Patent ID: 7238472

Claim:
A method for making core/shell nanoparticle oligonucleotide conjugates comprising (a) providing core/shell nanoparticles comprising magnetic cores and non-alloying gold shells surrounding the magnetic cores, the gold shells having a predetermined thickness and the core/shell nanoparticle having a mean diameter ranging from 5 to 150 nm, wherein the core/shell nanoparticles are prepared by treating the magnetic cores by simultaneous addition of a solution comprising a gold salt and a solution comprising a reducing agent so as to form a reaction mixture having a gold salt concentration of about 2 uM; and (b) contacting the oligonucleotides with the core/shell nanoparticles in a first aqueous solution for a period of time sufficient to allow some of the oligonucleotides to bind to the nanoparticles; (c) adding at least one salt to the aqueous solution to create a second aqueous solution; and (d) 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.