title: Surface modification of gamma-Fe2O3@SiO2 magnetic nanoparticles for the controlled interaction with biomolecules.
abstract: Modifying the surface of magnetic nanoparticles (MNPs) to allow for controlled interaction with biomolecules enables their implementation in biomedical applications such as contrast agents for magnetic resonance imaging, labels in magnetic biosensing or media for magnetically assisted bioseparation. In this paper, self-assembly of trialkoxysilanes is used to chemically functionalize the surface of gamma-Fe2O3@SiO2 core-shell particles. First, the silane deposition procedure was optimized using infrared analysis in order to obtain maximum packing density of the silanes on the particles. The surface coverage was determined to be approximately 8 x 10(14) molecules/cm2. It was shown that the magnetic, crystalline, and morphological properties of the MNPs were not altered by deposition of a thin silane coating. The optimized procedure was transferred for the deposition of aldehyde and poly(ethylene glycol) (PEG) presenting silanes. The presence of both silanes on the particle surface was confirmed using XPS and FTIR. The interaction of proteins with silane-modified MNPs was monitored using a Bradford protein assay. Our results demonstrate that, by introducing aldehyde functions, the MNPs are capable of covalently binding human IgG while retaining their specific binding capacity. Maximum surface coverage occurs at 46 microg antibodies per mg particle, which corresponds to 35 antibodies bound to an average sized MNP (54 nm in diameter). The human IgG functionalized MNPs exhibit a high degree of specificity (approximately 90%) and retained a binding capacity of 32%. Using the same approach, streptavidin was coupled onto the MNPs and the biotin binding capacity was determined using biotinylated fluorescein. At maximum surface coverage, a biotin binding capacity of 1500 pmol/mg was obtained, corresponding to a streptavidin activity of 76%. On the other hand, by introducing PEG functions the non-specific adsorption of serum proteins could be significantly suppressed down to approximately 3 microg/mg. We conclude that self-assembly of silane films creates a generic platform for the controlled interactions of MNPs with biomolecules.
authors.affiliation: IMEC, NEXT Kapeldreef 75, B-3001 Leuven, Belgium.
authors.forename: Randy
authors.initials: R
authors.lastname: De Palma
authors.forename: Jesse
authors.initials: J
authors.lastname: Trekker
authors.forename: Sara
authors.initials: S
authors.lastname: Peeters
authors.forename: Margriet J
authors.initials: MJ
authors.lastname: Van Bael
authors.forename: Kristien
authors.initials: K
authors.lastname: Bonroy
authors.forename: Roel
authors.initials: R
authors.lastname: Wirix-Speetjens
authors.forename: Gunter
authors.initials: G
authors.lastname: Reekmans
authors.forename: Wim
authors.initials: W
authors.lastname: Laureyn
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Borghs
authors.forename: Guido
authors.initials: G
authors.lastname: Maes
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D000818:Animals; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D053768:Metal Nanoparticles; D051379:Mice; D012822:Silicon Dioxide / Q000737:chemistry*; D019809:Streptavidin / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000447:Aldehydes; D005290:Ferric Compounds; D007074:Immunoglobulin G; C000499:ferric oxide; D012822:Silicon Dioxide; D019809:Streptavidin