Patent ID: 6984491

Claim:
A method of detecting nucleic acid in a sample, the nucleic acid having at least two portions, said method comprising: providing a substrate having oligonucleotides attached thereto, the oligonucleotides having a sequence complementary to a first portion of the sequence of a nucleic acid to be detected; providing a scattered light detectable nanoparticle probe having oligonucleotides attached thereto, the oligonucleotides bound to the nanoparticle probe having a sequence complementary to a second portion of the sequence of said nucleic acid wherein the oligonucleotides are attached to the nanoparticles in a stepwise ageing process comprising (i) contacting the oligonucleotides with the nanoparticles in a first aqueous solution for a period of time sufficient to allow some of the oligonucleotides to bind to the nanoparticles; (ii) adding at least one salt to the aqueous solution to create a second aqueous solution; and (iii) contacting the oligonucleotides and nanoparticles in the second aqueous solution for an additional period of time to enable additional oligonucleotides to bind to the nanoparticles; contacting said nucleic acid, the substrate and the nanoparticle probe under conditions effective to allow hybridization of said nucleic acid with the oligonucleotides on the nanoparticle probe and with the oligonucleotides on the substrate and form a light scattering complex bound to the substrate; illuminating the light scattering complex under conditions effective to produce scattered light from said complex; detecting the light scattered by said complex under said conditions as a measure of the presence of the nucleic acid.