Gold nanoparticle aggregation for quantification of oligonucleotides: optimization and increased dynamic range.

A variety of assays have been proposed to detect small quantities of nucleic acids at the point of care. One approach relies on target-induced aggregation of gold nanoparticles functionalized with oligonucleotide sequences complementary to adjacent regions on the targeted sequence. In the presence of the target sequence, the gold nanoparticles aggregate, producing an easily detectable shift in the optical scattering properties of the solution. The major limitations of this assay are that it requires heating and that long incubation times are needed to produce a result. This study aimed to optimize the assay conditions and optical readout, with the goals of eliminating the need for heating and reducing the time to result without sacrificing sensitivity or dynamic range. By optimizing assay conditions and measuring the spectrum of scattered light at the end point of incubation, we found that the assay is capable of producing quantifiable results at room temperature in 30min with a linear dynamic range spanning 150amol to 15fmol of target. If changes in light scattering are measured dynamically during the incubation process, the linear range can be expanded 2-fold, spanning 50amol to 500fmol, while decreasing the time to result to 10min.