title: Three-layer composite magnetic nanoparticle probes for DNA.
abstract: A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell.
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
authors.forename: Savka I
authors.initials: SI
authors.lastname: Stoeva
authors.forename: Fengwei
authors.initials: F
authors.lastname: Huo
authors.forename: Jae-Seung
authors.initials: JS
authors.lastname: Lee
authors.forename: Chad A
authors.initials: CA
authors.lastname: Mirkin
mesh_terms: D004247:DNA / Q000032:analysis; D015342:DNA Probes / Q000138:chemical synthesis*; D005296:Ferrous Compounds; D006046:Gold; D006358:Hot Temperature; D008280:Magnetics; D049329:Nanostructures; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides
chemical_list: D015342:DNA Probes; D005296:Ferrous Compounds; D009841:Oligonucleotides; D006046:Gold; D004247:DNA; C034236:ferrous oxide