title: Multiple morphologies of gold-magnetite heterostructure nanoparticles are effectively functionalized with protein for cell targeting.
abstract: Nanoparticles composed of a magnetic iron oxide core surrounded by a metal shell have utility in a broad range of biomedical applications. However, the presence of surface energy differences between the two components makes wetting of oxide with metal unfavorable, precluding a "core-shell" structure of an oxide core completely surrounded by a thin metal shell. Three-dimensional island growth followed by island coalescence into thick shells is favored over the two-dimensional layer-by-layer growth of a thin, continuous metal coating of a true core-shell. Aqueous synthesis of gold-coated magnetite nanoparticles with analysis by infrared, energy-dispersive X-ray, and electron energy loss spectroscopies; high-resolution transmission electron microscopy; selected area electron diffraction; and high-angle annular dark-field scanning transmission electron microscopy showed two distinct morphologies that are inconsistent with an idealized core-shell. The majority were isolated ~16-22-nm-diameter nanoparticles consisting of ~7-nm-diameter magnetite and a thick deposition of gold, most often discontinuous, with some potentially "sandwiched" morphologies. A minority were aggregates of agglomerated magnetite decorated with gold but displaying significant bare magnetite. Both populations were successfully conjugated to fibrinogen and targeted to surface-activated platelets, demonstrating that iron oxide-gold nanoparticles produced by aqueous synthesis do not require an ideal core-shell structure for biological activity in cell labeling and targeting applications.
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201-0413, USA.
authors.forename: Evan S
authors.initials: ES
authors.lastname: Krystofiak
authors.forename: Eric C
authors.initials: EC
authors.lastname: Mattson
authors.forename: Paul M
authors.initials: PM
authors.lastname: Voyles
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Hirschmugl
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Albrecht
authors.forename: Marija
authors.initials: M
authors.lastname: Gajdardziska-Josifovska
authors.forename: Julie A
authors.initials: JA
authors.lastname: Oliver
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D052203:Ferrosoferric Oxide / Q000737:chemistry / Q000378:metabolism*; D005340:Fibrinogen / Q000737:chemistry / Q000378:metabolism*; D006046:Gold / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D006046:Gold; D005340:Fibrinogen; D052203:Ferrosoferric Oxide