly have achieved three times higher selectivity than conventional fluorescent reporting and 100 times higher sensitivity by silver reduction. In addition, nanoparticle aggregation is found to be more stable and robust than fluorescence assays for field samples with uncertain pH and ionic strengths. However, nanoparticle assays suffer from long assay times due to the long particle diffusion time and low sensitivity without the tedious silver reduction enhancement. In our current design, these limitations are overcome by using an AC electric field to accelerate ssDNA-induced self-assembly of probe functionalized nanoparticle probes with 10-nm gold-coated tips of optical fiber cone arrays, where the electric field is intensified because of the lightning-rod effect at the conic singularity. The intense induced nanoparticle dipole that results imparts a pN dielectrophoretic force on the particle towards the cone tip, thus reducing the particle transport time from hours to minutes. Enhanced plasmon resonance at cone tip interacts with nanoparticle plasmon resonance, thus producing enhanced plasmonic signal of the nanoparticle reporters, without fluorophores or silver reduction.The nanocolloid-cone array assay hence offers sensitivity, robustness, rapid assay time etc and can be used with a small and simple portable instrumentation---a miniature camera suffices as the optical detector for the entire array.

Plasmonic nucleic acid sensing by target-induced nanoparticle self-assembly onto optical fiber cone arrays

246th National Meeting (2013)

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